Patient education intervention to improve diversity in breast cancer clinical trials

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Background: Patient education has been shown to improve clinical trial participation. Medically underserved, racial, and ethnic minorities have a lower participation rate in cancer clinical trials (CCT) than patients of high socioeconomic status (SES). Our comprehensive cancer center is notable for providing equal access to breast CCT (BCCT) through a private system (McNair) and a public safety net hospital system, Smith Clinic (SC). Our prior research has shown that SC cancer patients, who are 60% uninsured, predominantly low SES, and >80% racial minorities, are 40% less likely to enroll into BCCT compared to McNair patients who are > 95% insured and largely White. Methods: We developed a 7-minute video with testimonies of our current patients (who are of diverse racial and linguistic backgrounds) about their BCCT experience and testimonies of our research team discussing misconceptions surrounding BCCT and biospecimen collection. The video was designed to be culturally sensitive and used simplified terms in English, Spanish, and Vietnamese. We modified a validated questionnaire by UT Health San Antonio, Institute for Health Promotion Research to assess participants’ attitudes towards CCT participation before and after watching the video. We used a Wilcoxon Signed Rank test to measure the effect of the video on a 5-point Likert scale with 5 indicating “Extremely likely”, 3 “Moderately Likely” and 1 “Not Likely at all”. The primary outcome was a shift in likelihood of participation in a CCT by 1. Other outcomes included assessing the effects of English proficiency, residing in United States (US) for at least 10 years, race, stage of breast cancer diagnosis (high risk vs. early stage vs. metastatic disease) using Chi-squared tests. With 200 survey respondents, the study had 97% power to detect the desired primary outcome. The project was supported by a Pfizer education grant. Results: A total of 200 patients (73 at McNair and 127 at SC) watched the video and completed the surveys. 93 identified as Hispanic, 50 as African American, 14 as Asian, 47 as White, and 7 as other races. The mean pre-intervention score for likelihood of willingness to participate in a CCT was 3.34 (SD 1.45) at McNair and 2.81 (SD 1.28) at SC. The mean post-intervention score was 3.89 (SD 1.28) at McNair and 3.44 (SD 1.22) at SC. While the pre- and post-intervention scores were significantly different across the two sites (p = 0.01 and p = 0.015 respectively), the study did not meet its primary objective. English proficiency, residing in US for at least 10 years, race, and stage of breast cancer diagnosis were not significantly associated with the outcome. Conclusions: Our patient education video did not improve our patients’ willingness to participate in BCCT as much as we had hoped. This suggests that a comprehensive approach is required to improve our community’s engagement and close the disparity gap in BCCT enrollment.

Targeting kinome reprogramming in ESR1 fusion-driven metastatic breast cancer

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Background: Genomic analysis has recently identified multiple ESR1 gene translocations in estrogen receptor-alpha positive (ERα+) metastatic breast cancer (MBC) that encode chimeric proteins whereby the ESR1 ligand binding domain is replaced by C-terminal sequences from many different gene partners. Transcriptionally active ESR1 fusions promoted hormone-independent cell growth, motility and resistance to endocrine therapy. The diversity of partner genes creates a considerable diagnostic challenge and no targeted treatments exist for ESR1 translocated tumors. Thus, we have established a transcriptional signature to diagnose the presence of an active ESR1 fusion (PMID: 34711608) and developed novel targeted therapies against ESR1 fusion-driven biology. Methods: Fifteen ESR1 fusion cDNA constructs were expressed in ER+ breast cancer cell lines by lentiviral transduction. Cell growth was assayed by Alamar blue assay. A mass spectrometry (MS)-based Kinase Inhibitor Pulldown Assay (KIPA) and tandem mass tag-based proteomics were performed to identify ESR1 fusion-driven druggable kinases for subsequent pharmacological inhibition. Results: KIPA profiling demonstrated an increase of multiple receptor tyrosine kinases including RET in T47D cells expressing active ESR1 fusions. Inhibition of RET by repurposing an FDA-approved drug significantly suppressed ESR1 fusion-driven cell growth in vitro, suggesting that despite marked diversity in the 3’ partners, common kinase activities were elevated and targetable. Proteogenomic profiling, including whole exome sequencing, RNA sequencing, and MS-based proteomics and phosphoproteomics were further performed on 22 ER+ patient-derived xenograft (PDX) tumors, which demonstrated different degrees of estradiol dependence. These integrated “omic” profiles defined targetable genes/pathways and predict tumor subsets that could be responsive to kinase inhibition therapy from this biologically heterogeneous panel of PDX tumors. WHIM18, a PDX naturally harboring the ESR1-YAP1 fusion showed elevated level of RET and CDK4/6 pathways. The tumor volumes were significantly reduced by the RET inhibitor. CDK4/6 inhibitor treatment showed similar tumor reductions to RET inhibition. Interestingly, WHIM9 PDX that expressed wild-type ESR1 conferred a comparable kinome profile to WHIM18. The tumor growth was significantly suppressed by RET or CDK4/6 inhibition. Therefore, pharmacological experiments validated proteogenomics-predicted drug response in two tested ER+ PDX models. Conclusions: Proteogenomics characterization of PDX tumors can drive clinical trial hypotheses. Here, we reveal therapeutic kinase vulnerabilities in ESR1 fusion-driven tumors as exemplified by RET inhibition, which will lay the framework for future clinical trials.

Patient education intervention to improve breast cancer clinical trials participation

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Background: Patient education has been shown to improve clinical trial participation. Medically underserved, racial, and ethnic minorities have lower participation rate in cancer clinical trials (CCT) than patients of high socioeconomic status (SES). Our comprehensive cancer center is notable for providing equal access to breast CCT through a private system (Baylor McNair) and a public safety net hospital (Harris Health Smith Clinic). Our prior research has shown that breast cancer patients at Smith Clinic (SC) who are 60% uninsured, predominantly of low SES, and 80% racial and ethnic minorities are 40% less likely to enroll compared to McNair patients where patients are > 95% insured and largely Caucasian. Methods: We developed a 7-minute video consisting of current patients’ testimonies of their CCT experience along with the research team discussing misconceptions regarding CCT and biospecimen collection. The video was designed to be culturally sensitive and used simplified terms in English, Spanish, and Vietnamese. We modified a validated questionnaire by UT Health San Antonio, Institute for Health Promotion Research to assess participants attitudes towards CCT participation before and after watching the video. We used a Wilcoxon Signed Rank test for measuring the effect of the video on a 5-point Likert scale with 5 indicating “Extremely likely”, 3 “Moderately Likely” and 1 “Not Likely at all”. The primary outcome was a shift in stated likelihood of participation in a CCT by 1 point. Using Chi-squared test, we assessed whether English proficiency or residing in the United States (US) for more than 10 years affected the results. Patients’ reason for refusing CCT was documented. With 200 survey responders, the study had 97% power to detect the desired primary outcome. The project was supported by a Pfizer education grant. Results: A total of 200 patients (73 at McNair and 127 at SC) watched the video and completed the surveys. The mean pre-intervention score for likelihood of willingness to participate in a CCT was 3.34 (SD 1.45) at McNair and 2.81 (SD 1.28) at SC. The mean post-intervention score was 3.89 (SD 1.28) at McNair and 3.44 (SD 1.22) at SC. While the pre- and post- intervention scores were significantly different across the two sites (p = 0.01 and p = 0.015 respectively), the study did not meet its primary objective. There were also no significant differences in the willingness to participate in CCT with regards to time spent in the US or English proficiency. Most frequent reasons for refusal were concern about extra costs, extra time commitment and the need to discuss the trial with family members. Conclusions: Our in-house developed patient education video did not improve patients’ willingness to participate in CCT as much as we had hoped. This suggests that a comprehensive approach is required to improve our community’s engagement and close the disparity gap in the treatment and outcomes of breast cancer.

Evaluation of sensitivity to endocrine therapy index (SET2,3) for response to neoadjuvant endocrine therapy (NET) and subsequent prognosis

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Background: Patients (pts) in Cohort A of the American College of Surgeons Oncology Group Z1031 (Alliance) trial of NET for cStage II-III breast cancer were randomized to anastrozole [ANA], letrozole [LET] or exemestane [EXE] for 16-18 weeks (wks). In Cohort B, pts chose between ANA and LET and switched to chemotherapy or surgery if a tumor biopsy after 2-4 wks of NET had Ki67 >10%. Treatments after surgery were not defined by the trial protocol. SET2,3 measures nonproliferation gene expression related to estrogen and progesterone receptors adjusting for a baseline prognostic index that combines clinical tumor and nodal stage and a 4-gene molecular subtype (RNA4) defined by ESR1, PGR, ERBB2 and AURKA. High SET2,3 in a pre-treatment biopsy using cStage information is defined as SET2,3 >1.77. Methods: 379 pts had gene expression data from a research tumor biopsy prior to NET (Agilent 44K microarrays). A bioinformatician blinded to pt treatment and clinical outcomes determined SET2,3. The trial statistician then examined the association between SET2,3 and pharmacodynamic response at 2-4 wks (N=141, Cohort B): Ki67 ≤10% and complete cell cycle arrest (CCCA Ki67 ≤2.7%); pathologic outcomes in pts who completed NET: ypStage 0/1 (N=329, Cohorts A&B), PEPI-0 rate (N=155, Cohort B); and event-free survival (EFS) post-registration (N=244, Cohorts A&B). We used Fisher’s exact tests to assess whether responses, and Cox modeling to evaluate whether EFS, differed with respect to SET2,3 status. Results: High SET2,3 in 48% of pts (183/379) was associated with older age (median: 66 vs 63 years; p=0.012); cStage II (95% vs 75%; p <0.001); and pre-NET Ki67 ≤10% (37% vs 20%; p< 0.001) in pts with low SET2,3. In Cohort B, pts with high SET2,3 had a higher rate of pharmacodynamic response in their tumor at wk 2-4 than pts with low SET2,3 (Table). In the subset of Cohort B pts with wk 2-4 Ki67 ≤10%, pre-treatment SET2,3 trended numerically higher in pts who achieved PEPI-0 score (p=0.049) but the proportion achieving PEPI-0 did not differ by SET2,3 high/low status (Table). EFS was significantly longer for pts with high SET2,3 than pts with low SET2,3 (HR[H/L]: 0.52; 95% CI: 0.34-0.80; p=0.003). Conclusions: An exploratory analysis of Z1031 data demonstrated that the rate of pharmacodynamic suppression of proliferation by NET at 2-4 wks was greater and EFS was longer for pts with breast cancer expressing high SET2,3 disease than pts with low SET2,3. Support: U10CA180821, U10CA180882, U24CA196171; https://acknowledgments.alliancefound.org ; Clinical trial information: NCT00265759. [Table: see text]

Change in management based on actionable mutations in metastatic breast cancer in an ethnically diverse cohort: Single institution experience

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Background: Recently, next generation sequencing (NGS) has been used with increasing frequency to guide therapy decisions for patients with metastatic solid tumors. NGS is a DNA sequencing technology that detects somatically acquired mutations. If an actionable mutation is identified, it may affect prognosis and guide therapy. At our institution we serve a large proportion of minority and underserved patients and analyzed their NGS results to determine if there was a change in management. Methods: Patients with metastatic breast cancer treated at one of two sites at Baylor College of Medicine who underwent NGS via Tempus between 2018-2020 were included. Tempus provided access to the variant database for these patients. We analyzed the charts of 43 patients who underwent NGS via Tempus on tissue, blood or both. In those patients with clinically actionable mutations, we noted if there was a change in management. Utilizing Redcap, we extracted demographics, sites of metastasis, biomarker activity and site, genomic sequencing, and duration and sequencing of therapies given along with clinical trial information. Results: Of the 43 patients included in this analysis, the mean age was 55 years, 33% were African American, 30% were Hispanic, 21% were white/non-Hispanic, 12% were Asian, 4% were other. Two thirds of patients were treated in the Harris Health System (a safety net hospital with a unique and diverse population) while one third was treated at the Baylor St. Luke’s Medical Center (a private academically affiliated institution). Of the 43 patients, 14 had PIK3CA mutations and 3 had a change in management. 2 patients had microsatellite instability (MSI) and received immunotherapy, and 1 patient had a HER2 mutation and entered a clinical trial with Neratinib. Additionally, 2 patients were incidentally found to have MUTYH germline mutation which is associated with polyposis. Conclusions: With increasing frequency, patients with metastatic malignancy undergo NGS in order to determine if there is an actionable mutation that can guide their next line of treatment. However, this technology could be cost prohibitive for many underserved patients. Our study analyzes a unique and diverse population of patients, many of whom are underserved. We were able conduct this testing in our cohort, study the frequency of somatic mutations and monitor for change in treatment. Of the variants analyzed, PIK3CA mutations are actionable and patients can receive Alpelisib + Fulvestrant- however many did not. There was not a large shift in management based on the incorporation of this DNA sequencing technology which suggests that, unlike the case of other solid tumors, there aren’t yet as many actionable targets for patients with metastatic breast cancer. Shared decision making along with consideration of cost is paramount for these patients as we shift into an era of highly personalized medicine.

ALTERNATE: Neoadjuvant endocrine treatment (NET) approaches for clinical stage II or III estrogen receptor-positive HER2-negative breast cancer (ER+ HER2- BC) in postmenopausal (PM) women: Alliance A011106

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Background: For PM patients (pts) with locally advanced ER+ HER2- BC, NET improves breast conservation surgery (BCS) rates, and modified preoperative endocrine prognostic index (mPEPI) 0, defined as pT1-2 pN0 Ki67< 2.7%, or pathologic complete response (pCR: no invasive disease in breast or lymph node) is associated with low risk of recurrence without adjuvant chemotherapy (CT). The ALTERNATE trial was initiated to assess if the endocrine-sensitive disease rate (ESDR: number of mPEPI 0 pts/number of eligible pts initiating NET) with fulvestrant (F) or F+anastrozole (A) is improved relative to A alone (reported here) and if the 5-year (yr) recurrence-free survival (RFS) rate for pts with mPEPI 0 on A alone without CT is ≥ 95% (awaits further follow-up). Methods: PM pts with clinical stage II/III ER+ HER2- BC were randomized 1:1:1 to 1 mg A po daily, 500 mg F IM every 4 week (wk)s after loading dose, or A+F for 6 months. Ki67 was tested centrally on biopsies acquired prior to NET, wk 4, wk 12 and at surgery. Pts with Ki67 >10% at wk 4 or 12 were recommended to go off protocol-directed ET and switch to CT. Pts with mPEPI 0 at surgery were recommended to continue assigned ET for 1.5 yrs followed by A for a total of 5 yrs ET (and not to receive CT). The primary endpoint of the neoadjuvant phase was ESDR. ESDR of each F arm was compared to that of the A alone arm. With 425 pts per arm, a one-tailed alpha = 0.025 chi-square test of two independent proportions has 84% power to detect an increase of ≥10% in ESDR for F or F+A compared to the A arm, assuming ESDR ≤30% in A. Results: 1362 pts (A 452; F 454; A+F 456) were enrolled Feb 2014 to Nov 2018. 63 pts were excluded (did not start NET). Of the remaining 1299 pts (A 434; F 431, A+F 434), 42% were cN1-3 and 73% were considered candidates for BCS. ESDR was 18.6% (95%CI: 15.1-22.7%) with A, 22.7% (95%CI: 18.9-27.0%) with F, and 20.5% (95%CI: 16.8-24.6%) with A+F. No significant difference in ESDR was found between A and F (p=0.15) or A and A+F (p=0.55). Among the 825 pts with wk 4 Ki67 < 10% who completed NET and surgery, ESDR and the BCS rate were 27.7% and 70.3% with A; 29.6% and 68.1% with F, and 26.8% and 69.9% with A+F, respectively. Conclusion: Neither F nor F+A significantly improved ESDR compared to A alone in PM pts with locally advanced ER+ HER2- BC. RFS data are awaited. Support: U10CA180821, U10CA180882, U24CA196171, https://acknowledgments.alliancefound.org ; NCI BIQSFP, BCRF, Genentech, AstraZeneca. Clinical trial information: NCT01953588 .

Abstract TS1-3: Proteogenomics and Clinical Translation

Improvements in breast cancer treatment are being achieved at an increasing pace in all three clinical subsets of the disease, namely ER+ HER2- (luminal), HER2+ (HER2-driven) and ER- PgR- and HER2- (triple negative). While these disease groupings served as useful approximations of the immense diversity of breast cancer when only endocrine therapy, chemotherapy and trastuzumab were available, the inadequacy of this disease classification is readily evident when set against the sophistication of our growing therapeutic armamentarium. What is on the horizon to replace our simple immunohistochemistry-based subtyping approaches to avoid misdiagnosis and consequent mismanagement? In this lecture I will make the argument that the advent of efficient and accurate protein mass spectrometry provides the “missing link” in ‘omics analysis that integrates information derived from next generation DNA and RNA analysis to create a more secure diagnostic conclusion. The new field of “clinical proteogenomics” validates proposed disease drivers, dissects complex amplicons, monitors signaling perturbations in response to targeted treatments and determines the activity of the immune microenvironment. The advent of cloud computing promotes the efficient delivery of individualized proteogenomic therapeutic road maps as a near-term possibility.

Citation Format: MJ Ellis. Proteogenomics and Clinical Translation [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr TS1-3.

Abstract BL2: The Molecular Etiology of Luminal-Type Breast Cancer

Estrogen receptor positive disease is the dominant contributor to global deaths from breast cancer which now exceeds 500,000 deaths annually. Lethality is driven by endocrine therapy resistance, the development of metastasis and an inability of the immune system to mount an effective anti-tumor T cell response. While our understanding of these processes is incomplete, molecular analyses of ER+ tumor samples accrued from patients undergoing neoadjuvant endocrine therapy (NET) have generated fundamental insights into nature of the disease while providing clear benefits to patients in terms of increased use of breast conserving surgery and strategies to avoid chemotherapy1,2. From the outset, genomic analyses of ER+ breast cancer samples has demonstrated that poor outcome is associated with genomic complexity and sub-clonal diversity3,4. As endocrine therapy responsive tumors are exposed to treatment, responsive subclones regress and resistant subclones expand. Eventually clones harboring lethal mutations are selected, including ER ligand binding mutations and chromosomal translocations involving ER that generate EMT-driving chimeric transcription factors5,6. Additional genomic events include loss of tumor suppressors that deregulate ER function, such as NF1 frame-shift or nonsense mutations7, or gain of function mutations in growth factor receptors such as ErbB28. These acquired resistance mutations are druggable and targeted interventions should prove useful. But what are the DNA repair defects that underlie the lethal genomic complexity of ER+ disease? Unlike ER negative/basal like breast cancer, luminal-type breast cancer is typically not defective in homologous recombination and is TP53 wild-type. Our recent data suggest loss of components in single strand (ss) DNA repair mechanisms associate with poor prognosis in ER+ breast cancer including MLH1/PMS1/PMS2 (mismatch repair), NEIL2 (base excision repair) or ERCC1 (nucleotide excision repair)9,10. Experimental down-regulation of any of these five genes generates endocrine therapy resistance, likely by disrupting CHK2 signaling, which acts as an endogenous inhibitor of CDK4/6 function. Indeed, direct CHK2 knockdown also generates endocrine therapy resistance but CDK4/6 inhibitor sensitivity is maintained in all these experimental conditions. Essentially the CDK4/6 inhibitor therapy can be seen as replacing CHK2 for negative cell cycle regulation. Thus, we postulate that the presence of ssDNA break repair defects and/or CHK2 dysregulation could underlie the remarkably selective efficacy of CDK4/6 inhibitors in ER+ disease by targeting the intersection of ER signaling and the ssDNA repair response at the level of CHK2 activity. Furthermore, correlations between poor prognosis in ER+ disease, increased innate immunity signaling and ssDNA repair defects point towards subsets of ER+ breast cancers that might respond to immune checkpoint therapy11. References: 1. J Clin Oncol 29, 2342, (2011).2. J Clin Oncol 35, 1061, 2017, 3. Nat Commun 7, 12498, (2016) 4. Nature 486, 353 (2012). 5. Cell Rep 4, 1116, 2013. 6. Cell Rep 24, 1434-2018. 7. Nat Commun 9, 3476, 2018. 8. Cancer Discov 3, 224, 2013. 9. Cancer Discov 7, 1168, 2017. 10. Clin Cancer Res 24, 4887, 2018. 11. JNCI in press.

Citation Format: MJ Ellis. The Molecular Etiology of Luminal-Type Breast Cancer [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr BL2.

Abstract P6-15-03: MBC Connect™, an open-access, patient-reported registry of de-identified data from patients living with metastatic breast cancer

Metastatic breast cancer (MBC) remains an incurable disease and is the cause of nearly all deaths from breast cancer. Several barriers prevent efficient research into various questions about living with MBC. A key unmet need is a national database for MBC patient-reported outcomes, which does not exist anywhere in the world. Furthermore, compartmentalized data prevents broad collaborative efforts. Treatment patterns and responses, survival times, and metastatic patterns are not documented systematically and remain unavailable. Large-scale data extraction is challenging, and expensive, and electronic medical records do not provide information regarding patient experiences. Methods: MBC Connect™ was created to help overcome these barriers. MBC Connect, which is sponsored by the Metastatic Breast Cancer Alliance, is a multi-national registry of participant reported information about their experience of MBC. MBC Connect allows MBC patients to voluntarily provide information about their disease, treatment outcomes, and experience of living with their disease so that researchers can gain insight into unmet needs in MBC. MBC Connect has three main goals: 1. Establish an interactive registry of patient-entered, de-identified data for MBC. 2. Create an open-access portal for researchers to study these data. 3. Create a connection between investigators of clinical trials and clinical research studies and registered users who may be interested in clinical trials. Results: MBC Connect collects, via the use of a mobile app (on a smartphone or tablet, iOS and Android compatible) or via a website for desktop users, participant consent, general patient characteristics and demographics, disease characteristics, genetics and tumor mutations, treatment history, quality of life data, and clinical trial experience. This information can be provided by patients living with MBC or their caregiver. The data are collected from responses to surveys and via creation of a treatment profile. The data are de-identified and made available on an open-access Researcher portal, allowing them to be used to advance multiple areas of research into MBC, including both medical treatment aspects and quality of life issues. An interactive feature of MBC Connect is that researchers may submit a request for participants to answer additional surveys. Participants may also be notified about clinical trials for which they may be eligible. In addition, participants will regularly receive “Insights,” which are engaging bytes of information related to MBC. Insights can offer general information about the disease, upcoming events, and other facts, or they can be personalized for the participant based on the information he or she has entered the registry. Conclusions: MBC Connect is a novel platform that aims to accelerate MBC research by providing open access to patient-reported, de-identified data about patients living with MBC. The overarching objective of this technologic initiative is to increase patient engagement with the research community.

Citation Format: Campbell L, De La Torre K, Williams CE, Mertz SA, Pollastro T, Hutton A, Newby J, Ellis MJ, Iyengar NM, Hurlbert MS. MBC Connect™, an open-access, patient-reported registry of de-identified data from patients living with metastatic breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-15-03.

Abstract P1-15-05: Is absolute lymphocyte count associated with platinum-sensitivity? A phase II single arm study evaluating the efficacy of neoadjuvant carboplatin and docetaxel in triple negative breast cancer

Background: Platinum-based chemotherapy is still considered investigational for the treatment of sporadic triple negative breast cancer (TNBC). Since patients with TNBC have a high rate of chemotherapy resistance, it is critical to identify platinum-sensitive individuals prior to initiating therapy. Higher absolute lymphocyte count (ALC) is associated with improved clinical response to anthracycline-based chemotherapy, the current standard of care in TNBC. We report the initial results of a phase II single arm study evaluating the efficacy of neoadjuvant carboplatin and docetaxel in TNBC. We also report results of an exploratory analysis assessing whether ALC can be used to predict pathologic complete response (pCR) after treatment with platinum-based chemotherapy.

Patients and Methods: 78 patients with clinical stage II or III TNBC have been enrolled in this ongoing study evaluating the efficacy of neoadjuvant carboplatin and docetaxel (NCT201404107). Patients received docetaxel 75 mg/m2 and carboplatin AUC 6 every three weeks for a total of 6 cycles. Blood samples were collected prior to each cycle, and a posttreatment sample was collected &gt; 3 weeks after completing cycle 6. pCR was defined as no residual invasive disease in the breast, with or without ductal carcinoma in situ, and no tumor deposits in sampled lymph nodes. Baseline characteristics of patients were summarized with descriptive statistics. Univariate and multivariate logistic regression analyses were used to identify factors associated with pCR.

Results: Out of the 78 enrolled patients, 60 have completed all 6 treatment cycles and surgery. The preliminary pCR rate is 46.7%. Age, race, clinical stage, and tumor grade determined at time of diagnosis were not significantly different between pCR patients and non-pCR patients. In univariate analyses, patients with higher ALCs at the posttreatment time point were more likely to have pCR than those who had lower ALCs (OR 5.5, 95% CI 1.5-20.7, p=0.011). Additionally, patients who had higher minimum ALCs were also more likely to have pCR (OR 9.1, 95% CI 1.5-54.9, p=0.016). Baseline ALC values were not associated with pCR. The associations of posttreatment and minimum ALCs to pCR remained statistically significant even after controlling for age and clinical stage at time of diagnosis (posttreatment ALC OR 7.6, 95% CI 1.7-34.8, p=0.009; minimum ALC OR 9.0, 95% CI 1.5-55.2, p=0.018).

Conclusion: The pCR rate of our cohort is similar to that of other trials evaluating neoadjuvant platinum-based chemotherapy in TNBC. Baseline ALC did not predict which patients would achieve pCR. However, the associations of posttreatment and minimum ALCs with pCR indicate patients who are able to maintain a robust population of circulating lymphocytes throughout treatment with platinum-based chemotherapy are more likely to respond favorably. The link between patient immunity and platinum-based chemotherapy suggests addition of immunotherapy agents to neoadjuvant chemotherapy may improve patient outcomes.

Citation Format: Chen I, Guo F, Summa T, Luo J, Ellis MJ, Ma CX, Weilbaecher KN, Naughton MJ, Suresh R, Peterson LL, Cherian MA, Bose R, Frith AE, Hernandez-Aya LF, Gillanders WE, Ademuyiwa FO. Is absolute lymphocyte count associated with platinum-sensitivity? A phase II single arm study evaluating the efficacy of neoadjuvant carboplatin and docetaxel in triple negative breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P1-15-05.

Abstract P6-17-15: Evaluating preclinical efficacy of anti-HER2 drug combinations using ER+/HER2 mutant models

Background

Until recently, HER2 gene amplification was the only mechanism of HER2 activation recognized. However, activating HER2 mutations have been noted in different cancer types. A trials of HER2 mutant breast cancer and the subsequent SUMMIT trial data have shown that monotherapy with the pan-HER drug neratinib as showed clinical efficacy, but with poor response durability. This study therefore investigates the preclinical efficacy of anti HER2 agents alone or in combination with endocrine therapy agents or in combination with CDK4/6 inhibitors using ER+/HER2 mutant cell lines and ex vivo HER2 mutant patient derived xenograft (PDX) model to define a more effective treatment approach.

Methods

ER+ breast cancer cell lines (T47D and MCF7) stably expressing HER2V777L, and ER+/HER2 mutant PDX model (HER2G778_P780 dup) were used to examine HER2 signaling and drug responses. Signaling downstream mutant HER2 was examined by immunoblot analysis. Effects of neratinib alone, neratinib + fulvestrant, and neratinib + abemaciclib on cell growth were examined in ER+/HER2 mutant cell lines and in an ex vivo HER2G778_P780 dup.

Results

We found that MCF7/T47D cells expressing HER2V777L and HER2G778_P780 dup PDX tumors showed strongly activated autophosphorylation of HER2 and increased expression of CDK4, CDK6, phospho-Rb, and cyclin D1 as compared to MCF7/T47D cells expressing HER2WT or ER+/non-HER2mut PDX modes, suggesting that HER2 mutations preferentially depend on CDK4/6 signaling for cell growth. Additionally, we showed that activating MCF7 HER2 V777L cause resistance to endocrine therapy treatment (fulvestrant IC50 &gt;5μM). Further, we show that neratinib alone is effective at higher concentrations (IC50 &lt; 2μM) in MCF7/HER2 V777L cells. We also demonstrate that abemaciclib alone exhibited moderate activity against MCF7 HER2 V777L cells (IC50 &lt; 0.4μM) and additional activity in combination with neratinib (IC50 &lt; 0.06μM) was seen. Moreover, ex vivo HER2 G778_P780 dup cells are relatively resistant to fulvestrant alone (IC50 &lt; 0.2μM), neratinib alone (IC50 &lt; 0.006μM), abemaciclib alone (IC50 &lt; 0.04μM), and neratinib in combination with abemaciclib (IC50 &lt; 0.005μM), suggesting that patients harboring ER+/HER2-mutant tumors may benefit from neratinib in combination with abemaciclib.

Conclusion

These preclinical data suggest that neratinib monotherapy may not be effective to treat ER+/HER2 mutant patients and we propose that simultaneous targeting of both HER2 and the CDK4/6 axis will be required for effective treatment of ER+ breast cancers harboring HER2 activating mutations.

Citation Format: Kavuri SM, Devarakonda V, Williams LC, Seker S, Lei JT, Singh P, Han A, Anurag M, Holloway KR, Welm AL, Ellis MJ. Evaluating preclinical efficacy of anti-HER2 drug combinations using ER+/HER2 mutant models [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-17-15.

Abstract P5-04-01: Functional and therapeutic significance of ESR1 fusions in metastatic ER+ breast cancer

Background. Next-generation sequencing methods have identified several ESR1 fusion genes in treatment refractory ER+ breast cancer, however detailed functional studies in experimental models are lacking and how they might be targeted remains poorly understood. We recently reported two transcriptionally active, in-frame ESR1 fusions, ESR1-YAP1 and ESR1-PCDH11X, identified in a small cohort of metastatic ER+ cases, that induce not only pan-endocrine therapy resistance but also metastatic disease progression (Lei et al., Cell Reports, in press). Limited characterization of ESR1-DAB2 and ESR1-GYG1, also identified in metastatic ER+ disease from a recent study, suggests these two ESR1 fusions also drive estrogen-independent gene activation (Hartmaier et al., Annals of Oncology, 2018). Here, we functionally characterize ESR1-DAB2 and ESR1-GYG1 along with additional ESR1 fusions discovered in metastatic ER+ breast tumors to further support a causal role for in-frame ESR1 fusions in driving endocrine therapy resistance and promoting metastasis-associated biology, and explore therapeutic vulnerabilities induced by ESR1 fusion gene formation.

Methods. RNA-seq identified ESR1 fusions from treatment refractory, ER+ metastatic breast tumors. In-frame ESR1 fusions constructs were generated and stably expressed in ER+ breast cancer cell lines: T47D, MCF7, and ZR75-1. Estrogen-independent and fulvestrant-resistant growth was monitored in hormone-deprived stable cell lines. mRNA-qPCR was performed to examine expression of estrogen responsive and epithelial-to-mesenchymal transition (EMT) genes. In vitro sensitivity to CDK4/6 inhibition was tested with palbociclib and abemaciclib.

Results. In addition to previously described ESR1-YAP1, ESR1-PCDH11X, ESR1-DAB2, and ESR1-GYG1, that follow a pattern retaining the first 6 exons of ESR1 (ESR1-e6) fused in-frame to C-terminal sequences provided by the partner gene, additional in-frame ESR1-e6 fusions, ESR1-PCMT1, ESR1-ARNT2, and ESR1-ARID1B, all identified in metastatic ER+ samples, were found to follow the same fusion pattern. ESR1-DAB2 and ESR1-GYG1 produced stable ESR1 fusion proteins in ER+ breast cancer cell lines. In T47D, these two fusions drove estrogen-independent and fulvestrant-resistant growth. In addition, T47D and ZR75-1 models revealed that ESR1-DAB2 drove estrogen-independent expression of estrogen responsive genes and also EMT genes, including SNAI1, suggesting this fusion, like ESR1-YAP1 and ESR1-PCDH11X, could also drive metastasis. Treatment with CDK4/6 inhibitors suppressed growth induced by ESR1-DAB2 and ESR1-GYG1.

Conclusion. The majority of in-frame ESR1 exon 6 fusions found in metastatic ER+ breast are transcriptionally active, drive endocrine therapy resistant proliferation, and induce an EMT-like transcriptional program. The ability to block ESR1 fusion induced growth with a CDK4/6 inhibitor is clinically significant as ESR1 fusion gene formation renders ER insensitive to all endocrine therapies that target the ligand binding domain. Furthermore, clinical diagnosis of an active ESR1 fusion could potentially stratify patients for CDK4/6 inhibitor treatment. This presentation is the most complete description of the role for ESR1 fusions in endocrine therapy resistance and metastasis described to date.

Citation Format: Lei JT, Gou X, Seker S, Haricharan S, Lee AV, Robinson DR, Ellis MJ. Functional and therapeutic significance of ESR1 fusions in metastatic ER+ breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P5-04-01.

Abstract PD7-08: Immune checkpoint upregulation and T-cell exhaustion in aggressive hormone-receptor positive breast cancer patients

Background: Early reports from studies focused on assessing the clinical efficacy for immune-checkpoint (IC) inhibitors in breast cancer suggest lower activity than in cancers caused by exogenous mutagens such as melanoma and smoking-related lung cancer. Nonetheless, triple negative breast cancer is under active investigation. In contrast, estrogen receptor positive disease has been considered “immunologically silent” with very few IC studies focused on this disease subset. We therefore undertook an analysis of ER+ breast cancer to determine if there are subsets of patients with poor prognosis ER+ disease that exhibit IC pathway upregulation hence potential candidates for IC-based clinical trials.

Methods: In an unbiased integrative analysis of patient samples, mRNA expression data for ˜15500 genes across 66 Luminal B patient set was used to identify genes for which the expression correlated positively with proliferation marker Ki67 (in aromatase-inhibitor treated tumors) and were upregulated (&gt;2 fold) in endocrine-therapy (ET) resistant samples as compared against the sensitive counterparts. Resulting genes were queried to identify underlying activated pathways and prioritize genes for further analysis. Validation of shortlisted genes was performed on independent patient cohorts (TCGA and METABRIC) using Kaplain-Meier disease-specific survival analysis. Amplification and methylation data for TCGA samples were obtained from CBioportal and Wanderer respectively. Proteomics data for TCGA samples was extracted using LikedOmics server. T-cell activation (TCA) and exhaustion (TCE) scores were devised using mean of standardized expression of genes reported to contribute in these two T cell states.

Result: Approximately 30 genes were found to be deferentially upregulated in ET-resistant aggressive ER+ breast cancer. This gene set was enriched in immune-tolerance biological processes (p&lt;0.005). The three immune-checkpoints constituting these processes are IDO1, LAG3 and PDCD1 (PD1). Upregulation of IDO1 was a confirmed poor prognosis factor across independent patient cohorts. Furthermore, comparative analysis of TCA and TCE scores between ET-resistant and sensitive tumors revealed that resistant tumors have high TCE, despite having high TCA, hence circumventing immunogenic apoptosis.

Conclusion: To date, no substantial study showing prognostic relevance of mRNA levels of ICs in context of ER+ breast cancer patients has been reported. Higher IDO1 and T-cell exhaustion levels in ET-resistant ER+ disease provides clinical evidence for a role for immune-checkpoints in evading immune-driven cell death. These results suggest a potential for IC targeted immunotherapy for ˜ 80% of endocrine therapy resistant clinically aggressive ER+ breast cancers.

Citation Format: Anurag M, Vasaikar S, Zhang X, Zhang B, Ellis MJ. Immune checkpoint upregulation and T-cell exhaustion in aggressive hormone-receptor positive breast cancer patients [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr PD7-08.

Abstract P5-04-30: Developing an immunohistochemistry protocol to detect neurofibromin as an effective, simple, and rapid method to identify NF1-negative breast cancer patients

Background:Neurofibromin is a key tumor suppressor, well-known as a GTPase-Activating-Protein (GAP) to attenuate Ras signaling. It is encoded by the NF1gene, so named because its inactivation was first discovered to cause Neurofibromatosis type 1, an autosomal dominant genetic disorder. We have recently reported thatnonsense (NS) and frameshift (FS) mutations, but not missense mutations, in NF1are associated with a markedly higher risk of relapse and death in early stage ER+breast cancer after adjuvant tamoxifen monotherapy (Griffith et al. in press). Surprisingly, despite being best known as a GAP, no missense mutations inactivating NF1's GAP activity were found in our cohort. We have evidence that these NF1NS/FS mutations cause the resulting mRNAs to be degraded, leading to depletion of the entire NF1 protein. In a separate study that was presented here last year, we showed that NF1 is also an ER co-repressor, which partially explains why the loss of the single tumor suppressor NF1 is so detrimental — because this turns on two potent oncogenic pathways. Thus far there is no effective means to assess loss of NF1 protein in cancer. The objective of this project is to identify these aggressive NF1-negative breast cancers by establishing an immunohistochemistry (IHC) protocol with a valid NF1 antibody in order to properly find and treat them in the future.

Methods:A monoclonal antibody was raised against the C-terminus of NF1. Immunostaining as well as IHC was performed using a set of breast cancer cell lines with varying degrees of NF1 protein levels, including several NF1 null-like cell lines as negative controls. To assess whether the IHC protocol can be used on patients, NF1+and NF1–PDXs as well as patient biopsies were examined.

Results: We have purified a monoclonal antibody against NF1 (m376). By immunostaining, a strong NF1 signal can be seen in T47D cells, which have four copies of the NF1gene. In contrast, there was barely any signal in MDA-MB-175VII cells, which lack detectable NF1 due to NF1FS mutations. While NF1 appears mostly cytoplasmic, 10-15% can be seen in the nucleus. Nuclear NF1 levels can be further increased by the nuclear export blocker leptomycin-B, suggesting that NF1 is shuttled in and out of the nucleus. IHC staining confirmed these features of NF1. In addition, a weak nuclear signal can be seen in cancer cells carrying NF1FS mutations. Experiments are on-going to assess how to analyze tumor samples for NF1 loss and whether NF1FS mutations cause expression of truncated proteins that are nuclear.

Conclusion: Our results suggest that the m376 antibody has the potential to be used for IHC, provided that samples known to be NF1+or NF1–are included as controls. The success of this project will have particular clinical impact in telling us who should notbe treated by tamoxifen. Furthermore, we have an approved clinical trial protocol to assess the concept that these NF1–patients should instead be treated by combining a Ras pathway inhibitor and a SERD.

Citation Format: Peng J, Zheng Z-y, Cakar B, Li J, Singh P, Szafrain AT, Stossi F, Dubrulle J, Mancini MA, Mao R, Miles G, Ellis MJ, Chang EC. Developing an immunohistochemistry protocol to detect neurofibromin as an effective, simple, and rapid method to identify NF1-negative breast cancer patients [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P5-04-30.

Abstract P5-08-01: DPYSL3 modulates mitosis, migration and epithelial to mesenchymal transition in claudin-low breast cancer

Proteogenomics is the field of integrating data from mass spectrometry-based shotgun proteomics, and phosphoproteomics into next-generation RNA and DNA sequencing data analysis pipelines that promises new insights into cancer biology and therapeutic targeting. As well as analyses of clinical samples for disease phenotype association analysis, the application of proteogenomics to model systems also has considerable potential. A Clinical Proteomic Tumor Analysis Consortium (CPTAC) proteogenomic analysis prioritized dihydropyrimidinase-like-3 (DPYSL3) as a multi-level (RNA/Protein/Phosphoprotein) expression outlier specific to the Claudin-Low (CLOW) subset of triple negative breast cancers. A Pubmed informatics tool indicated a paucity of data in the context of breast cancer which further prioritized DPYSL3 for study.

DPYSL3 was identified as a protein that is regulated during neuronal differentiation in the cerebral cortex and in neuronal cell lines and plays a role in regulating neurite outgrowth somehow through an association with vesicles in the growth cone. In addition, DPYSL3 expression has been observed in several malignant tumors, including prostate cancer, pancreatic cancer, gastric cancer and neuroblastoma. DPYSL3 is reported to play a role in cell migration and metastasis suppression in prostate cancer. However, in pancreatic cancer, DPYSL3 is positively associated with liver metastasis and poor outcome.

DPYSL3 knock-down in DPYSL3 (+) CLOW cell lines demonstrated reduced proliferation, yet enhanced motility and increased expression of Epithelial to Mesenchymal Transition (EMT) markers suggesting that DPYSL3 is a multi-functional signaling modulator. Slower proliferation in DPYSL3 (-) CLOW cells was associated with accumulation of multi-nucleated cells indicating a mitotic defect that was associated with a collapse of the vimentin (VIM) microfilament networkinduced by VIM hyperphosphorylation. On the other hand, DPYSL3 suppressed the expression of EMT regulators TWIST and SNAIL and opposed p21 activated kinase 2 (PAK2) dependent migration, but these EMT regulators in turn induced DPYSL3 expression, suggesting DPYSL3 participates in negative feedback in EMT. Cell migration in DPYSL3 (-) cells correlated with increased phosphorylation of PAK2 on Ser20 and was sensitive to PAK2 siRNA and pharmacological PAK inhibition.Immunoprecipitation and mass spectrometry-based proteomics or western blotting strongly suggests that PAKs interact such that DPYSL3 may function as a direct negative regulator of PAK family kinases. Thus, a PAK inhibitor could potentially mitigate increase migration as an adverse effect of DPYSL3 suppression.

In conclusion, DPYSL3 is a remarkable multifunctional signaling scaffold that should be examined further to provide insights into the stem cell-like state of claudin-low breast cancers, particularly in terms of their cell cycle dependencies, migratory activity and capacity for EMT.

Citation Format: Matsunuma R, Chan DW, Kim B-J, Singh P, Han A, Saltzman A, Cheng C, Lei JT, Sahin E, Leng M, Fan C, Perou CM, Malovannaya A, Ellis MJ. DPYSL3 modulates mitosis, migration and epithelial to mesenchymal transition in claudin-low breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P5-08-01.

Abstract P1-06-02: Mismatch repair protein loss in breast cancer: Clinicopathological associations in a large British Columbia cohort

Background: Alterations to mismatched repair (MMR) pathways are a known cause of cancer (particularly colorectal and endometrial). Recently, the FDA approved pembrolizumab for use in MMR-deficient (MMRD) cancers of any type, and the diagnosis can be made by immunohistochemistry (IHC) or genomic methods. In breast cancer, mutational process analyses indicate MMRD occurs in about 2% of breast cancer (Cancer Res; 77; 4755-62, 2017) and recent functional studies have shown associations with resistance to endocrine therapy and sensitivity to CDK4/6 inhibitors (Cancer Discov; 7; 1168-83, 2017). To date, insufficient cases have been assembled to power meaningful associative or survival studies. Herein, the strong correlation between IHC-determined loss of MLH1, PMS2, MSH2 or MSH6 and genomic evidence allowed the assessment of MMRD on a large tissue microarray (TMA) series linked to detailed biomarkers and long-term outcome data.

Methods: IHC markers MLH1, PMS2, MSH2 and MSH6 were optimized on the Ventana automated stainer for application to breast cancer TMAs. The patient cohort consists of females from British Columbia diagnosed with primary invasive breast carcinoma in 1986-1992, referred to the British Columbia Cancer Agency for treatment and follow-up. TMA blocks were sectioned and stained. Slides were scored by a pathologist and only nuclear positivity was evaluated positive. Loss of nuclear positivity for any one of the four tested marker defined MMRD. Clinicopathological associations were tested by Chi-square, and survival by Kaplan-Meier plot with log rank test.

Result: 1635 cases were interpretable for all MMR markers. 31 cases (1.9%) met criteria for MMRD. 6 cases had paired losses (4 MLH1-PMS2 loss, 2 MSH2-MSH6 loss) and the remaining 25 cases had singular MMR loss (11 PMS2 loss, 10 MLH1 loss, 3 MSH6 loss, 1 MSH2 loss). Deficiency of the the MutL complex (MLH1/PMS2) predominated over the MutS complex (MSH2/MSH6).

Among the demographic and pathological variables assessed – age, grade, tumour size, lymphovascular invasion, nodal and menstrual status – high grade is associated with MMRD (p=0.014). In terms of biomarker, MMRD is significantly associated with PR negativity (p=0.003) and PD-L1 expression (p=0.049), but not with ER, Her2, Ki67, or basal breast cancer IHC markers, nor does MMRD significantly correlate with any of the established major intrinsic subtypes of breast cancer. Tumor infiltrating lymphocyte (TIL) counts are higher in MMRD cases (p=0.009). Although statistically not significant (small numbers), Kaplan-Meier plots of survival analysis demonstrated a trend for MMR loss to be associated with decreased breast cancer disease-specific and overall survival.

Conclusion: This large series assessed by IHC corroborates findings from smaller genomic series that MMRD is present in about 2% of breast cancers. MMRD tumors are more likely to be high grade, low PR and immunologically active (higher PD-L1 expression and TIL counts). MMR deficiency is present across all major molecular subtypes (luminal, HER2, basal). Given the efficacy of PD1/PDL1 targeting agents in MMR deficient tumors of other types, evidence for the activity of these agents in MMR deficient breast cancers should be actively sought.

Citation Format: Cheng AS, Leung SC, Gao D, Anurag M, Nielsen T, Ellis MJ. Mismatch repair protein loss in breast cancer: Clinicopathological associations in a large British Columbia cohort [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P1-06-02.

Abstract GS4-07: Race, ethnicity and clinical outcomes in hormone receptor-positive, HER2-negative, node-negative breast cancer: results from the TAILORx trial

Background: Black race is associated with worse outcomes in localized hormone receptor (HR)-positive breast cancer in population-based and in clinical trial cohorts, whether using self-identified race (Albain et al. JNCI 2009 [PMID: 19584328; Sparano et al. JNCI 2012 [PMID: 22250182) or genetically-identified race (Schneider et al. J Precision Oncol 2017 [PMID: 29333527]). This disparity persists after adjustment for treatment delivery parameters (Hershman et al. JCO 2009 [PMID:19307504]). We evaluated clinicopathologic characteristics, treatment delivered and clinical outcomes in the Trial Assigning Individualized Options for Treatment (TAILORx) by race and ethnicity (Sparano et al. NEJM 2018 [PMID: 29860917]).

Methods: The analysis included 9719 evaluable TAILORx participants. The association between clinical outcomes and race (white, black, Asian, other/unknown) and ethnicity (Hispanic vs. non-Hispanic) was examined, including invasive disease-free survival (iDFS), distant relapse-free interval (DRFI), relapse-free interval (RFI), and overall survival (OS). Proportional hazards models were fit including age (5 categories), tumor size (&gt;2 cm vs. &lt;=2 cm), histologic grade (high vs. medium vs. low vs. unknown), continuous recurrence score (RS), race, and ethnicity in the overall population and randomized treatment arms in the RS 11-25 cohort.

Results: The study population included 8189 (84%) whites, 693 (7%) blacks, 405 (4%) Asians, and 432 (4%) with other/unknown race. Regarding ethnicity, 7635 (79%) were non-Hispanic, 889 (9%) Hispanic, and 1195 (12%) unknown. There was no significant difference in RS distribution (p=0.22) in blacks compared with whites, or in median (17 vs. 17) or mean RS (19.1 vs. 18.2). There was likewise no difference in Hispanic vs. non-Hispanic ethnicity for RS distribution (p=0.72) or median (17 vs. 17) or mean RS (18.5 vs. 18.0). Black race (39% vs. 30%) and Hispanic ethnicity (39% vs. 30%) were both associated with younger age (&lt;/=50 years) at diagnosis. The use and type of adjuvant chemotherapy and endocrine therapy, and duration of endocrine therapy, were similar in black (vs. white) and Hispanic (vs. non-Hispanic) populations. In proportional hazards models, black race (compared with white race) was associated with worse clinical outcomes in the entire population and in those with a RS 11-25 (see table). Hispanic ethnicity was generally associated with better outcomes (compared with non-Hispanic ethnicity). For the cohort with a RS of 11-25, there was no evidence for chemotherapy benefit for any racial or ethnic group.

Race (black vs.white) and clinical outcomes in proportional hazards modelsClinical endpointEntire Population (N=693 black) Hazard ratio for eventRS 11-25 (N=471 black) Hazard ratio for eveniDFS1.33 (p=0.005)1.49 (p=0.001)DRFI1.21 (p=0.28)1.60 (p=0.02)RFI1.39 (p=0.02)1.80 (p&lt;0.001)OS1.52 (p=0.005)1.67 (p=0.003

Conclusions: In patients eligible and selected for participation in TAILORx, black women had worse clinical outcomes despite similar 21-gene assay RS results and comparable systemic therapy. This adds to an emerging body of evidence suggesting a biologic basis or other factors contributing to racial disparities in HR-positive breast cancer that requires further evaluation.

Citation Format: Albain K, Gray RJ, Sparano JA, Makower DF, Pritchard KI, Hayes DF, Geyer, Jr. CE, Dees EC, Goetz MP, Olson, Jr. JA, Lively T, Badve SS, Saphner TJ, Wagner LI, Whelan TJ, Ellis MJ, Paik S, Wood WC, Ravdin PM, Keane MM, Gomez HL, Reddy PS, Goggins TF, Mayer IA, Brufsky AM, Toppmeyer DL, Kaklamani VG, Berenberg JL, Abrams J, Sledge, Jr. GW. Race, ethnicity and clinical outcomes in hormone receptor-positive, HER2-negative, node-negative breast cancer: results from the TAILORx trial [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr GS4-07.

Fulvestrant in management of hormone receptor-positive metastatic breast cancer

Fulvestrant is a steroidal selective estrogen receptor degrader that was approved by the US FDA in 2002 for treatment of ER-positive metastatic breast cancer (ER + MBC) post-progression on aromatase inhibitors. In 2017, the label was updated to include endocrine therapy naive ER + MBC. While initially fulvestrant was thought to be equivalent to aromatase inhibitors with monthly dose of 250 mg intramuscular injection, several postmarketing trials challenged this understanding. Subsequently, the recommended dose changed to 500 mg monthly plus loading dose, and this was proven to be superior to anastrozole in efficacy. Most recently the results of FALCON trial have further challenged the way fulvestrant is viewed and used. This report provides a historical perspective on this compound, its evolving role in management of ER + MBC and what the future may hold for this drug.

Genomic characterization of HER2-positive breast cancer and response to neoadjuvant trastuzumab and chemotherapy-results from the ACOSOG Z1041 (Alliance) trial

Background

HER2 (ERBB2) gene amplification and its corresponding overexpression are present in 15-30% of invasive breast cancers. While HER2-targeted agents are effective treatments, resistance remains a major cause of death. The American College of Surgeons Oncology Group Z1041 trial (NCT00513292) was designed to compare the pathologic complete response (pCR) rate of distinct regimens of neoadjuvant chemotherapy and trastuzumab, but ultimately identified no difference.

Patients and methods

In supplement to tissues from 37 Z1041 cases, 11 similarly treated cases were obtained from a single institution study (NCT00353483). We have extracted genomic DNA from both pre-treatment tumor biopsies and blood of these 48 cases, and performed whole genome (WGS) and exome sequencing. Coincident with these efforts, we have generated RNA-seq profiles from 42 of the tumor biopsies. Among patients in this cohort, 24 (50%) achieved a pCR.

Results

We have characterized the genomic landscape of HER2-positive breast cancer and investigated associations between genomic features and pCR. Cases assigned to the HER2-enriched subtype by RNA-seq analysis were more likely to achieve a pCR compared to the luminal, basal-like, or normal-like subtypes (19/27 versus 3/15; P = 0.0032). Mutational events led to the generation of putatively active neoantigens, but were overall not associated with pCR. ERBB2 and GRB7 were the genes most commonly observed in fusion events, and genomic copy number analysis of the ERBB2 locus indicated that cases with either no observable or low-level ERBB2 amplification were less likely to achieve a pCR (7/8 versus 17/40; P = 0.048). Moreover, among cases that achieved a pCR, tumors consistently expressed immune signatures that may contribute to therapeutic response.

Conclusion

The identification of these features suggests that it may be possible to predict, at the time of diagnosis, those HER2-positive breast cancer patients who will not respond to treatment with chemotherapy and trastuzumab.

ClinicalTrials.gov identifiers

NCT00513292, NCT00353483.

Abstract P4-12-04: Cost-effectiveness analysis of locally advanced estrogen receptor-positive, HER-2 negative breast cancer care using a tailored treatment approach in Brazil

Introduction: Breast cancer is the most common cancer in women worldwide, and 70% of breast cancer deaths occur in women from low-income and middle-income countries. In Brazil there were 14388 deaths due to this disease in 2013 and an estimate of over 58000 new cases in 2016. Neoadjuvant endocrine therapy (NET) is an attractive alternative to Neoadjuvant chemotherapy (NAC) for Hormone Receptor-positive tumors and could be a resources-saving strategy of treatment.

Methods: We built a decision analysis model of breast cancer treatment to compare a NET schema, with response based on the evaluation of Ki-67, against the surgery followed by adjuvant chemotherapy (AC) and radiation therapy (RT) standard-of-care as two competing approaches to breast cancer management. Our objective is to determine whether tailoring chemotherapy treatment based on response to neoadjuvant endocrine therapy is a cost-effective approach. The NET schema is based on the ACOSOG Z1031B trial, in which post-menopausal women with estrogen receptor-positive, HER-2 negative disease would receive 4 weeks of NET followed by a core-needle biopsy for Ki-67 evaluation. If Ki-67 were lower than 10%, patients would continue in NET for 16-18 weeks followed by surgery and RT according to international guidelines. The indication of AC in these patients would be based on the preoperative endocrine prognostic index (PEPI). Patients with a PEPI score equal to zero would be spared from AC. If Ki-67&gt;10%, patients would be triaged to NAC or surgery. The cost-effectiveness analysis was conducted using a Markov model from the provider's perspective, in this case the Brazilian Health ministry. Healthcare costs, in the form of charges from the hospitals to the health ministry, were obtained from cost tables available at the federal government's webpage. In the Markov model, possible health states were disease-free, local relapse, metastatic disease and death.Transition probabilities and mortality rates were extracted from randomized studies. Our assumptions were that both treatment strategies have similar clinical outcomes and that Ki-67 is a reliable method to triage patients to NAC or surgery. We performed one-way sensitivity analysis to assess the impact of the failure of the Ki-67 test on cost-effectiveness.

Results: Our model shows that the NET schema dominates the standard-of-care strategy. Costs were R$ 47799.89 per patient for the NET strategy and R$79809.24 for the standard-of-care strategy. There was an incremental cost saving of R$32009.36 per patient for the NET strategy compared to the standard-of-care strategy. Cost-effectiveness of the NET strategy was R$2612.63 and R$4369.11 for the standard-of-care. Considering the willingness-to-pay of R$ 85494.00, defined by the World Health Organization as three times the gross domestic product per capita, the standard-of-care strategy would only be more cost-effective in the scenario of a Ki-67 test that misclassifies patients more than 9.1% of the time.

Conclusion: The use of response to neoadjuvant endocrine treatment based on Ki-67 analysis as a way to tailor locally advanced breast cancer treatment is a cost-saving strategy in the presence of robust biomarkers.

Citation Format: Goncalves R, Reinert T, Ellis MJ, Sarian LO, Filassi JR. Cost-effectiveness analysis of locally advanced estrogen receptor-positive, HER-2 negative breast cancer care using a tailored treatment approach in Brazil [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P4-12-04.

Abstract GS2-01: Discovery and characterization of an estrogen bound LncRNA in late-Stage breast cancer

Breast cancer is the second most common newly diagnosed cancer and the second leading cause of cancer death among women in the United States. Despite the proven benefits of adjuvant endocrine therapy in women with hormone receptor positive breast cancer, relapses still occur over 5 years after initial treatment with endocrine therapy, referred to as late-stage relapse. Currently, the mechanisms of driving late-stage relapse are poorly characterized. To date, breast cancer research has primarily focused on protein-coding genes thereby missing the emerging class of long intergenic non-coding RNAs (lncRNAs) that may serve as critical regulators of relapse. Furthermore, the current understanding of lncRNA function is still in its infancy representing a critical gap for translating lncRNA discoveries into real-world applications to benefit patient care. Several well-described examples indicate that lncRNAs may be master epigenetic regulators in cancer biology through their interactions with proteins regulating target gene expression. Therefore, we hypothesize that lncRNAs may interact with estrogen receptor alpha 1 (ESR1) to regulate genes promoting late-stage relapse. To address this, we performed a transcriptome analysis of tumors from a unique cohort of 24 patients that had late-stage relapse to discover a novel set of lncRNAs, most of which have not yet been characterized. Next, we used RNA Immunoprecipitation coupled with transcriptome sequencing (RIP-Seq) to identify transcripts bound to ESR1 in T47D cells. We discovered 217 lncRNAs bound to ESR1 of which 50 were up-regulated in late-stage breast cancer. We chose to focus the most up-regulated lncRNA in late-stage relapse. Since it is an unannotated lncRNA we will refer to it as 'LAte-Stage relapse ESR1-Bound lncRNA 1', or LASER-1. To further understand the interplay between LASER-1 and ESR1, cells endogenously expressing LASER-1 were subjected to partial digestion to preserve lncRNA and protein interactions. Protected RNA fragments were subsequently immunoprecipitated with ESR1 and quantified by qPCR to reveal specific ESR1 interaction sites within LASER-1. Next, we observed increased expression of LASER-1 in ER+ breast cancer cell lines. Notably, LASER-1 expression was elevated in MCF7 long-term estrogen deprived (MCF7 LTED) cells -- that have amplified ESR1 -- relative to parental MCF7 cells. To demonstrate that LASER-1 promotes oncogenic phenotypes we transiently silenced LASER-1 in two cell lines with high endogenous expression of LASER-1 (including MCF LTED) and observed a decrease in cellular proliferation and invasion. Subsequent gene expression analysis after silencing LASER-1 altered mRNA and protein levels of critical cell cycle genes (i.e., p27). Overall, this is the first study to discover ESR1 bound lncRNAs that may be contributing to late-stage relapse in breast cancer. In the short-term, our ongoing research may lead to significant breakthroughs establishing the importance of LASER-1 as a master regulator in late-stage relapse. In the longer-term, we envision this research may lead to the development of novel therapeutics targeting LASER-1 with the potential for rapid clinical translation.

Citation Format: Maher CA, Silva-Fisher J, Eteleeb A, Tang C, Perou C, Reis-Filho JS, Mardis ER, Ellis MJ. Discovery and characterization of an estrogen bound LncRNA in late-Stage breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr GS2-01.

Abstract PD5-09: Fulvestrant for hormone receptor-positive advanced breast cancer in patients with visceral vs non-visceral metastases: Findings from FALCON, FIRST, and CONFIRM

BACKGROUND

Patients with hormone receptor-positive (HR+) locally advanced or metastatic breast cancer (LA/MBC) and non-visceral metastases (non-VM) generally have a better prognosis than patients with visceral metastases (VM). However, in the absence of visceral crisis, endocrine therapy (ET) remains an effective treatment option in both patient groups. This descriptive analysis examined the treatment effect of fulvestrant 500 mg vs comparators in postmenopausal patients with HR+ LA/MBC, with or without VM.

METHODS

Three randomized studies of fulvestrant 500 mg for postmenopausal HR+ LA/MBC were included. The Phase 3 FALCON study (NCT01602380) compared fulvestrant 500 mg with anastrozole in patients without any prior ET (n=462; fulvestrant 500 mg: 58.7% with VM; anastrozole: 51.3% with VM). The Phase 2 FIRST study (NCT00274469) compared fulvestrant 500 mg with anastrozole in patients who had not received ET for advanced disease (n=205; fulvestrant 500 mg: 47.1% with VM; anastrozole: 56.3% with VM). The Phase 3 CONFIRM study (NCT00099437) compared fulvestrant 500 mg with fulvestrant 250 mg (n=736; fulvestrant 500 mg: 56.6% with VM; fulvestrant 250 mg: 52.9% with VM); patients had received prior ET for adjuvant/advanced disease. The treatment effect of fulvestrant 500 mg vs comparator ET was determined using log-rank tests.

RESULTS

In FALCON, there was a greater treatment effect with fulvestrant 500 mg vs anastrozole for progression-free survival (PFS) in the non-VM group (hazard ratio [HR] 0.59) vs the VM group (HR 0.99). A consistent treatment effect was observed for fulvestrant 500 mg vs comparator for PFS in FIRST (non-VM HR 0.58; VM HR 0.82) and CONFIRM (non-VM HR 0.72; VM HR 0.86). Median PFS of fulvestrant 500 mg vs comparator in non-VM and VM subgroups was: 22.3 months (m) vs 13.8 m and 13.8 m vs 15.9 m, respectively, in FALCON; 34.0 m vs 21.3 m and 9.8 m vs 9.9 m in FIRST; and 10.4 m vs 5.9 m and 4.7 m vs 4.0 m in CONFIRM.

Clinical benefit rate with fulvestrant 500 mg vs anastrozole in FALCON was 87.4% vs 75.2% in the non-VM group, and 71.9% vs 73.1% in the VM group.

Overall survival (OS) in FALCON (31% maturity) showed a greater treatment effect with fulvestrant 500 mg vs anastrozole in the non-VM group vs the VM group (HR 0.60 vs 1.09). In terms of OS, in FIRST there was a greater treatment effect with fulvestrant 500 mg vs anastrozole in the non-VM group compared with the VM group (HR 0.68 vs 0.86). In CONFIRM, improved OS was observed with fulvestrant 500 mg vs fulvestrant 250 mg; this treatment effect was consistent in non-VM (HR 0.78) and VM subgroups (HR 0.83).

CONCLUSIONS

In three studies, an improved treatment effect of fulvestrant 500 mg vs comparator ET for HR+ LA/MBC was observed in patients with non-VM. The treatment effect of fulvestrant 500 mg vs comparator for PFS across all three studies appeared consistent. A reduced treatment effect of fulvestrant 500 mg vs comparator was generally seen in patients with VM, although fulvestrant 500 mg was still as effective as, or slightly more effective than, the comparator. These data suggest that patients without VM may benefit more from fulvestrant 500 mg than patients with VM.

Citation Format: Roberston JFR, Di Leo A, Fazal M, Lichfield J, Ellis MJ. Fulvestrant for hormone receptor-positive advanced breast cancer in patients with visceral vs non-visceral metastases: Findings from FALCON, FIRST, and CONFIRM [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr PD5-09.

Abstract P2-09-19: Genomic biomarker for resistance to palbociclib in the NeoPalAna trial

Background: Cyclin-dependent kinase (CDK) 4/6 inhibitors are being evaluated in the adjuvant setting for patients with resected early stage hormone receptor positive (HR+) and HER2 negative (HER2-) breast cancer (BC). However, biomarkers that predict benefit from this class of agents are unknown. We have recently reported results from the phase II neoadjuvant NeoPalAna trial which demonstrated that palbociclib (Pal) enhanced the anti-proliferative activity when added upon anastrozole (Ana) monotherapy in estrogen receptor (ER) positive and HER2 negative breast cancers. Interestingly, a small group of patients was resistant to Pal, exhibiting persistent tumor cell proliferation (Ki67 &gt;2.7%) on the combination of Ana and Pal. In this study, we evaluated the utility of a research algorithm for the 70-gene signature (70-GS) in identifying Pal resistant versus sensitive patients. Methods: Serial biopsies were collected from patients at four treatment timepoints: baseline (BL), cycle 1 day 1 (C1D1) following 28 days of Ana monotherapy, cycle 1 day 15 (C1D15) at 2 weeks post the addition of Pal, and at surgery (Surg). RNA was extracted from frozen tumor biopsies at each timepoint and run on Agilent full genome microarrays (GSE93204) at Washington University. As an exploratory analysis, genes from the GPL8253 array that match the 70-GS were used to calculate a research approximation of the 70-GS index (r-GS). The distribution of the r-GS across Ki67 response groups was evaluated. Results: Ki67 had previously been measured at each timepoint, and used to classify patients as being either Ana-sensitive (C1D1 Ki67 ≤2.7%), Pal-sensitive (C1D1 Ki67 &gt;2.7%, C1D15 Ki67 ≤2.7%), or Pal-resistant (C1D15 Ki67 &gt;2.7%). The r-GS was differentially regulated between sensitive (AI or Pal) and Pal-resistant groups at BL (p=0.012), C1D1 (p=0.039), and C1D15 (p=0.022). The r-GS values varied widely across patients at BL, and generally became more positive (more low risk) with treatment. There was no correlation between Ki67 levels and r-GS. Furthermore, gene expression analysis was performed to elucidate the difference between Pal-sensitive vs. Pal-resistant patients, and Ana-sensitive vs. Pal-sensitive patients. Conclusions: While on-treatment Ki67 indicated drug responsiveness, baseline r-GS significantly stratified patients into sensitive (Ana or Pal) versus Pal-resistant groups in the neoadjuvant setting. This preliminary finding suggests that the 70-GS may have clinical utility in identifying patients resistant to Pal for future studies. Additionally, results of the gene expression analysis may help to further develop genomic biomarkers for Pal and Ana sensitivity and resistance.

Citation Format: Hoog JW, Treece T, Blumencranz L, Audeh W, Sanati S, Ellis MJ, Ma CX. Genomic biomarker for resistance to palbociclib in the NeoPalAna trial [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P2-09-19.

Abstract P4-10-15: Impact of delay in breast cancer diagnosis and treatment according to health insurance status in southwest Brazil and Houston, Texas

Background: Access to medical care vary across the world and is related to different health systems with an impact in recurrence.Objective: To evaluate disparities in breast cancer(BC) diagnosis and treatment between public and private services in southwest Brazil and at two public safety net hospitals in Houston, Texas.Methods: Women diagnosed with BC stages I-III between 2009 to 2011, and treated at the four hospitals in Brazil and two health centers in US were included. All statistical analyses were performed in R studio software, and p&lt;0.05 was considered significant.Results: 1245 women were included: 967 from public health system (PHS) (20.3% from Houston, Texas) and 274 from private system(PS). Recurrence rate was higher in PHS (14.6% vs. 2.6%, p&lt;0.001)

Table 1. Clinical and demographic characteristics of the patientsCharacteristicsPublic (%), n=967Private (%), n=274pDiscovery of BC   By patient530 (54.8)92 (33.5) Routine exam87 (9)109 (39.8) Screening mammography270 (27.9)23 (8.4) Other80 (8.3)50 (18.3)&lt;0.001Initial treatment   Surgery687 (71)241 (88) Neo-adjuvant chemotherapy224 (23.2)27 (9.8) Neo-adjuvant hormone therapy23 (2.3)27 (9.8) Not available33 (3.4)3 (1.1)&lt;0.001Clinical Stage   I293 (30.3)113 (41.2) II342 (35.4)52 (19) III271 (28)15 (5.5) Unknown61 (6.3)94 (34.3)&lt;0.001Subtype   HR+/HER2 -561 (58)192 (70.1) HR-/HER2+108 (11.1)29 (10.6) HR-/HER2+76 (7.9)14 (5.1) Triple negative149 (15.4)28 (10.2) Unknown73 (7.6)11 (4)0.012Symptomatic at Diagnosis   Yes591 (61.1)100 (36.5) No306 (31.6)97 (35.4) Unknown70 (7.2)77 (28.1)&lt;0.001Recurencen=772n=146 No719 (74.4)193 (70.4) Yes142 (14.6)7 (2.6) Unknown106 (11)74 (27)&lt;0.001

. Considering the interval in weeks: symptoms to diagnosis, diagnosis to first treatment (either surgery or neoadjuvant chemotherapy), diagnosis to first systemic treatment, diagnosis to surgical treatment and diagnosis to radiotherapy were longer in public patients (24.1 vs. 8.7; 11.1 vs. 3.5; 18.6 vs. 9.8; 16.9 vs. 5.6; 51.4 vs. 26.1; p&lt;0.001).

Table 2. Delay disparities between public and private health system PublicPrivatepSymptoms to diagnosis   Number of patients575146 Time (weeks)24.1 (0.4-104.9)8.7 (0.0-43.7)&lt;0.001Diagnosis to first treatment   Number of patients663180 Time (weeks)11.1 (2.0-31.5)3.5 (0.0-11.0)&lt;0.001Diagnosis to first systemic treatment   Number of patients526106 Time (weeks)18.6 (2.6-44.7)9.8 (1.9-29.3)&lt;0.001Diagnosis to surgical treatment   Number of patients657178 Time (weeks)16.9 (3.4-45.6)5.6 (0.0-32.9)&lt;0.001Diagnosis to radiotherapy   Number of patients465127 Time (weeks)51.4 (18.7-88.4)26.1 (5.6-66.4)&lt;0.001

In multivariate analysis, PHS (HR 1.72; 95% CI 1.34-1.88; p adj=0.003), presence of symptoms (HR 2.29; 95% CI 1.39-3.78; p adj=0.001), clinical stage III (HR 1.62; 95% CI 1.35-1.93; p adj&lt;0.001), and triple negativity and HER2neu positivity (1.18; 95% CI 1.03-1.35; p adj=0.021) were all associated with a higher recurrence rate.Conclusions: There were significant disparities between PHS and PS. Women in the PHS presented higher rates of recurrence, advanced clinical stages at diagnosis, symptoms and more aggressive subtypes by IHC. additionally, the interval between symptoms to diagnosis and diagnosis to treatments was longer in PHS.

Citation Format: NematiShafaee M, Natal RA, Ramalho S, Dória MT, Conz L, Cabello V, Pavanello M, Mano MS, Linck RDM, Batista LS, Pedro EP, Bines J, de Paula BH, Zucca-Matthes G, Bondy ML, Ellis MJ, Podany E, Debord L, Makawita S, Stewart K, Cabello C. Impact of delay in breast cancer diagnosis and treatment according to health insurance status in southwest Brazil and Houston, Texas [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P4-10-15.

Abstract PD8-03: ESR1 gene fusions drive endocrine therapy resistance and metastasis in breast cancer

Background. Dysregulation of the estrogen receptor gene (ESR1) is an established mechanism of inducing endocrine therapy resistance. We previously discovered a chromosomal translocation event generating an estrogen receptor gene fused in-frame to C-terminal sequences of YAP1 (ESR1-YAP1) that contributed to endocrine therapy resistance in estrogen receptor positive (ER+) breast cancer models. This study compares functional, transcriptional, and pharmacological properties of additional ESR1 gene fusion events of both early stage (ESR1-NOP2) late stage (ESR1-YAP1 and ESR1-PCDH11x) breast cancers to gain a better understanding of therapeutic resistance and metastasis. Understanding the role of ESR1 fusions in inducing metastasis is critical, since the primary cause of death in breast cancer patients is through metastasis to distant sites.

Methods. RNA-seq screens identified ESR1 fusions from early and late stage, endocrine therapy resistant breast tumor samples. Functional experiments were conducted using ER+ breast cancer cell lines, xenograft, and PDX models to test the ability of ESR1 fusions to induce therapeutic resistance and metastasis. ChIP-seq and RNA-seq were performed to examine transcriptional properties and differential gene expression induced by the fusions which directed subsequent pharmacological experiments with a CDK4/6 inhibitor.

Results. ESR1-YAP1 and ESR1-PCDH11x promoted estrogen-independent and fulvestrant-resistant growth in vitro and induced greater tumor growth and increased metastatic capacity to the lungs of xenografted mice. In contrast, the ESR1-NOP2 fusion was sensitive to low estrogen conditions in vitro, and did not promote tumor growth. RNA-seq profiling revealed E2F targets pathway as the most highly enriched pathway induced by the ESR1 fusions. IHC revealed higher levels of pRb in ESR1-YAP1 and ESR1-PCDH11x xenograft tumors and subsequent CDK4/6 inhibition completely blocked tumor growth in an ESR1-YAP1 PDX model. Integrating RNA-seq with ChIP-seq data, we discovered a set of EMT and metastasis genes bound by all ESR1 fusions and WT-ER, but whose expression was strongly and uniquely up-regulated only by the ESR1-YAP1 and ESR1-PCDH11x fusions. These studies also revealed gained sites bound only by the ESR1-YAP1 and ESR1-PCDH11x fusions, not bound by WT-ER nor ESR1-NOP2. Genes mapping to these sites have a role in metastatic biology and were highly up-regulated by the YAP1 and PCDH11x fusions, potentially mediated by long range transcriptional activation.

Conclusion. ESR1-YAP1 and ESR1-PCDH11x are driver fusions that occur in drug-resistant, advanced stage breast cancer and are a new class of recurrent somatic mutation that can cause acquired endocrine therapy resistance, yet can be treated with CDK4/6 inhibition. These driver fusions also confer increased metastatic ability through their ability to drive expression of genes that contribute to EMT and metastasis. In contrast, ESR1-NOP2 did not produce functional protein and appears to be a passenger event. These studies may provide pre-clinical rationale for targeting ESR1 translocated breast tumors, since the presence of an ESR1 driver fusion places a patient in a therapeutic category where none of the currently available endocrine therapies are likely to be effective.

Citation Format: Lei JT, Shao J, Zhang J, Iglesia M, Chan DW, Cao J, Anurag M, Singh P, Haricharan S, Kavuri SM, Matsunuma R, Schmidt C, Kosaka Y, Crowder R, Hoog J, Phommaly C, Goncalves R, Ramalho S, Rodrigues-Peres RM, Lai W-C, Hampton O, Rogers A, Tobias E, Parikh P, Davies S, Ma C, Suman V, Hunt K, Watson M, Hoadley KA, Thompson A, Perou CM, Creighton CJ, Maher C, Ellis MJ. ESR1 gene fusions drive endocrine therapy resistance and metastasis in breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr PD8-03.

Abstract P5-06-01: Proteomic analysis of conserved kinases between PDX tumors and corresponding PDX-derived cell lines

(Background) Patient-derived xenograft (PDX)s are valuable models for precision oncology as they are thought to recapitulate the biological and genomic characteristics of the human tumors they were derived from. Even though this model is widely used, it is still difficult to manipulate genes in this system and it is not as convenient as in vitro cell culture for drug sensitivity screening. On the other hand in vitro cell cultures have a highly artificial microenvironment and also have undergone selection which might generate misleading data. To address these issues cell lines from PDX tumors with different intrinsic subtypes were characterized by kinobead precipitation/mass spectrometry analysis (KiP/MS) to profile each PDX line in vivo and ex vivo for therapeutic targets.

(Materials and Methods)Washington University Human in Mice (WHIM) tumors and Hutsman Cancer Institute (HCI) tumors were transplanted into mammary fat pads of female severe combined immunodeficiency/beige (SCID/beige) mice. PDXs tumors were harvested when they reached 1˜1.5cm. PDX tumor-derived ex vivo cells/organoids were routinely cultured with Rock inhibitor support. Estradiol was applied only for the tumors originating from E2 supplementation in vivo. Cells and tumors were harvested and lysed by sonication. Kinases in soluble lysates are enriched with drug-bound beads (kinobead) and digested with trypsin. Digested peptides are analyzed by mass spectrometry.

(Results) 5 of WHIM tumors and 4 of HCI tumors were successfully dissociated and cultured ex vivo for further analysis and experiments. Hierarchical clustering of tumors and corresponding cells showed ex vivo cultured cells cluster together with their original PDX tumors. Tumors/ex vivo cultured cells clustered by intrinsic subtype and enrichment analysis identified specific kinases for each PDX tumor/cell line. The WHIM 4 tumor-cell pair showed high level of PIM kinase and EGFR and other PDX tumors such as WHIM18, WHIM 20 (Luminal subtypes), WHIM 35(HER2 enriched subtype) also showed model unique intrinsic kinases, such as JAK2 for WHIM18, EPHB4 for WHIM20.

(Conclusion) PDX tumor-derived ex vivo lines could be routinely cultured with Rock inhibitor support. Each PDX tumor and cell line pair were cluster together in hierarchical clustering and categorized into the same intrinsic subtype based on kinome profiling, suggesting these cells maintain their tumor specific intrinsic kinase signaling. A subset of kinases exhibit activity/expression that is conserved after ex vivo culture, we hypothesize these are intrinsic kinases might be promising target for treatment, because they are tumor intrinsic, i.e. their high expression is maintained despite the strong contrast in the microenvironment of in vitro versus in vitro growth. Ongoing studies with drugs and knock down reagents are examining whether the in vivo/ex vivo comparative KIP analysis indeed identifies therapeutic targets, which will be presented at the meeting more in detail.

Citation Format: Han A, Kim B-J, Chan DW, Matsunuma R, Singh P, Ellis MJ. Proteomic analysis of conserved kinases between PDX tumors and corresponding PDX-derived cell lines [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P5-06-01.

Seven-year (yr) follow-up of adjuvant paclitaxel (T) and trastuzumab (H) (APT trial) for node-negative, HER2-positive breast cancer (BC)

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Background: Retrospective data suggest that patients (pts) with small HER2+ cancers have more than just minimal risk of disease recurrence. The APT trial was designed to address treatment for such pts. We have previously reported 3-yr disease-free survival (DFS) and here we provide an updated analysis with 7-yr DFS. Methods: APT is a single arm multicenter, phase II study of TH. Pts with HER2+ BC (IHC 3+ and/or FISH ratio > 2.0) with negative nodes (a single axillary lymph node micrometastasis was allowed) and tumor size < 3 cm were eligible. Pts received T (80 mg/m2) with H x 12 weekly (w), followed by H (weekly or q3w) x 39w. The primary endpoint was DFS. Recurrence Free Interval (RFI), Breast Cancer Specific Survival (BCSS), and overall survival (OS) were also analyzed. Intrinsic subtyping by PAM50 was performed on the nCounter Analysis system on archival tissue. Results: 410 pts were enrolled from September 2007 to September 2010 and 406 began protocol therapy. 67% had hormone-receptor (HR)+ tumors. Distribution by tumor size: 2% T1mi; 17% T1a; 30% T1b; 42% T1c, and 9% T2 ≤ 3 cm. 6 pts had a nodal micrometastasis. With a median follow-up of 6.5 yrs, there were 23 DFS events observed: 4 (1.0%) distant recurrences, 5 local/regional recurrences (1.2%), 6 new contralateral BC (1.5%), and 8 deaths without documented recurrence (2.0%). The 7-yr DFS was 93.3% (95% CI 90.4-96.2); 7-yr DFS for HR+ pts was 94.6% (95% CI 91.8-97.5) and for HR- pts was 90.7% (95% CI 84.6-97.2). 7-yr RFI was 97.5% (95% CI 95.9-99.1); 7-year BCSS is 98.6% (95% CI 97.0-100); and 7-yr OS was 95.0% (95% CI 92.4-97.7). Ongoing PAM50 testing (n = 227 pts) identified 142 (63%) HER2-enriched; 22 (10%) luminal A, 26 (11%) luminal B, and 20 (9%) basal-like; 17 samples had a poor quality assay. Additional testing and associations with clinical outcomes will be presented at the meeting. Conclusions: These data suggest that TH as adjuvant therapy for node-negative HER2+ BC is associated with few recurrences and only 4 distant recurrences with longer follow-up. Based on these data, if chemotherapy/trastuzumab is given to a pt with stage I HER2+ breast cancer, the TH regimen should be considered a standard treatment. Clinical trial information: NCT00542451.

Abstract PD2-03: Recurrent functionally diverse in-frame ESR1 gene fusions drive endocrine resistance in breast cancer

Background. We previously reported an alternative ESR1 somatic gain-of-function chromosomal translocation event in a patient presenting with aggressive, endocrine therapy resistant estrogen receptor (ER) positive disease, producing an in-frame fusion gene consisting of N-terminal ESR1 and the C-terminus of the Hippo pathway coactivator YAP1 (ESR1-YAP1). We recently identified another ESR1 fusion through RNA sequencing (RNA-seq) in advanced stage ER+ disease from a chest wall recurrence in a male patient that was refractory to multiple lines of treatment. Two examples of fusions discovered in primary breast cancer samples include ESR1 fused in-frame to C-terminal sequences from NOP2 (ESR1-NOP2), identified in a resistant cohort from a RNA-seq screen focused on 81 primary breast cancers from aromatase inhibitor clinical trials, and a second ESR1 fusion, fused in-frame to the entire coding sequence of POLH (ESR1-POLH), that was identified from RNA-seq analysis of 728 Cancer Genome Atlas breast samples. This current study extends our previous characterization of ESR1-YAP1 by comparing functional and pharmacological properties of these three additional ESR1 gene fusion events of both early stage and advanced breast cancers.

Methods. In vitro and in vivo experiments were conducted to test ESR1 fusions to induce therapeutic resistance, and metastasis. The transcriptional and binding properties of each fusion was also examined. Pharmacological inhibition with Palbociclib, a cyclin-dependent kinase 4/6 inhibitor, was utilized to assess drug sensitivity in ESR1 fusion containing breast cancer cells and in a patient derived xenograft (PDX) model expressing ESR1-YAP1 (WHIM18).

Results. The YAP1 and PCDH11x fusions conferred estrogen-independent and fulvestrant-resistant growth. Immunohistochemistry revealed significantly higher numbers of ER+ cells in lungs of mice xenografted with T47D cells expressing the YAP1 and PCDH11x fusions compared to YFP control, NOP2 and POLH fusions. Results from ChIP-seq and microarray studies suggest that these two fusions promote proliferation and metastasis through genomic action by binding estrogen response elements (ERE) and subsequent gene activation. We thereby define these fusions as “canonical” fusions compared to “non-canonical” NOP2 and POLH fusions, which demonstrated dramatically decreased genomic binding ability. The non-canonical fusions induced genes associated with basal-like breast cancer and promoted HER2, EGFR, and MAPK gene expression signatures in contrast to genes associated with cell cycle/proliferation induced by canonical fusions. The proliferative ability of canonical fusion-containing ER+ cells was inhibited by Palbociclib in a dose-dependent manner. In vivo WHIM18 tumors in mice fed with Palbociclib-containing chow demonstrated significantly reduced tumor volume, growth rate, and weight compared to tumors in mice on control chow.

Conclusions. In-frame ERE activating canonical fusions occur in end-stage drug resistant advanced breast cancer and can be added to ESR1 point mutations as a class of recurrent somatic mutation that may cause acquired resistance. Growth induced by these fusions can be antagonized by Palbociclib and is potentially clinically helpful.

Citation Format: Lei JT, Shao J, Zhang J, Iglesia M, Cao J, Chan DW, He X, Kosaka Y, Schmidt C, Matsunuma R, Haricharan S, Crowder R, Hoog J, Phommaly C, Goncalves R, Ramalho S, Lai W-C, Hampton O, Rogers A, Tobias E, Parikh P, Davies S, Ma C, Suman V, Hunt K, Watson M, Hoadley KA, Thompson A, Chen X, Perou CM, Creighton CJ, Maher C, Ellis MJ. Recurrent functionally diverse in-frame ESR1 gene fusions drive endocrine resistance in breast cancer [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr PD2-03.

Abstract P2-08-09: Progression-free survival results in postmenopausal Asian women: Subgroup analysis from a phase 3 randomized trial of fulvestrant 500 mg vs anastrozole for hormone receptor-positive advanced breast cancer (FALCON)

BACKGROUND

Fulvestrant is a selective estrogen receptor degrader (SERD) with no known agonist effects. In the open-label Phase 2 FIRST study, fulvestrant 500 mg suggested improved efficacy as first-line treatment vs anastrozole in patients with hormone receptor-positive locally advanced or metastatic breast cancer (LA/MBC). The Phase 3, randomized, double-blind, multicenter FALCON trial (NCT01602380) compared fulvestrant 500 mg with anastrozole 1 mg in patients with hormone receptor-positive LA/MBC who had not received prior hormonal therapy. The primary endpoint of the study, progression-free survival (PFS) assessed via RECIST 1.1, surgery/radiotherapy for disease worsening, or death (any cause), was met, as shown by a statistically significant improvement in PFS for fulvestrant 500 mg vs anastrozole. This analysis evaluated PFS in the Asian patient subgroup, which included all randomized patients from centers in China, Japan, and Taiwan.

METHODS

Eligible patients had ER and/or progesterone receptor-positive breast cancer, WHO performance status 0–2, and ≥1 measurable/non-measurable lesion(s). Patients were randomized (1:1) to receive fulvestrant 500 mg (IM on Days 0, 14, 28, and each 28 days thereafter) or anastrozole 1 mg daily, and were stratified according to LA or MBC; prior or no prior treatment with chemotherapy for LA/MBC; and measurable or non-measurable disease. The consistency of effect across patient subgroups was assessed via hazard ratios and 95% confidence intervals using a log-rank test.

RESULTS

In total, 462 patients were randomized (n=230 fulvestrant 500 mg; n=232 anastrozole). The Asian subgroup comprised 67 patients (n=34 fulvestrant 500 mg; n=33 anastrozole). PFS outcomes for the Asian and non-Asian subgroups are presented (Table). The most commonly reported adverse event (AE) was arthralgia (18.2% vs 12.1% of patients with fulvestrant 500 mg and anastrozole, respectively). The rate of AEs leading to discontinuation of treatment was 3.0% and 3.0%, respectively.

CONCLUSIONS

Based on a preliminary assessment of 67 patients, the treatment effect in the Asian patient subgroup from the FALCON trial appears to be broadly consistent with the non-Asian population.

PFS in Asian and non-Asian patient subgroupsGeographic regionNumber of patients (%) with event Hazard ratio (95% CI) Fulvestrant 500 mg n=230Anastrozole n=232 Asia19/34 (55.9%)22/33 (66.7%)0.81 (0.44, 1.50)Non-Asia124/196 (63.3%)144/199 (72.4%)0.79 (0.62, 1.01)

Citation Format: Shao Z, Ellis MJ, Robertson JFR, Grinsted LM, Fazal M, Noguchi S. Progression-free survival results in postmenopausal Asian women: Subgroup analysis from a phase 3 randomized trial of fulvestrant 500 mg vs anastrozole for hormone receptor-positive advanced breast cancer (FALCON) [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P2-08-09.

Abstract P2-08-02: Progression-free survival results in patient subgroups from a Phase 3 randomized trial of fulvestrant 500 mg vs anastrozole for hormone receptor-positive advanced breast cancer (FALCON)

BACKGROUND

Improved efficacy was suggested for fulvestrant 500 mg, a selective estrogen receptor degrader (SERD), vs anastrozole as first-line treatment for hormone receptor-positive locally advanced or metastatic breast cancer (LA/MBC) in the open-label Phase 2 FIRST trial. The Phase 3, randomized, double-blind, multicenter FALCON trial (NCT01602380) compared fulvestrant 500 mg with anastrozole 1 mg in patients with hormone receptor-positive LA/MBC who had not received prior hormonal therapy. The primary endpoint of the study was met, such that there was a statistically significant improvement in progression-free survival (PFS) for fulvestrant 500 mg vs anastrozole. We present an analysis of PFS for pre-specified patient subgroups in the FALCON trial.

METHODS

Eligible patients had ER and/or progesterone receptor (PgR)-positive breast cancer, WHO performance status 0–2 and ≥1 measurable/non-measurable lesion(s). Patients were randomized (1:1) to receive fulvestrant 500 mg (IM on Days 0, 14, 28, and each 28 days thereafter) or anastrozole 1 mg daily. The primary endpoint was PFS, assessed via RECIST 1.1, surgery/radiotherapy for disease worsening, or death (any cause). PFS was evaluated in patient subgroups defined by pre-specified baseline covariates. The consistency of effect across patient subgroups was assessed via hazard ratios and 95% confidence intervals using a log-rank test.

RESULTS

Overall, 462 patients were randomized to treatment: 230 received fulvestrant 500 mg and 232 received anastrozole. PFS outcomes in each patient subgroup are presented in the Table.

CONCLUSIONS

This analysis of patient subgroups from the FALCON trial suggests that treatment effects were largely consistent across the subgroups analyzed with some possible exceptions (e.g. patients with visceral vs non-visceral disease). Further work is ongoing to understand the possible treatment effect in these subgroups.

PFS in pre-specified patient subgroupsSubgroup Number of patients (%) with event Hazard ratio (95% CI)  Fulvestrant 500 mg n=230 Anastrozole n=232 Breast cancer type   Locally advanced11/28 (39.3%)14/32 (43.8%)0.79 (0.36, 1.73)Metastatic132/202 (65.3%)152/200 (76.0%)0.78 (0.62, 0.99)Prior chemotherapy for LA/MBC   Yes31/36 (86.1%)33/43 (76.7%)1.08 (0.66, 1.77)No112/194 (57.7%)133/189 (70.4%)0.75 (0.59, 0.97)Geographic regiona   US/Canada16/25 (64.0%)19/24 (79.2%)0.66 (0.34, 1.30)Non-US/Canada127/205 (62.0%)147/208 (70.7%)0.81 (0.64, 1.03)Measurable disease   Yes124/193 (64.2%)143/196 (73.0%)0.76 (0.60, 0.97)No19/37 (51.4%)23/36 (63.9%)0.99 (0.53, 1.82)ER-positive and PgR-positive   Yes103/175 (58.9%)127/179 (70.9%)0.73 (0.56, 0.94)No40/55 (72.7%)39/53 (73.6%)1.04 (0.67, 1.62)Bisphosphonate use at baseline   Yes44/61 (72.1%)53/62 (85.5%)0.69 (0.46, 1.03)No99/169 (58.6%)113/170 (66.5%)0.82 (0.63, 1.07)Visceral disease   Yes92/135 (68.1%)87/119 (73.1%)0.99 (0.74, 1.33)No51/95 (53.7%)79/113 (69.9%)0.59 (0.42, 0.84)ªData for Asia/non-Asia subgroups are presented in a separate abstract

Citation Format: Robertson JFR, Noguchi S, Shao Z, Grinsted LM, Fazal M, Ellis MJ. Progression-free survival results in patient subgroups from a Phase 3 randomized trial of fulvestrant 500 mg vs anastrozole for hormone receptor-positive advanced breast cancer (FALCON) [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P2-08-02.

Abstract P1-08-01: Regulation of estrogen receptor-α by NF1

Background. Although great strides have been made in targeting the ER pathway for treating ER+ breast cancer, relapse and death is common and is closely linked to resistance to ER-targeting agents. As a result, the majority of deaths from breast cancer still come from ER+ tumors. To discover drivers for endocrine resistance, we have sequenced tumor DNAs from a cohort of &gt;600 patients treated with 5-year tamoxifen (Tam) monotherapy with a median 10.4 years follow up. Our preliminary data show that the worst outcome mutations (Hazard Ratio of ∼3 for relapse) were mostly those of the Neurofibromatosis type 1 (NF1) gene (encoding Neurofibromin), with nonsense/frame shift mutations creating early stop codons.

Germline NF1mutations cause neurofibromatosis type 1, a common inherited disorder that predisposes individuals to both benign and malignant tumors of the nervous system, as well as an increased risk for breast cancer. Analysis of DNA sequencing data has also shown that the NF1 gene is mutated in a wide range of common cancers (e.g., melanoma, lymphoma, and cancers of the lung, breast, and colon). Thus, NF1-deficiency underlies the formation and/or progression of a large number of cancers, so that the development of therapies targeted to NF1-deficient malignancies would have broad impact.

These observations support the hypothesis that NF1 gene inactivation is associated with aggressive tumor behaviors, such as endocrine therapy resistance in breast cancer. The key focus of this study is to define how the NF1 protein neurofibromin, regulates endocrine therapy resistance. Although neurofibromin is best known as a negative regulator for Ras, our data show that it may have other functions.

Method. Our data suggest that many of the identified nonsense/frame shift create a NF1 null state; thus, we have used gene-silencing to recapitulate the effects of such NF1 mutations on the activities of ER+ breast cancer cells. NF1+ and NF1– ER+ breast cancer cells were grown in defined media to measure how estradiol (E2) and Tam impact their growth, transforming activities, and gene expression. The binding between neurofibromin and components of the ER transcriptional pathway was measured biochemically and using the mammalian two-hybrid system.

Results. Our data showed that NF1-silenced cells use Tam as an agonist and can grow with very little E2, and these activities are driven by enhanced recruitment of ER to the ERE, leading to efficient expression of many classic ER-responsive genes. Expressing the NF1-GAP domain does not restore normal responses to Tam and E2 in NF1-silenced cells, suggesting that neurofibromincan regulate ER activity in a Ras-independent manner. To investigate the possibility that neurofibromin can directly regulate ER, we found that it can bind ER; furthermore, neurofibromin was more strongly recruited to the ERE by Tam than by E2.

Conclusion. Our data support a model whereby neurofibromin acts like a co-repressor for ER. As such,NF1 loss may result in more aggressive tumor behaviors by activating, not only the Ras pathways, but also the ER transcriptional pathways. Simultaneous activation of two powerful oncogenic pathways by the loss of a single tumor suppressor may explain why neurofibromin is such a potent tumor suppressor lost in a wide range of cancers.

Citation Format: Zheng Z-Y, Cakar B, Lavere P, Cao J, Yao J, Singh P, Lei JT, Toonen JA, Haricharan S, Anurag M, Shah K, Kavuri M, Chan DW, Chen X, Gutmann DH, Foulds CE, Ellis MJ, Chang EC. Regulation of estrogen receptor-α by NF1 [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P1-08-01.

Abstract P1-07-11: Tumor genomic profiling of triple negative breast cancer during neoadjuvant chemotherapy: Results from a prospective trial of carboplatin and docetaxel

Background-The clonal evolution and effect of neoadjuvant chemotherapy on the mutational landscape of triple negative breast cancer (TNBC) is unknown. Inability to eradicate TNBC may be due to clonal progression and selection of cells fundamentally resistant to chemotherapy.In this study, we sought to decipher the genomic architecture of TNBC serially during neoadjuvant chemotherapy to distinguish pre- versus post-chemotherapy genotypes.

Methods-Tumor specimens were obtained from patients with stages II and III TNBC enrolled on an ongoing prospective neoadjuvant co-clinical trial (NCT02124902). Patients have a research biopsy at baseline, cycle 1 day 3 (optional), and at definitive surgery for those with residual disease. Patients are treated with docetaxel 75mg/m2 and carboplatin AUC6 cycled every 3 weeks X six cycles. Definitive surgery is 3-5 weeks after chemotherapy. The primary endpoint is pathologic complete response rate. Correlative studies include development of patient derived xenografts, evaluation of genomic signatures of resistance and response, and comparison of chemotherapy responses between xenografts and host patients. Five patients' serial tumor samples and germline DNA were studied by exome and transcriptome sequencing. Three of these patients had an additional on-treatment sample at cycle 1 day 3. Two patients lacked residual disease samples- one was not banked and the other could not be accurately genotyped due to low cellularity. The median sequencing depth was 90.13x. Sequencing was performed on either fresh frozen or formalin-fixed paraffin-embedded samples with high cellularity (≥50%). After identifying somatic mutations in each tumor series, we evaluated whether each mutation was persistent, emergent, or cleared by comparing pre- and post-treatment (and when possible, on-treatment) samples.

Results-All five patients had response to neoadjuvant chemotherapy based on caliper-based and pathologic (residual cancer burden I or II) measurements. All residual disease remained TNBC by standard immunohistochemistry and all samples were basal-like from PAM50 gene expression analysis. We identified 908 somatic mutations, including the expected variants in TP53 which persisted in all post-treatment samples. Non-silent somatic variants were identified in other breast cancer-related genes, including GATA1, FBXO11, PIK3R1, AXIN2, ARID1B, BRCA2, and RBCC1. In spite of the clinico-pathologic evidence of response, we observed little change in clonal architecture, as derived from the purity-corrected variant allele fractions between baseline, cycle 1 day 3, and post-chemotherapy samples. Copy number alterations were likewise stable and transcriptional-based assessment indicated that patterns of mutant allele expression in driver genes were retained throughout the course of treatment.

Conclusion-In TNBC patients undergoing neoadjuvant platinum-based chemotherapy, there were no apparent shifts in the prevalence of known breast cancer specific somatic variants during or after chemotherapy. Despite pathologic response, core genomic features appear to be preserved in TNBC patients with residual disease following chemotherapy, likely accounting for high rates of relapse in these patients.

Citation Format: Ademuyiwa FO, Miller CA, Li T, Sanati S, Ma CX, Weilbaecher K, Ellis MJ, Mardis ER. Tumor genomic profiling of triple negative breast cancer during neoadjuvant chemotherapy: Results from a prospective trial of carboplatin and docetaxel [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P1-07-11.

The Z-cad dual fluorescent sensor detects dynamic changes between the epithelial and mesenchymal cellular states

BACKGROUND

The epithelial to mesenchymal transition (EMT) has been implicated in metastasis and therapy resistance of carcinomas and can endow cancer cells with cancer stem cell (CSC) properties. The ability to detect cancer cells that are undergoing or have completed EMT has typically relied on the expression of cell surface antigens that correlate with an EMT/CSC phenotype. Alternatively these cells may be permanently marked through Cre-mediated recombination or through immunostaining of fixed cells. The EMT process is dynamic, and these existing methods cannot reveal such changes within live cells. The development of fluorescent sensors that mirror the dynamic EMT state by following the expression of bona fide EMT regulators in live cells would provide a valuable new tool for characterizing EMT. In addition, these sensors will allow direct observation of cellular plasticity with respect to the epithelial/mesenchymal state to enable more effective studies of EMT in cancer and development.

RESULTS

We generated a lentiviral-based, dual fluorescent reporter system, designated as the Z-cad dual sensor, comprising destabilized green fluorescent protein containing the ZEB1 3' UTR and red fluorescent protein driven by the E-cadherin (CDH1) promoter. Using this sensor, we robustly detected EMT and mesenchymal to epithelial transition (MET) in breast cancer cells by flow cytometry and fluorescence microscopy. Importantly, we observed dynamic changes in cellular populations undergoing MET. Additionally, we used the Z-cad sensor to identify and isolate minor subpopulations of cells displaying mesenchymal properties within a population comprising predominately epithelial-like cells. The Z-cad dual sensor identified cells with CSC-like properties more effectively than either the ZEB1 3' UTR or E-cadherin sensor alone.

CONCLUSIONS

The Z-cad dual sensor effectively reports the activities of two factors critical in determining the epithelial/mesenchymal state of carcinoma cells. The ability of this stably integrating dual sensor system to detect dynamic fluctuations between these two states through live cell imaging offers a significant improvement over existing methods and helps facilitate the study of EMT/MET plasticity in response to different stimuli and in cancer pathogenesis. Finally, the versatile Z-cad sensor can be adapted to a variety of in vitro or in vivo systems to elucidate whether EMT/MET contributes to normal and disease phenotypes.

Abstract S6-05: A phase II trial of neoadjuvant palbociclib, a cyclin-dependent kinase (CDK) 4/6 inhibitor, in combination with anastrozole for clinical stage 2 or 3 estrogen receptor positive HER2 negative (ER+HER2-) breast cancer (BC)

Background

ER+ BC is associated with activated CDK4/6. The CDK4/6 inhibitor palbociclib (P) markedly improves time to progression in advanced ER+HER2- BC. We conducted a neoadjuvant phase II trial to determine the activity of P in primary breast cancer as a prelude to adjuvant studies.

Methods

To assess molecular changes induced by anastrozole (A) or P+A, patients (pts) were treated initially with A alone (1mg PO daily) for 28 days in cycle 0 (C0) before the addition of P (125mg PO daily on D1-21 each cycle) on C1D1. P+A was administered for 4 28-day cycles followed by C5 with A alone for 2-4 weeks (wks) before surgery. P was added in C5 for 10-12 days immediately prior to surgery in the last 20 pts enrolled to assess molecular changes induced by A, either alone or in combination with P immediately prior to surgery, in resected tumor. Goserelin was added in premenopausal pts.

Research tumor biopsies were obtained at baseline, C1D1, and C1D15. Central Ki67 analysis was performed at all timepoints, those with Ki67 &gt;10% at C1D15 went off study treatment.

The primary endpoint was complete cell cycle arrest (CCA), defined as Ki67 &lt;2.7%, at C1D15. Patient stratification was based on PIK3CA mutation status with an initial focus on PIK3CA wild type (WT) disease. Pts with PIK3CA mutant (Mut) tumors enrolled to a separate cohort. A sample size of 33 pts in the PIK3CA WT cohort was chosen based on the Fleming's single-stage phase II design to test the hypothesis that P+A leads to &gt; 50% improvement over A in CCA rate on C1D15 biopsy (44% with A alone based on historical data, vs 66% with P+A, power = 0.8, alpha=0.05). The primary endpoint is met if &gt;20 pts achieved CCA in this cohort.

Correlative endpoints included assessment of markers of proliferation, apoptosis, senescence, Rb, gene expression microarray, intrinsic subtype, and next generation sequencing of 83-gene panels, which will be reported at the meeting.

Results

Between 4/23/2013 and 4/24/2015, 50 pts (33 PIK3CA WT, 11 PIK3CA Mut, 2 pending, 4 tissue quantity or quality not sufficient for sequencing (QNS)) were enrolled to the study. Median age was 57.5 (range: 34.1–79.6) years. Four pts, all with WT PIK3CA, went off study due to Ki67 &gt;10% on C1D15 biopsy, 26 pts completed treatment and surgery, 1 refused surgery, 3 withdrew study treatment in C1, and 16 continued to receive study drug (2 in C0, 3 in C1, 4 in C2, 5 in C3, 1 in C4, and 1 in C5). Among the 40 pts currently evaluable for the primary endpoint (C1D15 Ki67), CCA occurred in 34 (85%) pts, including 9 of 9 (100%) PIK3CA Mut, 22 of 28 (78.5%) WT, and 3 of 3 QNS pts. Preliminary analysis of available data indicated a significantly lower Ki67 value after 2 wks of P+A (C1D15) compared to that on A alone (C1D1) (p=0.034, n=18).

Conclusion

This study met the primary endpoint demonstrating that P+A is a highly effective anti-proliferative combination. The sequential biopsy design clearly demonstrated that P+A increased cell cycle control over A alone. P+A was effective regardless of PIK3CA mutation status and these results support the evaluation of this combination in the adjuvant setting for ER+HER2- BC.

Citation Format: Ma CX, Gao F, Northfelt D, Goetz M, Forero A, Naughton M, Ademuyiwa F, Suresh R, Anderson KS, Margenthaler J, Aft R, Hobday T, Moynihan T, Gillanders W, Cyr A, Eberlein TJ, Hieken T, Krontiras H, Hoog J, Han J, Guo Z, Vij K, Mardis E, Al-Kateb H, Sanati S, Ellis MJ. A phase II trial of neoadjuvant palbociclib, a cyclin-dependent kinase (CDK) 4/6 inhibitor, in combination with anastrozole for clinical stage 2 or 3 estrogen receptor positive HER2 negative (ER+HER2-) breast cancer (BC). [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr S6-05.

Abstract PD6-02: The genomics of response to neoadjuvant trastuzumab and chemotherapy in HER2-positive breast cancer – Results from the ACOSOG Z1041 (Alliance) trial

Support: Alliance U10CA180821; Alliance Statistical Center grant U10CA180882; ACOSOG grant U10CA76001

HER2 gene amplification and its corresponding overexpression are present in approximately 12% of invasive breast cancers. While HER2-targeted agents (e.g. trastuzumab, pertuzumab, and lapatinib) are effective treatments, resistance remains a major cause of death from HER2-positive breast cancer. Mechanisms of resistance are poorly understood. Without a molecular understanding of these mechanisms, therapeutic advances will be delayed. We have generated molecular profiles of primary HER2-positive breast cancers treated on a neoadjuvant clinical trial, and compared features associated with response to treatment.

The American College of Surgeons Oncology Group (ACOSOG) Z1041 trial in HER2-positive breast cancer was designed to compare the pathologic complete response (pCR) rate of a regimen of paclitaxel and trastuzumab, followed by trastuzumab administered with fluorouracil, epirubicin, and cyclophosphamide (FEC-75) to a regimen of FEC-75 alone followed by paclitaxel and trastuzumab. The trial identified no difference in pCR rates between the regimens (Buzdar et al., The Lancet Oncology 2013). In supplement to the tissues obtained from 37 of the patients enrolled in the Z1041 trial, an additional 11 cases were obtained from a single institution study (201101961) of patients treated with neoadjuvant trastuzumab that had pre-treatment core biopsies suitable for genomic studies.

We have extracted genomic DNA from both pretreatment tumor biopsies and blood samples of these 48 patients and performed whole genome (WGS) and exome sequencing. Coincident with these efforts, we have extracted high quality RNA from 42 of the 48 biopsies, and have processed RNA-seq profiles of the tumors. Among patients in this cohort, 24 (50%) achieved a pCR. Because no difference was observed between arms of the Z1041 trial, patients with or without a pCR were directly compared without adjusting for treatment regimen.

On average, each tumor and normal sample pair were sequenced to a depth of 49.4x and 32.5x by WGS respectively. In total, 15,027 candidate somatic variants were identified in known genes, including 11,606 missense, 860 nonsense, and 418 frameshift insertions or deletions. Preliminary results identified mutations in HER2 that were associated with the failure to achieve pCR in several cases. Furthermore, tumors assigned to the HER2-enriched subtype by RNA-seq analysis were more likely to achieve a pCR (19 compared to 8) than tumors with genomic features indicative of either the luminal or basal-like subtypes (3 compared to 12); a significant difference in the proportion of cases that achieve pCR (Fisher's exact test p-value = 0.0032). The identification of these features suggests that it may be possible to predict, at the time of diagnosis, those patients who will not respond to the current standard of care for HER2-positive breast cancer.

Citation Format: Lesurf R, Griffith O, Griffith M, Watson MA, Hoog J, Ellis MJ, Ota D, Suman VJ, Meric-Bernstam F, Leitch AM, Boughey JC, Unzeitig G, Buzdar AU, Hunt KK, Mardis ER. The genomics of response to neoadjuvant trastuzumab and chemotherapy in HER2-positive breast cancer – Results from the ACOSOG Z1041 (Alliance) trial. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr PD6-02.

Abstract P5-13-04: A phase II neoadjuvant trial of MK-2206, an AKT inhibitor, in combination with anastrozole for clinical stage 2 or 3 PIK3CA mutant estrogen receptor positive HER2 negative (ER+HER2-) breast cancer (BC)

Background

Activating mutations in PIK3CA occur in approximately 40% ER+BC. MK-2206 (M), a pan-AKT inhibitor, induced apoptosis of ER+ BC under estrogen deprivation in preclinical studies. We conducted this neoadjuvant trial to determine the pathologic complete response (pCR) rate of M plus anastrozole (A) for PIK3CA mutant (Mut) ER+ BC.

Methods

This single arm open label study of M+A used a 2-stage Simon phase II design (stage 1, n=16; stage 2, n=13, alpha=0.10, power=0.90) to test whether pCR rate &lt;1% (based on historical data with A alone), against the alternative that pCR rate ≥15% in PIK3CA Mut ER+ BC. At least 1 pCR in stage 1 was required to proceed to stage 2.

Eligible patients (pts) with clinical stage II or III ER+HER2- BC were pre-registered and proceeded to a research tumor biopsy for PIK3CA sequencing, followed by treatment with daily A monotherapy for 28 days (cycle 0). Pts with PIK3CA Mut BC were subsequently registered, underwent a second biopsy, and started M (150mg PO weekly) with daily A on cycle 1 day 1 (C1D1) for a maximum of four 28-day cycles followed by surgery. Goserelin was added for premenopausal pts. A tumor biopsy on C1D17, 17 days post the start of M, was performed. Those with C1D17 Ki67 &gt;10% discontinued study treatment. pCR was defined as no invasive cancer in the breast and the lymph nodes. Tumor specimens collected at all timepoints are being analyzed for markers of proliferation, apoptosis, and PI3K pathway activity, gene expression microarray, intrinsic subtypes, and next generation sequencing of 83 genes.

Results

Of the 51 pts pre-registered, 35 pts did not register due to no PIK3CA mutation (n=22), inadequate specimen for testing (n=6), physician/pt decision (n=7). The remaining 16 pts (median age: 58, range: 40-77 years) received combination therapy. Three pts did not complete 4 cycles due to C1D17 Ki67 &gt;10% (n=2) and intolerability (grade (Gr) 4 transaminase elevation in C1, n=1). Other severe toxicities possibly related to M included Gr 3 rash (25%) and pruritus (12.5%). Of the 13 pts completed study therapy and underwent surgery, all had residual disease in the breast and 7 also had positive nodes. Table 1 summarized changes in Ki67 during treatment.

ComparisonsnAbsolute changes in Ki67 median (range)Wilcoxon signed rank p-valueC1D1 relative to pre-registration11-17.0% (-49.8 to 4.1%)0.0020C1D17 relative to pre-registration14-16.4% (-51.4 to 4.1%)0.0004C1D17 relative to C1D112-1.5% (-18.6 to 15.8%)0.9697C1D1, biopsy post 28 days of A alone; C1D17 biopsy post 17 days on combination therapy

Although Ki67 levels post A monotherapy (C1D1) or M+A (C1D17) were significantly lower than that of pre-registration samples, Ki67 did not differ between C1D17 and C1D1 samples. Other correlative studies are ongoing and results will be presented.

Conclusion

Despite the small sample size, biomarker analysis on serial biopsy specimens demonstrated that M+A is unlikely to be more effective than A alone in PIK3CA Mut ER+ BC. This trial demonstrated the feasibility of genomic sequencing for pt selection and the value of a small, well-designed proof-of-principle neoadjuvant trial for the evaluation of targeted agents.

Citation Format: Ma CX, Suman VJ, Goetz M, Northfelt D, Burkard M, Ademuyiwa F, Naughton M, Margenthaler J, Aft R, Gray R, Tavaarwerk A, Wilke L, Haddad T, Moynihan T, Loprinzi C, Hieken T, Hoog J, Guo Z, Han J, Vij K, Mardis E, Sanati S, Al-Kateb H, Doyle L, Erlichman C, Ellis MJ. A phase II neoadjuvant trial of MK-2206, an AKT inhibitor, in combination with anastrozole for clinical stage 2 or 3 PIK3CA mutant estrogen receptor positive HER2 negative (ER+HER2-) breast cancer (BC). [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P5-13-04.

Predicting response and survival in chemotherapy-treated triple-negative breast cancer

BACKGROUND

In this study, we evaluated the ability of gene expression profiles to predict chemotherapy response and survival in triple-negative breast cancer (TNBC).

METHODS

Gene expression and clinical-pathological data were evaluated in five independent cohorts, including three randomised clinical trials for a total of 1055 patients with TNBC, basal-like disease (BLBC) or both. Previously defined intrinsic molecular subtype and a proliferation signature were determined and tested. Each signature was tested using multivariable logistic regression models (for pCR (pathological complete response)) and Cox models (for survival). Within TNBC, interactions between each signature and the basal-like subtype (vs other subtypes) for predicting either pCR or survival were investigated.

RESULTS

Within TNBC, all intrinsic subtypes were identified but BLBC predominated (55-81%). Significant associations between genomic signatures and response and survival after chemotherapy were only identified within BLBC and not within TNBC as a whole. In particular, high expression of a previously identified proliferation signature, or low expression of the luminal A signature, was found independently associated with pCR and improved survival following chemotherapy across different cohorts. Significant interaction tests were only obtained between each signature and the BLBC subtype for prediction of chemotherapy response or survival.

CONCLUSIONS

The proliferation signature predicts response and improved survival after chemotherapy, but only within BLBC. This highlights the clinical implications of TNBC heterogeneity, and suggests that future clinical trials focused on this phenotypic subtype should consider stratifying patients as having BLBC or not.

Body mass index, diabetes, and triple-negative breast cancer prognosis

Higher body mass index (BMI) and diabetes are associated with worse breast cancer prognosis. However, few studies have focused on triple-negative breast cancer (TNBC). The goal of this study is to examine this association in a cohort of patients with TNBC. We retrospectively reviewed 501 consecutive patients with TNBC seen at the Washington University Breast Oncology Clinic. Cox proportional hazard models were used to determine the relationship between BMI and diabetes at diagnosis with overall survival (OS) and disease free survival (DFS). Four hundred and forty-eight patients had BMI recorded and 71 patients had diabetes. The median age at diagnosis was 53 (23-98) years and follow-up was 40.1 months (IQR 25.2-62.9). Baseline BMI and diabetes were not associated with OS or DFS. OS hazard ratios (HRs) for patients who were overweight (BMI 25.0-29.99), with class I obesity (BMI 30-34.99), or BMI ≥35 were 1.22 (CI 0.78-1.91), 0.92 (CI 0.59-1.43), and 1.16 (CI 0.70-1.90), respectively. The HRs for DFS in patients who were overweight, with class I obesity, or BMI ≥35 were 1.01 (CI 0.65-1.56), 0.94 (CI 0.60-1.47), and 0.99 (CI 0.63-1.57), respectively. Similarly, the HRs for diabetics were 1.27 (CI 0.82-1.96) for OS and 0.98 (CI 0.64-1.51) for DFS. Obesity and diabetes did not significantly affect survival for patients with TNBC in this study.

Abstract OT3-2-09: FALCON: A randomised, double-blind, multicentre, phase III study comparing fulvestrant 500 mg with anastrozole 1 mg for postmenopausal women with hormone receptor-positive locally advanced or metastatic breast cancer who have not previously been treated with any hormonal therapy

Background: The Phase III CONFIRM study demonstrated that a higher dose (500 mg) of fulvestrant, an estrogen receptor (ER) antagonist for treatment of advanced breast cancer, was associated with a significant increase in progression-free survival (PFS) without increased toxicity versus fulvestrant 250 mg.Moreover, a Phase II study (FIRST) showed that first-line treatment with fulvestrant 500 mg was at least as effective as anastrozole 1 mg with a similar safety profile. The aim of the FALCON study is to investigate whether fulvestrant 500 mg is superior to anastrozole 1 mg as first-line endocrine therapy. FALCON is the only Phase III study in recent years to compare two endocrine therapies as first-line treatment in metastatic breast cancer (MBC); hence, results may potentially affect standard clinical practice in the future.

Trial design: This is a randomised, double-blind, double-dummy, international, multicentre study comparing efficacy and tolerability of fulvestrant with anastrozole (NCT01602380). Eligible patients are randomised 1:1 to receive fulvestrant 500 mg or anastrozole 1 mg, and stratified at randomisation based on whether (1) they have locally advanced or MBC (2) they have received prior chemotherapy for locally advanced or MBC or not and (3) they have measurable or non-measurable disease.

Eligibility criteria: Eligible are postmenopausal women with histologically confirmed, ER-positive, locally advanced or MBC who have not previously received any endocrine therapy. Patients may have received one line of cytotoxic chemotherapy but must show progressive disease prior to enrolment, have a World Health Organisation performance status of 0, 1 or 2 and at least one lesion that can be accurately assessed at baseline and is suitable for repeated assessment according to Response Evaluation Criteria in Solid Tumours (RECIST 1.1) guidelines.

Specific aims: The primary objective is to demonstrate the superior PFS of patients treated with fulvestrant 500 mg versus patients treated with anastrozole 1 mg. Secondary objectives include comparison of the overall survival (OS), the objective response rate (ORR), the clinical benefit rate (CBR) and quality of life (QoL) between the treatment groups, as well as safety and tolerability assessments.

Statistical methods: Comparison of PFS and OS for fulvestrant 500 mg versus anastrozole 1 mg will be performed using a stratified log-rank test. A multiple testing procedure will be used to control the overall type 1 error rate at 2.5% (1-sided). Results will be presented as an estimated hazard ratio, associated confidence interval and p-value. ORR and CBR will be analysed using a logistic regression model and examination of the odds ratio of the 2 treatment groups. A time to deterioration analysis will be performed for QoL endpoints.

Present accrual and target accrual: Recruitment is currently ongoing; on June 6, 2013, 101 patients had been randomised. The recruitment target is 450 patients; 124 study sites worldwide are currently initiated.

Contact information: Please contact the authors for specific information about this study.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr OT3-2-09.

Abstract PD1-4: A phase I study of BKM120 and fulvestrant in postmenopausal women with estrogen receptor positive metastatic breast cancer

Background

BKM120, a pan-Phosphatidylinositol-3-kinase (PI3K) inhibitor, in combination with fulvestrant (F) induced synergistic apoptotic effect in preclinical studies of estrogen receptor positive (ER+) breast cancer. We therefore conducted a phase I trial of BKM120 and F in postmenopausal women with ER+ metastatic breast cancer (MBC) to determine the maximum tolerated dose (MTD) and the tolerability of this combination.

Methods

A standard 3+3 phase I design was chosen for phase IA to determine the MTD. Upon completion of phase 1A, an expansion cohort phase IB was initiated to further assess the tolerability and efficacy. Patients (pts) with ER+ MBC with measurable disease were eligible. No more than 3 lines of systemic therapy in the metastatic setting were allowed in phase 1B. Cycle (C) length was 28 days. Adverse events (AEs) were assessed using CTCAE 4.0. Tumor measurement occurred every 3 cycles.

Results

Since November 2011, 18 pts (median age: 60 (range 48-71) years) were treated at 3 dose levels (DL) of BKM120 [Table 1]. Since none of the 3 pts enrolled at the starting dose of BKM120 (DL1: 80mg daily) experienced any DLT during C1, 3 pts were then enrolled at DL2 (BKM120 100 mg daily). No DLT was observed in C1, however 2 experienced grade (G) 3 ALT elevation during C2. Therefore, 3 pts were treated with BKM120 100mg 5 days on and 2 days off schedule (DL2b), without any significant AEs. Subsequently Phase IB enrolled 9 pts at this dose level.

Across different DLs, most AEs were G1. MTD was not reached based on C1 toxicity. However, asymptomatic ALT elevations occurred frequently during C2, resulting in dose interruption and dose reductions of BKM120 [Table 1]. Other AEs led to dose interruption and reductions include G2 confusion, G2 hyperglycemia and G3 rash. However, only 2 pts discontinued treatment due to AEs.

Table 1 Dose Level and Adverse EventsPhase IANBKM120No. pts dose reduced (AE, Cycle)No. pts discontinued (AE, Cycle)DL1380mg daily1 (G3 ALT, C2)1 (G2 confusion, C2)DL23100mg daily1 (G3 ALT, C2), 1 (G3 ALT, C2; G3 Rash, C7)0DL2b3*100mg daily, 5/700Phase IB (DL2b)9100mg daily, 5/71 (G3 ALT, C2; G3 Rash, C4), 1 (G2 ALT, G3 hyperglycemia, C2)1 (G4 ALT, C2)* 1 pt started DL2 in C1, then switched to DL2b following an amendment

Eleven pts with a median of 2 prior endocrine therapy (range 1-9) and 0-1 chemotherapy regimens in the metastatic setting were evaluable for response [Table 2]. Among these pts, 6 had prior disease progression on F. Clinical benefit was observed in 6 (54.5%) pts, including 1 partial response (PR) and 5 prolonged SD lasting for at least 6 cycles. Eight pts continue to receive treatment to date. Data will be updated at the time of presentation.

Table 2 ResponsePhaseDLEval. pts (N)Best responseDuration on study (mon)IA11PD3  1SD19+ 21PD1  2SD9, 7 2b1PR12IB2b5SD4+, 6, 6, 10+, 11++ treatment ongoing

Conclusion

BKM120 100mg, administered daily or intermittently, plus F was tolerable without DLT during C1. Grade 2/3 ALT elevation was common in C2, especially with daily dosing, but most pts continued treatment with reduced dose of BKM120. Promising activity was observed in this Phase I trial. Phase III studies of this combination have been started in ER+ MBC.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr PD1-4.

Can thyroid hormone mimics affect thyroid hormone measurement by immunoassay?

OBJECTIVES

This study aims to determine whether the environmental pollutant and thyroid mimic, tetrabromobisphenol A (TBBPA), interferes with thyroid hormone measurement by immunoassays.

DESIGN & METHODS

Hormone-relevant concentrations of TBBPA were added to thyroid hormone-stripped human serum and subjected to 6 different thyroid hormone immunoassays.

RESULTS

TBBPA was negative in all of the thyroid hormone immunoassays tested except at very high concentration (above that expected in serum of TBBPA-exposed workers) where it gave a marginally positive result in one immunoassay (in house T4 radioimmunoassay (RIA)).

CONCLUSIONS

Serum TBBPA present as a result of workplace exposure or its use as a fabric flame retardant is very unlikely to give false positive results in thyroid hormone immunoassays.

ACOSOG Z1041 (Alliance): Cardiac events (CE) among those receiving neoadjuvant anthracyclines (A) and taxanes with trastuzumab (T) for HER2+ breast cancer

526

Background: Z1041 randomized women with HER2+ operable breast cancer to: FEC → P+T (Arm 1) or P+T → FEC+T (Arm 2). Treatment administered as 5-FU 500 mg/m2, epirubicin 75 mg/m2 and cyclophosphamide 500 mg/m2 day 1 of a 21-day cycle x 4; paclitaxel 80 mg/m2weekly x 12 and T 4 mg/kg once then 2 mg/kg weekly x 11. T was to continue q3 weeks post-op for 40 weeks. A secondary aim was to examine the cardiotoxicity (CE). Methods: Ejection fraction (EF) was measured at baseline (BL), between regimens (wk 12), prior to surgery (wk 24) and PRN. Eligibility: BL EF ≥ 55%. CEs included decline in EF of > 15%, or >10% points to a value < LLN. Reversibility was adjudicated by blinded investigators as reversible (R: recovery of EF to ≤ 5% below BL), partially reversible (PR: recovery of > 10% points from nadir, but ≤ 5% points below BL), indeterminate (IN: no additional EF data), or irreversible (IRR:follow-up EF studies showed no improvement). Results: Of the 280 patients (Arm 1: 138) who began treatment, 15 pts (Arm 1: 10; Arm 2: 5) did not receive T. The number of weeks of T was 13 (range: 1-18) in Arm 1 and 24 (range: 1-31) in Arm 2. Changes in EF and severe treatment related cardiac toxicities prior to surgery (sx) are tabled below. There were 271 pts (Arm 1: 131) who had post-BL EFs. Prior to sx, there were 11 CE (8.3%) in Arm 1 and 13 CE (9.2%) in Arm 2. CEs were R in 12 pts (Arm 1: 5; Arm 2: 7); PR in 6 pts (Arm 1: 4; Arm 2: 2); IN in 4 pts (Arm 1: 2; Arm 2: 3) and IRR in 1 Arm 2 pt. Conclusions: The number of CE events in arms 1 and 2 showed no significant difference; greater scatter was observed in arm 2 patients. While concern for late cardiac events makes ongoing cardiac surveillance prudent due to A, concomitant use of A and T appear to not be associated with increased cardiac risk. Clinical trial information: NCT00513292. [Table: see text]

ACOSOG Z1041 (Alliance): Definitive analysis of randomized neoadjuvant trial comparing FEC followed by paclitaxel plus trastuzumab (FEC → P+T) with paclitaxel plus trastuzumab followed by FEC plus trastuzumab (P+T → FEC+T) in HER2+ operable breast cancer

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Background: Neoadjuvant chemotherapy (NAC) and concomitant trastuzumab (T) have produced high pathologic complete response (pCR) rates in HER2+ breast cancers. Z1041 addresses the timing of initiation of T with NAC. Methods: Women with operable HER2+ invasive breast cancer were randomized 1:1 to: FEC → P+T (Arm 1) or P+T → FEC+T (Arm 2) where treatment was administered as 5-FU 500 mg/m2, epirubicin 75 mg/m2 and cyclophosphamide 500 mg/m2 day 1 of a 21-day cycle x 4 (FEC); paclitaxel 80 mg/m2 weekly x 12 and trastuzumab 4 mg/kg once then 2 mg/kg weekly x 11. Eligibility also included: tumor > 2 cm or a positive lymph node and left ventricular ejection fraction > 55%. The primary aim was to compare the pCR rates in the breast (pBCR) between the regimens. Secondary endpoints were pCR rate in the breast and lymph nodes (pBNCR) and safety profile. All pts who began study treatment were included in the analyses. With 128 pts per regimen, a two-sided alpha=0.05 test of proportions would have a 90% chance of detecting a difference of 20% or more in the pBCR rates, when the pBCR rate with the poorer regimen is ≤ 25%. Results: From September 15, 2007 to December 15, 2011, 282 women (Arm 1: 140 pts) were enrolled. Two pts (Arm 1) withdrew without receiving treatment. The two arms were similar in age, stage, and hormone receptor (HR) status (HR neg: 40%). The severe (grade 3+) treatment-related toxicities included: neutropenia (Arm 1: 24.6%; Arm 2: 32.4%), fatigue (Arm 1: 4.3%; Arm 2: 8.5%), and neurosensory problems (Arm 1: 3.6%; Arm 2: 4.9%). The pBCR rate and pBNCR rates (Table) were not found to differ between the two regimens (Fisher’s exact p values: 0.905 and 0.811, respectively). Conclusions: High pCR rates can be achieved with trastuzumab in combination with anthracyclines and taxanes. The pBCR or pBNCR was not different between regimens based on the timing of initiation of trastuzumab. Clinical trial information: NCT00513292. [Table: see text]