Reduction in Breast Cancer Death With Adjuvant Chemotherapy Among US Women According to Race, Ethnicity, and the 21-Gene Recurrence Score

BACKGROUND

We previously showed the 21-gene breast recurrence score (RS) has lower prognostic accuracy for non-Hispanic Black (NHB) compared with non-Hispanic White (NHW) women with estrogen receptor (ER)-positive/HER2-negative breast cancer. The purpose of this study was to determine the clinical validity of the RS for predicting chemotherapy benefit as recommended in the current NCCN Guidelines for Breast Cancer among women from diverse racial/ethnic groups.

METHODS

Using the SEER Oncotype database, we estimated propensity score-weighted hazard ratios (HRs) and 95% confidence intervals for breast cancer death with chemotherapy for women with ER-positive/HER2-negative, AJCC stages I-II, axillary node-negative, invasive breast cancer according to race/ethnicity.

RESULTS

We included 6,033 (8.2%) Asian/Pacific Islander (API), 5,697 (7.8%) NHB, 6,688 (9.1%) Hispanic, and 54,945 (74.9%) NHW women. Breast cancer death was reduced with chemotherapy for NHB (HR, 0.48, 95% CI, 0.28-0.81), Hispanic (HR, 0.48; 95% CI, 0.25-0.94), and NHW (HR, 0.80; 95% CI, 0.65-0.99) women with an RS of 26 to 100. There was a nonsignificant reduction for API women (HR, 0.59; 95% CI, 0.28-1.24). For women with an RS of 11 to 25, there was no reduction in death for any racial/ethnic group. Among women aged ≤50 years, the reduction in breast cancer death with chemotherapy differed according to race (NHB: HR, 0.37 [95% CI, 0.20-0.67]; NHW: HR, 0.56 [95% CI, 0.44-0.74]; Pinteraction for chemotherapy * race <.0499). An exploratory subgroup analysis found that young NHB women may benefit from chemotherapy at a lower RS cutoff than other women.

CONCLUSIONS

The RS was clinically validated as a predictive biomarker for NHB, Hispanic, and NHW women with ER-positive, axillary node-negative breast cancer, but it may underestimate the benefit of chemotherapy for young NHB women. If this finding is confirmed, the RS cutoff for recommending adjuvant chemotherapy for young NHB women with ER-positive, axillary node-negative breast cancer may need to be lower than for other women.

Abstract 4090: Creating research quality cancer genomic data from electronic health records

Background: Understanding the impact of precision medicine on medical practice, patient care, and clinical outcomes is a priority for advancing cancer care. With the recent dramatic increase in the use of tumor genomic testing (TGT), records within EHRs are a rich data source for evaluating the impact of TGT results in real-world clinical practice of care and on patient outcomes. However, extracting TGT results from electronic health records (EHR) is challenging due to a lack of standards to communicate genomic information and an inability to store such information in commonly available EHR systems. Moreover, TGT results are delivered to clinicians in unstructured formats and image-based files (PDFs). We initiated a pilot study to assess the ability of natural language processing (NLP) algorithms to convert EHR unstructured clinical text and PDF-formatted TGT results into research-quality data.

Methods: One author (RY) drew a sample of approximately 800 clinical text records from 21 breast cancer patients treated at University of Washington. Sources used for data extraction included medical record notes and PDF reports for two breast cancer gene expression tests: 21-gene Recurrence Score (RS, OncotypeDx) and/or the 70-gene signature (MMP, Mammaprint). A team redacted all PHI and provided records to a commercial collaborator (Pangaeadata.AI, UK), along with definitions of variables to be extracted, but without annotated target answers. Existing NLP algorithms that leverage pre-training, fine-tuning and rules were adapted to extract 26 variables specified by the research team (e.g., age at diagnosis, histology, and RS or MMP dates and scores). The output placed variables into relevant, standardized formats and produced a research quality data set. The extraction strategy depended on the feature and variable characteristics. For example, cancer stage, an ordinal numerical variable, was determined with a rule-based extraction method from outpatient clinic notes and pathology reports, whereas the RS score, a continuous variable, came from OncotypeDx PDF and OCR semi-structured retrieval produced the output.

Results/Conclusions: The Pangaea tool obtained an average accuracy of 97.3% with a standard deviation of 3.5% across all 26 variables. The approach is developed based on rules designed and validated by clinical experts, using a model that does not require training, making overfitting likely minimal. Qualitative analysis showed that: 1] algorithms used to electronically extract TGT results provided the same data as manual abstraction by physicians, and 2] context matters, namely, the capability of preliminary semantic understanding in the Pangaea model using contextual words and phrases contributed to high accuracy and can be generalized further with larger datasets. Expansion to other health care data systems is needed to assess scalability of these technologies to create research-quality data fit for use.

Citation Format: Rachel Yung, Kari A. Stephens, Meliha Yetisgen, Andrea Burnett-Hartman, Ashwani Tanwar, Guilherme Freire, Atri Sharma, Jingqing Zhang, Vibhor Gupta, Yike Guo, VK Gadi, Larry Kessler. Creating research quality cancer genomic data from electronic health records [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 4090.

Clinical Validation of a Circulating Tumor Cell Assay Using Density Centrifugation and Automated Immunofluorescence Microscopy

OBJECTIVES

The US Food and Drug Administration (FDA)-approved CELLSEARCH assay (Menarini Silicon Biosystems) for circulating tumor cells (CTCs) relies on expression of an epithelial cell adhesion molecule to enrich for CTCs. We sought to validate a CTC assay (RareCyte) for clinical use that instead collects a buffy coat preparation enriched for CTCs.

METHODS

Normal peripheral blood specimens spiked with cultured breast and prostate cancer cells and 47 clinical samples were used to validate assay performance. Specimens were enriched for buffy coat cells and applied onto 8 glass slides. The slides were immunofluorescently stained and imaged by automated microscopy and computer-aided image analysis.

RESULTS

The assay was 100% specific for detecting spiked tumor cells. For samples spiked with 25, 50, and 125 cells, the percentage coefficients of variation were 42%, 21%, and 3.7%, respectively. Linearity studies demonstrated a slope of 0.99, an intercept of 1.6, and R2 of 0.96. Recoveries at the 25-, 50-, and 125-cell levels were 92%, 111%, and 100%, respectively. Clinical samples run on both CELLSEARCH and RareCyte correlated with an R2 of 0.8 after log-transformation and demonstrated 87.5% concordance using the CELLSEARCH criteria for predicting adverse outcomes.

CONCLUSIONS

The RareCyte CTC assay has comparable performance to the FDA-cleared method and is ready for further clinical validation studies.

Abstract P5-07-05: Deciphering the inferior prognosis of young women with estrogen receptor-positive early-stage breast cancer through full transcriptome analysis: A FLEX database sub-study

Introduction: Young women with estrogen receptor (ER)-positive early-stage breast cancer (EBC) frequently present with larger, higher-grade, more aggressive tumors, with lower ER expression than older women. Post-hoc analyses within the MINDACT and TAILORx cohorts reported that women aged 40-50 with ER+ EBC exhibited a chemotherapy benefit independent of genomic risk compared to women aged &gt; 50, possibly due to chemotherapy-induced ovarian suppression (CIOS). However, women &lt; 40 years, who seldom develop CIOS, are under-represented in clinical trials. Therefore, it is important to distinguish the tumor biological profile within this younger age group. To understand the biological basis underlying why younger women have poorer outcomes than older women, this study aimed to identify genes that distinguish tumors in younger women from older women. Methods: EBC patients enrolled in the FLEX study (NCT03053193) undergo standard of care MammaPrint (MP) and BluePrint (BP) tests, and consent to clinically annotated whole transcriptome data collection. MP categorizes tumors as High Risk (HR) or Low Risk (LR) of recurrence. Together, MP and BP classify molecular subtype as Luminal A, Luminal B, HER2, or Basal. Whole transcriptome gene expression differences were compared among ER+ tumor specimens from three age groups: &lt; 40 years old (n=283), 40-54 years old (n=1535), and ≥ 55 years old (n=4355). Differentially expressed genes (DEGs) were identified from 100 randomized iterations for each comparison; an equal number of LR and HR samples were analyzed in each group. DEGs found in &gt; 20 iterations indicated gene stability within the age group. DEGs were also identified within each age group after correcting for BP subtype, and between pre-menopausal (n=1314) and post-menopausal (n=4859) women. Gene expression data were quantile normalized using R package ‘limma’. DEGs with an adjusted p&lt;0.05 and fold change ≥ 2 were considered significant. Results: Overall, 76.0% of women &lt; 40 years, 53.6% of women aged 40-54, and 48.5% of women ≥ 55 years had MP HR tumors. In addition, women &lt; 40 years had higher frequencies of BP Basal and HER2 tumors (20.5% and 9.2%, respectively) compared with women ≥ 55 years (8.0% and 2.4%, respectively; p&lt;0.0001). In line with unsupervised hierarchical clustering and previous studies, tumors from patients aged 40-54 exhibited limited DEGs in comparison to women ≥ 55 years. In contrast, most gene expression differences were primarily observed between women &lt; 40 and ≥ 55 years (11 DEGs; 10 downregulated and 1 upregulated). We identified limited DEGs within BP Luminal A (n=23), Luminal B (n=10), and Basal (n=7) tumors from women aged &lt; 40 relative to women ≥ 55 years. No DEGs were found in HER2-type tumors. Within Luminal A and Basal tumors, upregulated genes in women &lt; 40 years are important for proliferation and immune responses. Luminal B tumors in women aged &lt; 40 have increased DEGs involved in ER and HER2 signaling. Within all subtypes, DEGs supporting metabolic functions were downregulated in tumors of women &lt; 40 years compared with women ≥ 55 years. Few DEGs were observed between pre-menopausal women and post-menopausal women, though none with &gt; 2-fold change. Conclusion: Tumors from women aged 40-54 had few DEGs, suggesting observed chemotherapy benefit represents differences in host biology rather than intrinsic tumor biology as compared with tumors from women &lt; 40 or ≥ 55, where detected DEGs are associated with proliferation, receptor signaling, and metabolism. Fewer DEGs were observed by menopausal status than age, indicating age is a more relevant cutoff. Future studies will aim to further characterize this high risk young patient population.

Citation Format: Shubhada Dhage, Mina Gendy, Nina D'Abreo, Ruth Oratz, Sami G. Diab, VK Gadi, Cathy Graham, Midas Kuilman, Shiyu Wang, Patricia Dauer, Andrea Menicucci, William Audeh, Douglas K. Marks. Deciphering the inferior prognosis of young women with estrogen receptor-positive early-stage breast cancer through full transcriptome analysis: A FLEX database sub-study [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P5-07-05.

A Phase II Study Evaluating the Safety and Efficacy of Sunitinib Malate in Combination With Weekly Paclitaxel Followed by Doxorubicin and Daily Oral Cyclophosphamide Plus G-CSF as Neoadjuvant Chemotherapy for Locally Advanced or Inflammatory Breast Cancer

INTRODUCTION

Neoadjuvant chemotherapy is standard treatment for locally advanced breast cancer (LABC) or inflammatory breast cancer (IBC). We hypothesized that adding sunitinib, a tyrosine kinase inhibitor with antitumor and antiangiogenic activity, to an anthracycline and taxane regimen would improve pathologic complete response (pCR) rates to a prespecified endpoint of 45% in patients with HER2-negative LABC or IBC.

METHODS

We conducted a multicenter, phase II trial of neoadjuvant sunitinib with paclitaxel (S+T) followed by doxorubicin and cyclophosphamide plus G-CSF for patients with HER2-negative LABC or IBC. Patients received sunitinib 25 mg PO daily with paclitaxel 80 mg/m² IV weekly ×12 followed by doxorubicin 24 mg/m² IV weekly + cyclophosphamide 60 mg/m² PO daily with G-CSF support. Response was evaluated using pCR in the breast and the CPS + EG score (clinical-pathologic scoring + estrogen receptor [ER] and grade).

RESULTS

Seventy patients enrolled, and 66 were evaluable for efficacy. Eighteen patients (27%) had pCR in the breast (10 had ER⁺ disease and 8 had triple-negative disease). When defining response as pCR and/or CPS + EG score ≤2, 31 (47%) were responders. In pateints with ER positive disease, 23 (64%) were responders. The most common toxicities were cytopenias and fatigue.

CONCLUSIONS

Neoadjuvant S+T followed by AC+G-CSF was safe and tolerable in LABC and IBC. The study did not meet the prespecified endpoint for pCR; however, 47% were responders using pCR and/or CPS + EG score ≤2. ER positive patients had the highest response rate (64%). The addition of sunitinib to neoadjuvant chemotherapy may provide promising incremental benefit for patients with ER positive LABC.

Abstract CT260: The FLEX real-world data platform explores new gene expression profiles and investigator initiated protocols in early stage breast cancer

Background: Genomic expression profiling has significantly improved the personalized treatment of breast cancer, by providing prognostic information about the metastatic potential of tumors and enabling the classification of breast cancers into molecular subtypes, beyond clinical and pathological factors. When combined with comprehensive clinical data, full genome expression data can precisely stratify tumors into clinically actionable subgroups. The FLEX Study is aggregating a large, real-world dataset, which will enable the discovery of novel genomic profiles to improve precision in the management of breast cancer, particularly in patient subsets that are underrepresented in traditional clinical trials. Methods: The FLEX Study (NCT03053193) is a multicenter network, prospective, observational trial for patients with stage I-III breast cancer whose primary tumor is analyzed by MammaPrint, with or without BluePrint. The primary objective of FLEX is to create a large scale, population-based registry that links comprehensive clinical data with full genome expression data to elucidate new prognostic and/or predictive gene associations in a real-world setting. The FLEX Study employs a shared study infrastructure to develop and investigate hypotheses for targeted subset analyses and/or clinical trials based on genomic data. The adaptable protocol is designed to be amended to include additional targeted sub-studies, allowing participating investigators to leverage data within the FLEX network to investigate research questions. Patients enrolled in the initial study are eligible for inclusion in sub-studies for which they meet all eligibility criteria and additional consent is not required. Data is collected on patients from diagnosis through 10 years of follow-up and any necessary additional clinical data will be collected as specified in the appendix protocols. The target enrollment of FLEX is a minimum of 10,000 patients; over 6,500 patients have enrolled since April 2017 at more than 85 sites, including eight National Cancer Institute-designated comprehensive cancer centers. The FLEX collaborative platform allows participating investigators the opportunity to author their own sub-study protocols, as approved by the FLEX Scientific Review Committee. Sub-study research categories include: Age and Breast Cancer, Optimizing Therapy Strategies, Breast Cancer and Metabolic Syndrome, ctDNA and Liquid Biopsy, Genomics and Subtypes, Social and Ancestry, and Neoadjuvant Therapy and Surgery. To date, 29 investigator-initiated sub-studies have been approved. Trial contact information: NCT03053193 FLEX@agendia.com

Citation Format: Adam Brufsky, Jennifer A. Crozier, Nina D'Abreo, Mehran Habibi, Sami Diab, Joyce O'Shaughnessy, Douglas K. Marks, VK Gadi, Amy M. Truitt, Lisa Blumencranz, Erin Yoder, William Audeh, Sarah Untch, Bastiaan van der Baan, FLEX Investigators' Group. The FLEX real-world data platform explores new gene expression profiles and investigator initiated protocols in early stage breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr CT260.

Abstract 6442: Investigation of custom biomarkers on circulating tumor cells from clinical samples using RarePlex® Developer Kits

Enumeration and phenotypic profiling of circulating tumor cells (CTCs) can give important information about tumor progression, presence of therapeutic targets, and metastatic potential. New and informative cancer-specific biomarkers are being discovered at a rapid pace, so there is a strong need for tools that enable investigator driven assays to best study and utilize these biomarkers. Through the RareCyte platform, we provide sensitive and specific assays that are optimized and validated for CTC enumeration and biomarker expression. RarePlex Developer Kits enable the addition of user-selected antibodies against biomarkers of interest to a CTC detection assay. Here we demonstrate the application of RarePlex Developer Kits to study the presence of a variety of cancer related biomarkers. Using the Developer strategy, we present results for several biomarkers, including HER2, ER, PR, EGFR, Ki67, AR, ARv7, PDL1, and PSMA. We also characterized clinical samples from prostate (AR and ARv7) and breast (HER2 and ER) cancer patients. The biomarkers demonstrated proper localization on or within model CTC control cells when using default antigen retrieval and fixation conditions. For each biomarker, fluorescence intensity cut-offs that segregated negative and positive cell lines were statistically defined to maximize classification accuracy. For clinical samples, breast and prostate cancer sample staining showed expected localization based on available clinical information. In conclusion, RarePlex Developer Kits provide a flexible tool for custom CTC assay development that enables researchers to develop assays in their own lab for characterization of phenotypic heterogeneity.

Citation Format: Edward Lo, Daniel Campton, Arturo Ramirez, Lillian Costandy, Brady Gardner, Ryan Houston, Heather Itamoto, Jeffery L. Werbin, VK Gadi, Tanisha Mojica, Alisa Clein, Celestia Higano, Daniel E. Sabath, Eric P. Kaldjian, Tad George. Investigation of custom biomarkers on circulating tumor cells from clinical samples using RarePlex® Developer Kits [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6442.

Abstract P4-04-03: High-throughput epigenetic screening in hormone receptor positive (HR+) breast cancer cells

Background & Objective: Substantial progress has been made in treating HR+ metastatic breast cancer patients with CDK4/6, mTOR and PIK3CA inhibitors (all FDA approved), but there are no current available therapies to directly restore sensitivity to endocrine therapy once patients’ cells develop epigenetic suppression of ER pathways. CCCTC-binding factor (CTCF), which regulates higher-order chromatin organization and estrogen reception (ER) transcription, is altered by hemizygous deletion or mutation in more than 50% of HR+ luminal type breast tumors. The goal of this project is to characterize an epigenetic signature in CTCF-altered breast cancers to identify novel epigenetic targets for therapeutics development. Targeting CTCF influenced pathways with or without its chaperones may restore sensitivity to endocrine therapy in patients with HR+ breast cancer.

Methods: We identified patient-derived cell lines from the Cancer Cell Line Encyclopedia (CCLE) with known CTCF gene copy number. Selected cell lines were tested for proliferation with a custom siRNA library targeting 1,300 genes involved in epigenetic regulation while in the presence of different concentrations of estradiol, tamoxifen and fulvestrant. We confirmed presence of CTCF protein by western blot and mRNA expression by real-time PCR. Proliferation of the lines in vitro was quantified by the MTT assay. Further functional annotation and pathway enrichment analysis of the identified genes were performed by using the g:ProfileR package.

Results: We have screened more than 60 breast cancer cell lines and focused on six HR+ luminal (3 each “a” and “b” type) lines with different levels of CTCF copy number; a normal breast epithelial line was used as control. We observed that cell growth responded to anti-estrogen therapy differently based on the copy number of CTCF. Cells with high copy number of CTCF are resistant to endocrine therapy, the sensitivity was restored by silencing CTCF using siRNA. We then selected two cell lines with low and high copy number of CTCF for further high-throughput screening with the epigenetic siRNA library. A total of 67 and 35 candidate sensitizer target genes, and 56 and 44 candidate enhancer target genes were prioritized in cells with low and high copy number of CTCF, respectively. Functional annotation and pathway enrichment analysis of the identified genes showed that cells with low copy number of CTCF had apoptosis related hits, such as BCL family and caspase genes; however, cells with high copy number of CTCF were found to relate to other epigenetic regulators such as DNMTs and CHD. This suggests that CTCF might form complexes with other epigenetic proteins to form abnormal chromatin configuration with abnormal regulation of ER pathway as consequence.

Conclusions: To our knowledge, this is the first epigenetic library screen of HR+ luminal breast cancer cells with responses categorized by differential CTCF copy number status. We have confirmed CTCF as an important protein in predicting response to endocrine therapy and identified possible interactions between CTCF, DNMT and CHD. We conclude that development of therapeutics against targets identified in our screen to reverse endocrine resistance may be achievable for treatment of luminal breast cancers that undertake epigenetic deregulation.

Keywords: Breast cancer; Hormone receptor positive; epigenetic screening

Citation Format: Fengting Yan, Olga Nikolova, VK Gadi. High-throughput epigenetic screening in hormone receptor positive (HR+) breast cancer cells [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 P4-04-03.

Abstract P6-10-17: Breast MRI as a radiomic biomarker of immune response in HER2+ breast cancer

Rationale/Objectives: Tumor immune infiltration in HER2+ breast cancer is associated with improved outcomes and better responses to treatment with drugs such as trastuzumab. Breast MRI is a non-invasive technique that is part of the standard evaluation for localized breast cancer. Breast MRI dynamic-contrast enhanced (DCE) and diffusion-weighted imaging (DWI) sequences may detect immune responses in the tumor microenvironment. Apparent diffusion coefficient (ADC), which is derived from DWI, has been associated with tumor cellularity. In this pilot study, we hypothesized that patients with low ADC would be more immune responsive (i.e. have greater TIL infiltration) to trastuzumab. We also performed an exploratory analysis looking at differences in the expression of immune-relevant genes between “low” and “high” ADC patients.

Methods: Patients with localized HER2+ breast cancers 10 mm or larger and planned for curative-intent therapy were eligible to enroll. After enrollment, patients received a single run-in dose of trastuzumab with paired breast MRI exams before and after treatment that included DCE and DWI sequences. Post-trastuzumab tissue was obtained from the patient’s surgical specimen or from a second biopsy (if planned for additional neoadjuvant treatment). MRI images were analyzed to measure the functional tumor volume and peak signal enhancement ratio from DCE and mean apparent diffusion coefficient (ADC) from DWI. TIL content was assessed by a breast pathologist in both the pre- and post-trastuzumab tissue specimens. The pre- and post-treatment samples were also analyzed using an immune-focused RNA-based multiplex gene expression assay.

Results: Twelve women have enrolled to date with a median age of 53 years (range 37-70 years old). Five out of the twelve patients (42%) had estrogen-receptor negative tumors. For the 8 patients with pre- and post-treatment tissue currently available for analysis, the average pre-treatment TIL percentage was 22% (range 1-70%), the average post-treatment TIL percentage was 42% (range 1-90%), and the average absolute increase between pre- and post-treatment TILs was 20% (range 0%-58%). Pre- and post-treatment ADC showed a strong negative correlation with the increase in TIL content after trastuzumab treatment (r = -0.71 and r = -0.93, respectively).

At submission, preliminary gene expression analysis of pre- and post-treatment tissue is available in 6 patients. The patients were binned into “high” and “low” ADC groups with the median pre-treatment ADC as the cut-off. The magnitude of change in gene expression after trastuzumab treatment (small vs large change) clustered by high or low pre-treatment ADC; this suggests that pre-treatment ADC may differentiate between two distinct immune phenotypes. Further analysis showed that the low ADC group had relatively higher pre-treatment gene expression of CD8, CD4, and CD19 (T and B cell markers) when compared to the high ADC group. The low ADC group also had a decrease in FoxP3 expression (regulatory T cell marker) versus the high ADC group, which had an increase in FoxP3 expression. The high ADC group also had a notable increase in CCR4 expression (associated with a TH2 type immune response), while the low ADC group did not have an increase. The combination of an increase in FoxP3 expression and an increase in CCR4 expression suggests that the high ADC group may have a more immune-inhibited microenvironment in response to trastuzumab.

Conclusions: These initial analyses suggest that the pre-treatment ADC calculated from DWI may identify HER2+ breast cancers that will have an anti-tumor immune response to trastuzumab therapy. Final data from the full planned cohort will be presented at the meeting and include discussion of the DCE metrics. Based on this preliminary data, further study of breast MRI as an immune biomarker is warranted.

Citation Format: Laura Carpin Kennedy, Grace Durenberger, Sasha E. Stanton, Shaveta Vinayak, Suzanne Dintzis, Savannah Partridge, VK Gadi. Breast MRI as a radiomic biomarker of immune response in HER2+ 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 P6-10-17.

Abstract GMM-051: A CLIA-CERTIFIED HIGH-THROUGHPUT DRUG SCREENING PLATFORM FOR OVARIAN CANCER TO INFORM PERSONALIZED CANCER CARE AND DISCOVER NOVEL COMBINATIONS

BACKGROUND: Metastatic disease in ovarian cancer is difficult to treat and patients often exhaust standard-of-care regimens. To gain a better understanding of potential treatments, genomic data can be used. However, the interpretation of the genomic data for ovarian cancer is challenging given complex mutation patterns and the absence of recurrent druggable alterations beyond DNA repair deficiency. Here we present the first CLIA certified high-throughput functional assay employing organoid cultures derived from primary patient specimens to directly aid oncologists for personalized treatment selection in combination with genomic data (P.A.R.I.S® Assay, SEngine Precision Medicine, Seattle, WA).

EXPERIMENTAL PROCEDURES: Organoids are exposed to a library of 123 clinically relevant drugs. The library was developed to include chemotherapies and FDA approved drugs currently used in the clinic, as well as promising drugs undergoing clinical trials. Compounds are evaluated at a multi-dose response curve and ranked by SPM™ score, which weighs both the sensitivity (degree of cell death) and specificity, which compares the response of the patient's tumor cells to the drug relative to all prior patients. In addition to single agent screens, optimal combinations can also be tested. The results are further integrated with genomic data when available, and drug-responses are reported to the clinician. SEngine has performed &gt;200 drug screens across &gt;20 different tumor types and established high reproducibility of the high-throughput platform. Ovarian samples were derived from either ascites or biopsies.

RESULTS: Of the 7 samples directly derived from patients, 1 was from ascites, 4 were from biopsies or surgical excisions, and 2 had both. In addition, 13 cell lines were screened with the SEngine drug library. While every patient exhibited a unique pattern of response consistent with the heterogeneity of the complex genetic landscape of ovarian cancer, sensitivities for certain drugs such as HDAC, PI3K and tyrosine-kinase inhibitors were frequently found. Several n=1 cases will be presented to highlight correlations with retrospective clinical responses as well as with genomic alterations. These results highlight how genomic data and functional testing can be combined to optimize personalized cancer care.

To identify optimal drug combinations with PARP inhibitors, we have performed an unbiased screen where patient derived ovarian cancer cell lines were challenged with SEngine drug library in the presence of rucaparib. The screen indicated multiple drugs, such as bromodomain, BCL2 and cyclin dependent kinase (CDK) inhibitors as well as dasatinib as potential sensitizers to rucaparib. Confirmation of these results in additional patient derived organoids and PDX models are in progress.

IMPACT: We developed a robust ex vivo screening platform to objectively quantify patient specific sensitivity to a panel of more than 123 oncology drugs and potential novel combinations. SEngine is compiling a registry capturing clinical data, outcome following the P.A.R.I.S® test, and genomic data. Combining the power of high-throughput technology and organoid isolation with genomic data will enable the rapid selection of optimal individualized therapies as single agents or in combination and guide design of future clinical trials.

Citation Format: Franz X Schaub, Sabrina Maisel, Reid Shaw, Rachele Rosati, Caroline Bridgwater, Michael Churchill, Robert Diaz, Stephanie Tatem Murphy, Shalini Pereira, Christopher Kemp, VK Gadi, and Carla Grandori. A CLIA-CERTIFIED HIGH-THROUGHPUT DRUG SCREENING PLATFORM FOR OVARIAN CANCER TO INFORM PERSONALIZED CANCER CARE AND DISCOVER NOVEL COMBINATIONS [abstract]. In: Proceedings of the 12th Biennial Ovarian Cancer Research Symposium; Sep 13-15, 2018; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2019;25(22 Suppl):Abstract nr GMM-051.

Discovery of novel bacterial queuine salvage enzymes and pathways in human pathogens

Queuosine (Q) is a complex tRNA modification widespread in eukaryotes and bacteria that contributes to the efficiency and accuracy of protein synthesis. Eukaryotes are not capable of Q synthesis and rely on salvage of the queuine base (q) as a Q precursor. While many bacteria are capable of Q de novo synthesis, salvage of the prokaryotic Q precursors preQ0 and preQ1 also occurs. With the exception of Escherichia coli YhhQ, shown to transport preQ0 and preQ1, the enzymes and transporters involved in Q salvage and recycling have not been well described. We discovered and characterized 2 Q salvage pathways present in many pathogenic and commensal bacteria. The first, found in the intracellular pathogen Chlamydia trachomatis, uses YhhQ and tRNA guanine transglycosylase (TGT) homologs that have changed substrate specificities to directly salvage q, mimicking the eukaryotic pathway. The second, found in bacteria from the gut flora such as Clostridioides difficile, salvages preQ1 from q through an unprecedented reaction catalyzed by a newly defined subgroup of the radical-SAM enzyme family. The source of q can be external through transport by members of the energy-coupling factor (ECF) family or internal through hydrolysis of Q by a dedicated nucleosidase. This work reinforces the concept that hosts and members of their associated microbiota compete for the salvage of Q precursors micronutrients.

Abstract P2-08-42: Use of breast cancer index to analyze tumor proliferation and endocrine responsiveness in genomic intermediate risk patients

Background: Breast Cancer Index (BCI) is a genomic assay that stratifies patients (pts) for cumulative 10-year and late (post–5-year) risk of distant recurrence and predicts the likelihood of extended endocrine therapy (EET) benefit based on the algorithmic analysis of gene expression from two functional gene cassettes: 1) The Molecular Grade Index (MGI), which contains 5 proliferation genes and 2) The HoxB13/IL17BR (H/I) ratio, an endocrine response biomarker. BCI more precisely resolves genomic intermediate risk patients into low- and high-risk groups (Sestak, Clin Cancer Res 2016) and adds significant prognostic data beyond clinical features (ie, clinical treatment score; Sestak, JAMA Oncol 2017) by interrogating different aspects of tumor biology such as proliferation and endocrine response. The objective of this study was to measure tumor proliferation and endocrine responsiveness using MGI and H/I respectively and evaluate their correlation with age in genomic intermediate risk pts.

Methods: This study utilized a subset of cases from the BCI Clinical Database for Correlative Studies, an IRB-approved de-identified database that contains clinicopathologic and molecular variables from clinical cases submitted for BCI testing. Genomic intermediate risk cases were defined as LN-, HER2- (or HER2 status unknown) with 21-gene recurrence scores (RS) of 11 to 25 using cut-points from the TAILORx study. Quantitative scores for MGI and H/I were derived by algorithmic analysis of BCI gene expression. Age groups (&lt;50y and ≥51y) were determined using the date of diagnosis. MGI and H/I were evaluated in two different genomic intermediate risk groups: RS 11-15 and RS 16-25. Pearson correlation coefficients were used to determine the correlation between MGI, BCI, H/I, and genomic intermediate risk scores for patients &lt;50y and ≥51y.

Results: Of the 441 pts with RS and BCI results, 303 (69%) with genomic intermediate risk were analyzed. The median MGI score in pts ≥51y was higher in the RS 16-25 group compared to RS 11-15, but there was no difference in MGI score between the two genomic intermediate RS risk groups for pts &lt;50y. In contrast to MGI, median H/I was higher in the RS 16-25 group irrespective of age, with 37% of pts &lt;50y and 41% of pts ≥51y having tumors predicted as more likely to benefit from EET using validated cut-points for H/I. There was no significant correlation between tumor proliferation (MGI: r=0.166) or endocrine responsiveness (H/I: r=0.244) with genomic intermediate-risk RS 11-25 group.

Conclusion: These data, which show variations in tumor proliferation and endocrine signaling based on age and genomic intermediate risk group, highlight the importance of measuring different features of tumor biology for risk classification and prediction of therapy response. The absence of correlations between tumor proliferation and genomic intermediate risk and age, and between estrogen signaling and genomic intermediate risk and age, suggests that assays such as BCI that combine distinct aspects of tumor biology for prognosticating risk of recurrence and prediction of benefit from endocrine therapy provide additional value for individualizing the management of patients with early-stage ER+ breast cancer.

Citation Format: Yan F, Master AK, Israel MA, Liu J, Zhang Y, Schnabel CA, Gadi VK. Use of breast cancer index to analyze tumor proliferation and endocrine responsiveness in genomic intermediate risk 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 P2-08-42.

Abstract P1-14-02: A phase 2 study of low dose metronomic eribulin in metastatic breast cancer

Background: Eribulin mesylate is a non-taxane microtubule dynamics inhibitor approved by FDA in treatment of metastatic breast cancer (MBC) based on improvements in overall survival in the pivotal EMBRACE trial. Eribulin is approved at 1.4mg/m2 administered D1,8 of q21d cycle. However, this dose and schedule may have significant myelosuppression and peripheral neuropathy requiring dose reductions and treatment delays for some patients. We hypothesized that a low dose metronomic schedule will allow responding patients to remain on treatment, resulting in longer TTP (time to progression) and decreased incidence of toxicities and treatment-related discontinuations.

Methods: A multi-site prospective open-label phase II trial of metronomic dosing of eribulin in patients with MBC has completed accrual of 60 patients, outcomes will be updated at presentation. Patients whose disease had progressed following 1-6 prior regimens with prior exposure to a taxane, ECOG performance status of 0 – 2, measurable disease per RECIST 1.1, with normal marrow and organ function were eligible. Eribulin was administered at 0.9mg/m2 weekly for 3 out of 4 weeks. For patients with HER2 positive disease, concurrent trastuzumab administration was allowed. Concurrent denosumab or bisphosphonates were allowed for patients with bone disease.

Results: 60 patients were enrolled, average age 58 (range 34-83). Majority were postmenopausal Caucasian females, but the study included African American, Hispanic, native American, male patients. The majority of tumors were ER+, infiltrating ductal, but the study included 13 HER2+, and 12 TN tumors, with 5 ILC, and 5 mixed ILC/IDC. Nearly half of the enrolled patients had clinical benefit from the regimen, remaining on therapy for 6 months or longer, with stable disease or response; 50% had progression PD at 3 months 32% had stable disease and 18% had a partial or complete response (1, long term). Overall Survival, OS, for the entire group of heavily pre-treated patients was 1.2 years, with TN and HER2 positive patients faring better than ER+ in this small study. One HER2+ patient remains in long-term remission, off chemotherapy.

The regimen was extremely well tolerated. The majority of the patients experienced grade 0 or 1 toxicity for alopecia (48/60) and peripheral neuropathy (7 with grade 2 neuropathy, 5 pre-existing, 2 with grade 3 neuropathy). There were few dose reductions (n=15), thrombocytopenia (11 grade 1 only), or use of G-CSF (14).

Conclusions: Metronomic weekly low dose eribulin appears to be an active and tolerable regimen with less myelosuppression, alopecia and peripheral neuropathy than is seen with approved dose, allowing longer duration of use and disease control, with similar outcomes compared to the standard dose regimen. Outcomes will be updated at presentation.

Citation Format: Chalasani P, Liu AJ, Khanjian JA, Peha M, Buening BJ, Gadi VK, Specht JM, Salazar L, Linden HM. A phase 2 study of low dose metronomic eribulin in 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 P1-14-02.

Correction to: a Phase 2 Study of 16α-[18F]-Fluoro-17β-Estradiol Positron Emission Tomography (FES-PET) as a Marker of Hormone Sensitivity in Metastatic Breast Cancer (MBC)

Two data points from Table 1. (continued) were published in error. The corrected data in Table 1. (continued) are shown, in italic, below.

Abstract 5697: Simultaneous assessment of PD-L1 and IFR1 expression on breast cancer circulating tumor cells

Background: There is a need for noninvasive predictive biomarkers of response to anti-PD1/PDL1 therapies. Assessment of circulating tumor cells (CTCs) is a rational approach to noninvasive sampling of tumors to understand the potential response or nonresponse to anti-PD1/PD-L1 therapies. IFN-gamma signals through the JAK/STAT cascade to induce PD-L1 via the Interferon Regulatory Factor-1 (IRF1) transcription factor, and is a potent inducer of PD-L1 expression in tumor cells. Recent studies have shown that low or absent IRF1 expression can identify melanomas that lack IFN-gamma responsiveness, and that IRF1 can have a higher predictive value of response to anti-PD1/PD-L1 therapy than PD-L1 itself. Using CTC models and the RareCyte platform, we developed a multiparameter assay that allows simultaneous PD-L1 and IRF1 assessment after CTC identification. We used this assay to better understand the relationship between IRF1 and PD-L1 expression in CTC model systems and applied this assay to blood samples from breast cancer patients.

Materials and Methods: Peripheral blood from normal donors or cancer patients under an IRB-approved protocol was collected into RareCyte blood collection tubes. PD-L1(+) and PD-L1(-) CTC models were created by culturing A549 overnight with or without 10ng/mL INF-gamma. The A549 cells were spiked into normal donor blood and buffy coats isolated from 7.5mL of blood by AccuCyte® separation and spread onto slides. MDA-MB-231 cells were used as a model to represent breast cancer cells that express PD-L1 in the absence of IFN-gamma signaling. Slides were stained with a 6-marker panel that included antibodies to pan-cytokeratin (CK), EpCAM, CD45, PDL1, IRF1, and a nuclear dye on the Leica Bond Rx auto-stainer. Slides were scanned with CyteFinder® and CTCs identified by CK and/or EPCAM positivity and negative CD45 staining. Confirmed CTCs were then assessed for expression of PD-L1 and IRF1; cellular compartment was recorded for IRF1 staining.

Results: Nuclear expression of IRF1 correlated with PD-L1 expression in IFN-gamma stimulated A549 cells. Unstimulated MDA-MB-231 cells expressed high levels of PD-L1, but this did not correlate with nuclear IRF1 expression. Breast cancer patient samples were identified having CTCs that expressed PD-L1. A PDL1 mean fluorescence intensity (MFI) threshold was set at the upper 95% CI of unstimulated A549 cells to define “high” and “low” PD-L1 expression in the patient samples. The population of high-PD-L1 CTCs had higher nuclear IRF1 MFI than low-PD-L1 CTCs, with mean fold-increase of 2.7 (range from 1.4 to 3.3).

Conclusions: Nuclear IRF1 expression correlates with PD-L1 expression in breast cancer CTCs. Using CTCs to evaluate expression of IRF1 and PD-L1 together with assessment of CTC mutational load could be a powerful noninvasive assessment of response to anti-PD1/PD-L1 therapies.

Citation Format: Lance U'Ren, Nolan Ericson, Ryan Huston, Elisabeth Mahen, VK Gadi, C. Anthony Blau, Eric Kaldjian. Simultaneous assessment of PD-L1 and IFR1 expression on breast cancer circulating tumor cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5697.

Abstract P1-06-10: Correlative analysis of breast cancer index (BCI) restratification of 21-gene recurrence score (RS) in patients with hormone receptor-positive (HR+), node-negative breast cancer

Background: In a cross-stratification analysis performed within the TransATAC cohort, Breast Cancer Index (BCI) and 21-gene Recurrence Score (RS) had a concordance of 58.2% (Sestak et al., Clin Cancer Res, 2016). Restratification by BCI of the low and intermediate RS risk groups led to subgroups with significantly different rates (P &lt; 0.001 and P = 0.003, respectively); in contrast, restratified subgroups created by RS of BCI risk groups did not differ significantly. The objective of this study was to analyze the concordance of BCI and RS test results in HR+, node-negative (LN-) patients tested in the real-world setting and to investigate molecular, clinical, and pathologic correlates within discrepant cases.

Methods: This study utilized a subset of cases from the BCI Clinical Database for Correlative Studies, an IRB-approved de-identified database which contains clinicopathologic and molecular variables from clinical cases submitted for BCI testing. Clinicopathologic variables, abstracted from pathology reports, were available for a subset of cases. This analysis evaluated cases from LN- patients with available RS data. Concordance was evaluated between BCI Prognostic risk groups (Low, High) and RS risk groups (Low, Intermediate, High based on TAILOR Rx cutpoints [0-10, 11-25, and 26+]). Fisher's Exact tests were used to compare molecular (HoxB13/IL17BR [H/I] endocrine response biomarker and Molecular Grade Index [MGI] proliferation marker) and clinicopathologic (age, grade, size, HER2, Ki67) data in discrepant risk groups.

Results: There were 456 LN- patients included. Median age was 58.0y (range 27.2-84.0y; 73.9% ≥50y); 33.1%/50.1%/16.8% were grade 1/2/3; and 24.0%/59.5%/15.3% were T1ab/T1c/T2. BCI classified 47.8% (n=218) of patients as Low Risk vs 52.2% (n=238) as High Risk. RS classified 17.1% (n=78), 67.1% (n=306), and 15.8% (n=72) of patients as Low, Intermediate, and High Risk, respectively. BCI restratified RS-Low patients as high risk in 17.1% of cases, restratified RS-Intermediate as Low Risk in 48.4% and High Risk in 51.6%, and restratified RS-High as Low risk in 20.8% of cases. In RS-Low patients, only H/I (P=0.0004) and MGI (P=0.047) were significantly correlated with restratification to BCI-High Risk. In RS-Intermediate patients, H/I (P&lt;0.0001), MGI (P&lt;0.0001), grade (P&lt;0.0001), and Ki67 &gt;20% (P=0.0003) were significantly correlated with restratification by BCI to High or Low Risk. In RS-High patients, H/I (P=0.0008), MGI (P&lt;0.0001), grade (P=0.016) were significantly correlated with restratification to Low Risk.

Conclusion: BCI restratified a substantial proportion of patients in each RS risk group. Based on previous studies demonstrating that BCI has improved prognostic ability for assessment of risk of late distant recurrence (Sgroi et al., Lancet Oncol, 2013), these results highlight the clinical utility of BCI within all RS risk groups. The estrogen signaling pathway biomarker H/I and proliferative biomarkers (MGI, grade, Ki67) were associated with restratification by BCI, while age, HER2 status, and tumor size were not.

Citation Format: Yan F, Master AK, Israel MA, Liu J, Schnabel CA, Hurvitz S, Gadi VK. Correlative analysis of breast cancer index (BCI) restratification of 21-gene recurrence score (RS) in patients with hormone receptor-positive (HR+), node-negative 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 P1-06-10.

Abstract P4-22-11: Combined targeted therapies for advanced triple negative breast cancer: A phase II trial of nab-paclitaxel and bevacizumab followed by maintenance targeted therapy with bevacizumab and erlotinib

Background: Chemotherapy remains the mainstay of therapy for patients with metastatic triple negative breast cancer (TNBC). We hypothesized that the addition of biologic agents targeting key pathways (bevacizumab targeting angiogenesis and erlotinib directed against EGFR) may prolong progression free survival (PFS) and offer a novel treatment strategy free from chemotherapy for patients with metastatic TNBC.

Methods: Patients with TNBC receiving initial therapy for metastatic disease were eligible for this multicenter phase II trial (NCT00733408) conducted at an academic center and affiliated, community practice sites. Induction therapy included nab-paclitaxel 100 mg/m2 IV Qweek (wk) and Bevacizumab 10 mg/kg IV Q2wks x 24 weeks. Patients free of progression at 24 wks began maintenance therapy with bevacizumab 10 mg/kg IV Q2wks and erlotinib 150 mg po daily until progression with radiographic assessment every 8 wks. Primary objective was PFS with secondary objectives of response rate, overall survival (OS) and safety. All eligible patients were included in the analysis of PFS and OS. Response was evaluated among patients with measurable disease by RECIST 1.1 with central review. Patients with inadequate disease assessments were coded as non-responders. Kaplan-Meier method was used to estimate PFS and OS with patients censored at date of last tumor assessment (PFS) or date of last follow up (OS).

Results: From April 2009 – December 2015, 58 patients (median age 54, range 33-83) were enrolled; 56 (97%) had measurable disease, and all had metastatic TNBC by local assessment. 33 (57%) patients completed induction; 22 (38%) came off study during induction; 3 (5%) continue on maintenance therapy. 4 patients discontinued therapy prior to first assessment. As of June 8, 2016, 53 patients (91%) have progressed. Median follow up for surviving patients is 14.5 months (range 4.1-65.4). Median PFS is 7.7 months (95% CI 5.7, 9.5). Of 56 patients with measurable disease, 38 (66%) had partial response (PR); 10 (17%) with stable disease for clinical benefit rate (CBR) of 86%. Median OS is 18.2 months (95% CI 16.3, 24.5). Most common grade 3-4 toxicities during induction were neutropenia [17 (29%), 1 grade 4], fatigue [13 (22%), all grade 3], leukopenia [7 (12%), all grade 3], and neuropathy [7 (12%), all grade 3]. Rash was most common ≥ grade 3 toxicity during maintenance [4 (7%), grade 3]. One patient experienced clinical CHF during maintenance month 16 requiring bevacizumab discontinuation. Conclusions: Nab-paclitaxel and bevacizumab followed by maintenance targeted therapy with bevacizumab and erlotinib was well tolerated. While the observed PFS did not meet pre-specified criteria of interest, the majority of patients experienced clinical benefit (86%) with 30 (57%) receiving maintenance targeted therapy. Correlative studies are ongoing. Supported by Genentech (OSI4266s), Celegene (AX-CL-BRST-PI-003828) and Janssen.

Citation Format: Specht JM, Gadi VK, Gralow JR, Korde LA, Linden HM, Salazar LG, Rodler ET, Cundy A, Buening BJ, Baker KK, Redman MW, Kurland BF, Garrison MA, Smith JC, vanHaelst C, Anderson JE. Combined targeted therapies for advanced triple negative breast cancer: A phase II trial of nab-paclitaxel and bevacizumab followed by maintenance targeted therapy with bevacizumab and erlotinib [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 P4-22-11.

Abstract P5-13-07: An investigator-initiated registry trial of simple oral therapy for low risk breast cancer

Background: Across multiple studies performed in several countries with widely instituted screening mammography programs at different intervals between exams, up to 19% of breast cancer identified is in patients whose disease would otherwise go undetected and not have caused any ill effect if left untreated. Recent advances in pathologic and multigene assays have demonstrated promise to better identify low risk breast cancer and appropriately tailor treatments. Nonetheless, most women who may have such low-risk, estrogen receptor expressing lesions continue to be offered only an aggressive treatment paradigm. This most commonly includes surgery and lymph node evaluation and, in the case of breast conservation, breast irradiation following surgery, with the option of endocrine therapy for 5-10 years.

Trial design: We propose a multi-center US registry study of post-menopausal, female breast cancer patients age 60 and older who will be managed 5 years with oral endocrine therapy for mammographically screen-detected, node-negative, unifocal invasive disease with low clinical grade, high estrogen/progesterone receptor expression, negative Her2 expression, Ki67 rate &lt;20%, and low-risk multigene expression analysis with Mammaprint Breast Cancer Recurrence Assay. Target lesions will be confirmed with a pre-treatment bilateral breast MRI and imaged routinely with standard mammography or ultrasound at 3-month intervals during months 1-36 and at 6-month intervals during months 37-60 to assess for disease response. Enrolled patients will have an ECOG performance status of 0-2. Medication history will be documented at routine follow-up visits.

Our primary objective will be to determine the frequency of conversion from a low-toxicity approach with oral endocrine therapy to conventional care with surgery +/- radiation therapy as a result of progression of disease or patient/provider choice. Progression of disease will be quantified objectively as &gt;20% growth of the target lesion as compared to baseline in imaging measurements. After 5 years of endocrine therapy sans disease progression, patients may elect to continue or stop treatment or convert to standard care.

Statistical methods: We will determine the conversion rate from oral therapy for any cause to conventional management (compliance). Compared to the most pessimistic assumed true-rate for compliance of 0.5, we predict &gt;90% power to detect a decrease of 0.1 in outcomes with an alpha of 5% (corresponds to a 95% Confidence Interval). Using descriptive statistics, we will also quantify for disease responses and progression-free survival. Our sample size will be ample for multiple sub-analyses including measurement of differences emanating from tertiary care versus local oncologic management, advanced imaging outcomes (if performed on any subset of patients), effect of type of endocrine therapy type (SERM vs AI), and effect of age and/or comorbidity severity interaction.

Accrual: Clinic sites with large patient cohorts are now being selected nationwide to enroll and manage patients' disease with endocrine treatment only. We will select up to 20 sites and enroll 300 patients with low-risk disease.

Citation Format: Gadi VK, Preusse C, Calhoun KE, Kim J, Linden HM, Rendi M, Etzioni RB, Gooley T, Lyman G, Stork L, van der Baan B, Barth N, Rahbar H. An investigator-initiated registry trial of simple oral therapy for low risk breast cancer. [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 P5-13-07.

Abstract P3-07-34: Breast cancer pathologic subtype and fetal microchimerism

Background: Stably persistent offspring-origin cells in a woman’s circulation and tissues decades after pregnancy, also known as fetal microchimerism, is deficient in women with biologically unselected breast cancer and suggests a protective role. Although the finding is in harmony with the well-known association of parity with protection against future breast cancer, it has recently emerged that certain tumor types such as triple negative breast cancer are positively associated with parity. Here we tested the hypothesis that fetal microchimerism is positively associated with triple negative breast cancer in young women.

Methods: Buffy coat specimens were obtained from a subset (n=450) of pathologically confirmed low-risk luminal and high-risk triple negative breast cancer patients and control participants from a population-based cohort study of all women aged 20-44 diagnosed with invasive breast cancer in the three county Seattle-Puget Sound metropolitan area from 2004-2010. Using quantitative PCR, DNA extracts from these specimens were tested for the presence and concentration of Y chromosome sequence DYS14, a marker of male fetal microchimerism.

Results: At this interim analysis of 405 specimens, 29.3% (56/191) of the healthy controls tested positive. Using controls as a reference group, 37.8% (34/90; OR .68; 95% CI .39-1.2) of women who developed luminal breast cancer tested positive for the presence of DYS14, while 26.6% (33/124; OR 1.14; 95% CI .67-1.96) of women who developed triple negative breast cancer tested positive.

Discussion: A preliminary analysis does not suggest an association between fetal microchimerism and breast cancer pathologic subtype in young women. Additional analyses are pending and will be presented at the meeting. Young women may regulate fetal microchimerism differently and surprisingly our data may suggest that as fetal microchimerism emerges later in life in the circulation, so does the protection against breast cancer – a finding consistent with population based studies of parity as a risk factor for breast cancer.

Citation Format: David A Mahoney, Veronica L Winget, VK Gadi, Christopher I Li, Peggy L Porter, Jean A McDougall. Breast cancer pathologic subtype and fetal microchimerism [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P3-07-34.

Abstract P4-08-01: Assessing the safety and feasibility of efficient hypothesis testing in patients with metastatic triple negative breast cancer

We hypothesize that new insights into how cancers progress and respond to treatment will come from clinical trials that i) extensively characterize the molecular features of a patient’s cancer; ii) use results to predict drug susceptibilities; iii) treat in accordance with these predictions; and iv) learn from individual patient outcomes to iterate and improve over time. To investigate the feasibility of this type of clinical study, we launched the "Intensive Trial of OMics in Cancer" (ITOMIC) for patients with metastatic triple negative breast cancer (TNBC) (Clinicaltrials.gov ID: NCT01957514). Eligible patients have metastatic TNBC, are platinum-naive, and are scheduled to receive Cisplatin. Biopsies are performed under carefully controlled conditions prior to Cisplatin – starting all subjects on a common treatment path, and uncoupling the time needed for specimen analysis from immediate therapy. Biopsies are repeated upon completion of Cisplatin and following subsequent therapies. A subset of specimens is chosen for whole Exome Sequencing, deep sequencing of a panel of cancer associated genes, and RNA-sequencing. De-identified results are placed on a web-based server for analysis and discussed at a meeting of the ITOMIC tumor board. A report describing results and potential therapies is provided to the subject’s oncologist. Treatment decisions are left to the discretion of the oncologist. If a decision is taken to pursue treatments identified in our report we offer assistance in accessing those treatments.

Ten patients have been screened and seven have enrolled. Subjects range in age from 40 to 77 years and all but one has received extensive prior treatment for metastatic TNBC. All seven underwent an initial set of biopsies, targeting between two and five metastatic sites. For most metastatic sites, multiple core needle passes are performed. All subjects tolerated the biopsies well without significant adverse events, and all started treatment with Cisplatin. Three subjects completed Cisplatin and underwent a second round of biopsies.

Potential targets for therapy were identified in 5 of the first 6 subjects, and three subjects have received four predicted therapies: 1) a patient with somatic loss of BRCA1 and two linked FGFR2 activating mutations, who was treated first with Veliparib through a single-patient IND and then switched to Ponatinib which produced a partial response; 2) a patient with a novel missense ROS1 mutation treated with crizotinib; and 3) a patient with CYP3A4 copy gain treated with cyclophosphamide.

Conclusion: Our early experience indicates that this approach is feasible and may increase the efficiency of learning from patients with advanced cancer.

Citation Format: C Anthony Blau, Colin Pritchard, Michael O Dorschner, Sibel Blau, Brigham Mecham, Elisabeth Mahen, VK Gadi, Wayne Monsky, Kimberly Burton, Arturo Ramirez, Jackie Stilwell, Eric Kladjian, Carol Collins, Jeannine S McCune, William S Noble, Julie Gralow, Frank Senecal, Linda Dhaene, Nicole Kuderer, Jennifer Specht, Chaozhong Song, Carla Grandori, Nathan Price, Mary Goldman, Aime Radenbaugh, David Haussler, Jingchun Zhu. Assessing the safety and feasibility of efficient hypothesis testing in patients with metastatic triple negative breast cancer [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P4-08-01.

In situ breast cancer and microchimerism

Microchimeric cells of fetal origin persistent in the maternal circulation post-partum are associated with protection against invasive breast cancer. Here using quantitative genomic methods, we evaluated for the presence of male fetal microchimerism in buffy coat cells from women with a prior history of breast carcinomas in situ (CIS) and in healthy controls. Fetal microchimerism was detected in 75 of 88 controls (85%) and in 57 of 89 CIS patients (64%). The odds ratio for protection against non-invasive breast disease was 0.26 (95% confidence interval 0.12-0.56; p < 0.001 adjusted for age and body mass index). Similar to women with invasive breast cancer, women with CIS who are naturally at high risk for future invasive disease were deficient for fetal microchimerism. In addition to autologous anti-tumor immune responses, the maintenance of haploidentical microchimerism may impart an allogeneic edge in immunosurveillance.

A phase 2 study of 16α-[18F]-fluoro-17β-estradiol positron emission tomography (FES-PET) as a marker of hormone sensitivity in metastatic breast cancer (MBC)

PURPOSE

16α-[(18)F]-fluoro-17β-estradiol positron emission tomography (FES-PET) quantifies estrogen receptor (ER) expression in tumors and may provide diagnostic benefit.

PROCEDURES

Women with newly diagnosed metastatic breast cancer (MBC) from an ER-positive primary tumor were imaged before starting endocrine therapy. FES uptake was evaluated qualitatively and quantitatively, and associated with response and with ER expression.

RESULTS

Nineteen patients underwent FES imaging. Fifteen had a biopsy of a metastasis and 15 were evaluable for response. Five patients had quantitatively low FES uptake, six had at least one site of qualitatively FES-negative disease. All patients with an ER-negative biopsy had both low uptake and at least one site of FES-negative disease. Of response-evaluable patients, 2/2 with low FES standard uptake value tumors had progressive disease within 6 months, as did 2/3 with qualitatively FES-negative tumors.

CONCLUSIONS

Low/absent FES uptake correlates with lack of ER expression. FES-positron emission tomography can help identify patients with endocrine resistant disease and safely measures ER in MBC.

Abstract P4-01-03: HDACi (vorinostat) in metastatic breast cancer to restore sensitivity to ER-directed (AI) therapy: A phase II clinical trial with FES imaging correlates

Background: Histone deacetylase inhibitors (HDACi) have shown pre-clinical promise in estrogen receptor(ER)-modulation and restoring sensitivity to endocrine manipulation, suggesting potential clinical benefit (Sabnis 2011) (Huang 2000) in ER+ breast cancer. Vorinostat is an FDA-approved HDACi for CTCL, and could have a beneficial role in restoring ER-signaling in endocrine-resistant tumors (Munster 2011) (Yardley 2011). [F-18]fluoroestradiol (FES) PET imaging may be used to monitor regional tumor ER expression in patients with breast cancer (Linden 2011).

Methods: Patients with metastatic breast cancer with prior clinical benefit from endocrine manipulation who progressed on an AI therapy are eligible for this ongoing trial. In part A, patients were given vorinostat for 2 weeks, then resumed AI for 6 W. In part B (reflecting results of prior HDACi trials) patients are given vorinostat 400mg po daily 5/7 days 3/4 weeks while AI is given continuously. Paired FES and FDG PET are performed at baseline, week 2 and 8; clinical/radiologic assessment of disease is also performed at week 8. Patients with clinical benefit (response or stable disease) may continue on treatment until progressive disease or study withdrawal. Lesion-level analysis of the association between baseline FES uptake (logged) and FES/FDG ratio used generalized estimating equations (GEE) with small-sample adjustments to standard errors.

Results: 12/ 20 planned patients have accrued, and the treatment is well tolerated. Enrolled women were postmenopausal, the majority with primary infiltrating ductal tumors, bone/soft tissue dominant with longstanding metastatic disease, exposed to multiple endocrine and chemotherapy regimens. Five patients have had clinical benefit (2/4 on part B with greater HDACi exposure). One patient withdrew from the study due to toxicity. FES and FDG uptake was analyzed in 42 lesions in 11 patients. Average FES uptake was 2.0 (SULmean) for patients with clinical benefit, and 1.2 in patients with progressive disease by 8 weeks (p = 0.09). FES/FDG ratio at baseline was also associated with response (p = 0.04).

Conclusions: HDACi therapy is promising in relapsed ER+ breast cancer. Imaging of metabolic pathways in parallel with clinical trials may accelerate understanding of the underlying tumor biology and refine treatment selection.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P4-01-03.

Abstract P3-08-11: Pregnancy after breast cancer and recurrence risk

Background: Several retrospective studies report an improved overall (and possibly disease-free) survival of women who become pregnant following breast cancer diagnosis compared to women who choose not to or are unable to become pregnant. The objective of the current study is to evaluate associations with breast cancer biologic and stage characteristics from the baseline tumor with different recurrence outcomes in women with and without a pregnancy subsequent to their cancer diagnosis.

Methods: From a population-based cohort study of all women aged 20-44 diagnosed with invasive breast cancer in the three county Seattle-Puget Sound metropolitan area, we conducted a secondary recontact interview. Recontact information included cancer recurrence and obstetric history, including all pregnancies occurring after breast cancer diagnosis. Univariate associations were evaluated using chi square. A time-to-event analysis was conducted, evaluating the relationship between pregnancy and recurrence, with consideration of stage and tumor type (triple negative tumor or not) as confounders.

Results: At this interim, an approximately 70% response rate for the re-contact study was achieved, yielding data from 458 women overall. Excluding 8 women who were pregnant at the time of their breast cancer diagnosis, 450 were available for analysis. Of these, 13 (2.9%) became pregnant at least once after their breast cancer diagnosis. Among women with complete pathologic information available (n = 274), those with a pregnancy subsequent to their cancer diagnosis had triple negative tumor types more often than those who did not have a subsequent pregnancy (4/8, 50% vs. 44/266, 17%, p = 0.03). Tumor stage did not differ between women with and without a subsequent pregnancy. Overall, 30 total cancer recurrences were captured in the re-contacted cohort; none of these occurred among women with subsequent pregnancy (0/13, 0% vs. 30/437, 6.9% among women without subsequent pregnancy), p = 0.3. For 448/450 women with complete information on timing of recurrence, a time-to-event analysis adjusting for tumor type did not show a significant association between subsequent pregnancy and recurrence risk, p = 0.14 by Likelihood Ratio test.

Conclusions: In this population, breast cancer recurrence risk was not increased among women with a pregnancy subsequent to their cancer diagnosis. Despite the more common triple negative tumor type among the group of women with subsequent pregnancy, none of these women experienced a cancer recurrence. Our study adds to a substantial literature suggesting that pregnancy after breast cancer does not appear to have a detrimental effect on disease recurrence. The relationship between tumor type and its potential influence on both decision-making regarding pregnancy and the biology of pregnancy as it relates to breast cancer recurrence merits further investigation.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P3-08-11.

Abstract P4-01-02: The role of FLT PET early assessment of response to endocrine therapy for early stage breast cancer

Background: In estrogen receptor positive (ER+) tumors, a low proliferative index (Ki-67) two weeks into endocrine therapy predicts response. FLT PET non-invasively measures tumor proliferation in vivo. The pre-operative window is an opportunity to assess impact of systemic therapies. We tested associations between FLT PET qualitative and quantitative measures and Ki-67 following two weeks of aromatase inhibitor (AI) therapy.

Methods: Women with clinical stage I-II ER+ HER2– breast cancer underwent “run-in” of AI monotherapy prior to definitive surgery. Premenopausal women were given GNRH agonist treatment 2 W prior to AI therapy. FLT PET was performed before AI therapy, and 1-7 days before surgery. Ki-67 was measured in baseline core biopsy and surgical specimens.

Results: Fourteen patients (8 postmenopausal, 6 premenopausal) have been enrolled. All have undergone baseline FLT PET imaging; 11 have completed imaging and surgery, including one premenopausal patient with no residual invasive carcinoma following 26 days of AI therapy. The majority harbored ductal carcinomas (n = 9, 5 with lobular histology) with the majority histologic grade ≥ 2 (n = 11). The median number of days exposed to AI was 19 (range, 9-42). Baseline SUVmax ranged from 1.2 to 3.9 (median 2.2), and post run-in SUV (6-64 days later) ranged from 1.2 to 2.8 (median 1.8). Baseline Ki-67 ranged from 6-26.2, median 11.6; surgical Ki-67 post AI therapy ranged from 0- 20.3 median 3.7, with seven below 5%. SUV and flux declined in most patients, as did Ki-67.

Quantitative FLT flux correlated with tumor response assessed by proliferative index (Ki-67) before the “run-in” period, with a stronger correlation at surgery, Pearson correlation coefficients = 0.41 and 0.82, respectively. FLT SUV and qualitative changes were not strongly associated with Ki-67.

Conclusions: Both pre and postmenopausal women with early stage breast cancer showed imaging and tissue response to endocrine therapy. Quantitative, but not qualitative FLT is a promising tool to assess tumor proliferation and response to therapy. Accrual is ongoing and updated results will be reported.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P4-01-02.

Acquisition of the rheumatoid arthritis HLA shared epitope through microchimerism

OBJECTIVE

HLA-DRB1 alleles associated with risk of rheumatoid arthritis (RA) encode similar HLA-DRB1 sequences, called the shared epitope (SE). The most common SE sequences are QKRAA and QRRAA. Nevertheless, a substantial number of RA patients lack the SE. Bidirectional fetal-maternal trafficking results in long-term persistence of fetal cells in the mother and maternal cells in her offspring, a process known as microchimerism. This study was undertaken to discover whether RA patients who lack the SE can acquire it through microchimerism.

METHODS

We studied a total of 86 female subjects who were genotypically negative for the SE, comprising 52 patients with RA and 34 healthy controls. We developed specific real-time quantitative polymerase chain reaction assays for the SE-encoded sequences QKRAA and QRRAA, and used them to test DNA extracted from peripheral blood mononuclear cells.

RESULTS

Microchimerism with the SE was found significantly more often in RA patients than controls (odds ratio 4.1 [95% confidence interval 1.6-10.0], P = 0.003). Concentrations of SE microchimerism were also significantly higher among RA patients than controls (P = 0.002). In separate analyses for SE type, the prevalence of QKRAA microchimerism in RA patients versus healthy controls was 17% versus 3% (9 of 52 versus 1 of 34; P = 0.03) and the prevalence of QRRAA microchimerism was 40% versus 18% (21 of 52 versus 6 of 34; P = 0.04), respectively. Microchimerism concentrations were also higher in RA patients than healthy subjects for QKRAA (P = 0.03) and QRRAA (P = 0.03).

CONCLUSION

These results indicate that RA patients who genotypically lack the SE can acquire the SE as persistent microchimerism from fetal-maternal cell exchange, suggesting that SE-encoding microchimerism could be a risk factor for RA.

Prospective assessment of fetal-maternal cell transfer in miscarriage and pregnancy termination

BACKGROUND

Fetal cells (microchimerism) are acquired by women during pregnancy. Fetal microchimerism persists decades later and includes cells with pluripotent capacity. Persistent microchimerism has the capacity for both beneficial and detrimental maternal health consequences. Both miscarriage and termination of pregnancy can result in fetal microchimerism. We sought to determine whether cellular fetal microchimerism is acquired during management of pregnancy loss and further explored factors that could influence fetal cell transfer, including viability of fetal tissue, surgical versus medical management and gestational age.

METHODS

Pregnant women (n= 150 samples from 75 women) with singleton pregnancies undergoing a TOP (n= 63) or treatment for embryonic or fetal demise (miscarriage, n= 12) were enrolled. Mononuclear cells were isolated from blood samples drawn before, and 30 min after, treatment. Fetal cellular microchimerism concentrations were determined using quantitative PCR for a Y chromosome-specific sequence, expressed as genome equivalents of fetal DNA per 100 000 maternal cell equivalents (gEq/10(5)). Detection rate ratios were determined according to clinical characteristics.

RESULTS

Cellular fetal microchimerism was found more often in post- compared with pretreatment samples, 24 versus 5% (P= 0.004) and at higher concentrations, 0-36 versus 0-0.7 gEq/10(5) (P< 0.001). Likelihood of microchimerism was higher in surgical than medical management, detection rate ratio 24.7 (P= 0.02). The detection rate ratio for TOP versus miscarriage was 16.7 for known male fetuses (P= 0.02). Microchimerism did not vary with gestational age.

CONCLUSIONS

Significant fetal cell transfer occurs during miscarriage and TOP. Exploratory analyses support relationships between obstetric clinical factors and acquisition of fetal cellular microchimerism; however, our limited sample size precludes definitive analysis of these relationships, and confirmation is needed. In addition, the long-term persistence and potential consequences of fetal microchimerism on maternal health merit further investigation.

P1-17-04: Phase I Study of PARP Inhibitor ABT-888 (Veliparib) in Combination with Cisplatin and Vinorelbine for Patients with Advanced Triple Negative Breast Cancer and/or BRCA-Mutation Associated Breast Cancer

Background: Inhibitors of poly(ADP-ribose) polymerase (PARP) have shown preclinical and clinical activity in targeting tumors with pre-existing DNA repair defects, in particular BRCA1 and BRCA2 deficient tumors. Cisplatin (CP) has demonstrated synergy with ABT-888 (veliparib) in breast cancer xenograft models and has anti-tumor activity in triple negative (TN) and BRCA-1 deficient breast cancer. Vinorelbine (V) combined with CP has shown safety and efficacy in patients with pretreated metastatic breast cancer.

Methods: We are conducting a phase I study to determine the maximum tolerated dose (MTD), pharmacokinetic (PK) and pharmacodynamic profiles (PD), and preliminary anti-tumor activity of veliparib in combination with CP and V in patients (pts) with metastatic breast cancer who are either TN or who have BRCA1 or BRCA2 mutation associated breast cancer. Cohorts receive escalating doses of ABT-888 orally BID days 1–14, CP 75 mg/m2 intravenously (IV) day 1 and V 25 mg/m2 IV days 1,8 every 21 days, in a 3+3 design.

Results: As of 6/14/11, 18 eligible female pts have been enrolled. The median age at registration was 50 years (range 34–78 years). Sixteen pts received at least one prior metastatic regimen (range 0–8). Three pts had previously treated brain metastases. BRCA mutation status was as follows: BRCA1+ (3 pts); BRCA2+ (2 pts); confirmed mutation negative (8 pts); unknown (5 pts). Four pts received the 20 mg BID veliparib dose (one patient in the cohort died of progressive disease early in cycle 1 and was replaced), 3 received 30 mg BID, 6 received 40 mg BID, and 5 have been enrolled at dose level 4 (60 mg BID). Dose limiting toxicities occurred in one patient at the 40 mg BID dose (grade 4 thrombocytopenia), and one patient at the 60 mg BID dose (grade 3 neutropenic fever). Adverse events are typical for a platinum-based chemotherapy regimen and include nausea, fatigue, thrombocytopenia, and neutropenia. MTD has not been reached. Of 11 pts evaluable for radiographic response to date, 6 (55%) had a PR (3 of whom have a BRCA mutation) and 5 (45%) had stable disease. Correlative studies will use immunohistochemistry and gene expression array to evaluate the profile of TN breast cancer and predictors of response to treatment.

Conclusion: Veliparib in combination with CP and V has been generally well tolerated to date. Objective anti-tumor activity was seen in BRCA mutation carriers and in pts with sporadic TN breast cancer. PK, PD, and biomarker analysis is underway. Enrollment continues in the dose escalation cohorts.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P1-17-04.

P1-06-25: Changes in FDG PET SUV Correlates with Ki-67 Following 2 Weeks of Aromatase Inhibitor Therapy in ER+ Early Stage Breast Cancer, a Pilot Imaging Study

Background: In estrogen receptor positive (ER+) tumors, a low proliferative index (Ki-67) two weeks into endocrine therapy predicts response. FDG PET non-invasively measures tumor sites in vivo. The pre-operative window is an opportunity to assess impact of systemic therapies. We tested associations between FDG PET standardized uptake value (SUV) and Ki-67 after two weeks of aromatase inhibitor (AI) therapy in newly diagnosed, postmenopausal women.

Methods: Postmenopausal patients with clinical stage I-II ER+ HER2− primary tumors underwent a 9–35 day “run-in” of AI monotherapy prior to definitive surgery. FDG PET was performed before AI therapy, and 1–5 days before surgery. Ki-67 was measured in baseline core biopsy and surgical specimens.

Results: To date, 18 patients (median age 59) have been enrolled of whom 14 patients have undergone serial FDG PET imaging with 12 completed assessment of Ki-67 in surgical samples including one who had no residual invasive carcinoma. The majority harbored ductal carcinomas (n=16) with 10/18 having histologic grade ≥ 2. The median number of days exposed to AI was 18 (range, 9–35). Baseline SUV ranged from 1.8 to 10.9 (median 2.5), and post run-in SUV (7-34 days later) ranged from 1.0 to 10.7 (median 2.5). A median 14% decrease in SUV was observed between paired FDG PET studies (range, 44% decline to 13% increase). Five of 12 patients’ index lesion FDG SUV declined by 20% or more; all also had Ki-67 ≤5% at surgery. An additional 5 patients with Ki-67 ≤5% at surgery had percentage change in FDG PET SUV of 0% to 17% decline. Results will be updated as accrual is ongoing.

Conclusions: Substantial changes in FDG PET SUV in the breast tumor were appreciated early in AI therapy. SUV declined or was stable in all but one patient of 14, and all patients with ≥ 20% decrease in SUV had a low (≤5%) Ki-67 at surgery. Serial PET is a promising measure of early response to therapy.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P1-06-25.

P1-09-09: Fetal Microchimerism and In Situ Breast Cancer

Background: Haploidentical fetal cells acquired and maintained by a woman in her blood and tissues long after pregnancy completion, also known as fetal microchimerism, is inversely associated with invasive breast cancer. Furthermore, in healthy women, absence of fetal microchimerism serves as a risk factor for development of future breast cancer (J Clin Oncol 29: 2011 suppl; abstr 1574). Here, we test the hypothesis that failure to maintain fetal microchimerism following pregnancy is also associated with in situ breast cancer.

Methods: Buffy coat specimens were obtained from the Roswell Park Cancer Institute Data Bank and BioRepository from parous patients with in situ breast cancer and parous control volunteers with no prior history of cancer. Using quantitative PCR, DNA extracts from peripheral blood buffy coat specimens were tested by a single female operator blinded to case:control status for the presence (and concentrations) of Y chromosome sequence DYS14, a marker of male fetal microchimerism.

Results: In this interim analysis, 83% (34/41) of healthy control women and 55% (29/53) in situ breast cancer patients tested positively for the presence of DYS14. The unadjusted odds ratio was 0.25 (95%-CI of 0.08−0.72; p=0.008). Median concentrations were also greater in healthy women compared to women with in situ cancer, 0.15 versus 0.02 fetal cell equivalents per 10^5 proband genomes, respectively (p=0.004).

Summary: Preliminary results suggest that the associations of fetal microchimerism and in situ breast cancer are similar in magnitude and direction to that observed for invasive disease. The natural history of in situ breast cancer is for a large portion of patients to develop invasive disease in 8–10 years absent of comprehensive locoregional control; results here point to a failure to maintain or loss of haploidentical fetal cells well before development of invasive disease. Final results from the entire cohort planned (n=200) with adjustment for anthropometric, reproductive, and cancer specific factors will be presented at the meeting.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P1-09-09.

P2-09-09: Dynamic FDG PET and DCE-MRI To Assess Tumor Metabolism and Blood Flow in Response to Neoadjuvant Sunitinib and Paclitaxel Followed by AC + G-CSF in Patients with Locally-Advanced (LABC) and/or Inflammatory Breast Cancer (IBC)

Background

Kinetic analysis of FDG PET and DCE-MRI can identify patterns of breast tumor metabolism and perfusion that predict pathologic response, relapse, and survival in patients (pts) receiving neoadjuvant chemotherapy (NC). We are enrolling pts with LABC or IBC on a phase II trial of neoadjuvant sunitinib and metronomic chemotherapy. The addition of sunitinib, a tyrosine kinase inhibitor of VEGFR1-3, PDGFR, c-KIT, to NC is hypothesized to increase rate of pathologic complete response (pCR). Assessment of FDG PET measures of glucose metabolism (Ki), glucose delivery (K1) which approximates blood flow, and MRI measures of blood flow and vascularity (peak enhancement (PE), signal enhancement ratio (SER), and volume) during NC offers the opportunity to evaluate the in vivo pharmacodynamics of sunitinib.

Methods: Pts with HER2−negative LABC or IBC participated in a companion imaging trial with [18F]-FDG PET and DCE-MRI before NC (T0), after a 1 wk run-in of sunitinib 25 mg po daily (T1), after 12 wks of paclitaxel 80 mg/m2 IV Qwk and sunitinib 25 mg po daily (T2), and prior to breast surgery (T3) after 15 wks of doxorubicin 24 mg/m2 IV Qwk, cyclophosphamide 60 mg/m2 po daily with G-CSF 5 mcg/kg SC days 2–6 each wk. FDG metabolic rate (Ki), glucose delivery (K1), and MR indices (PE, SER, volume) were assessed. Imaging parameters were compared for groups defined by NC pathologic complete response (pCR) vs. non-pCR using a two-sample t-test.

Results: The imaging trial included 14 pts. Median age was 50 years (43-79). All had HER2−negative LABC (n=13, 93%) or IBC (n=1, 7%). Most tumors were ductal (n=12, 86%) and high grade (n=9, 64%). Seven (50%) tumors were ER negative. pCR was observed in 4/14 (29%) pts in this cohort. Changes in Ki, K1, and MRI volume were observed between baseline (T0) and the sunitinib run-in (T1). For example, 8/14 (57%) had a decrease in K1 of &gt;20%, and 3 (21%) had an increase of ≥20%. These 1 week changes did not predict subsequent response to NC. However, declines in Ki and K1 between baseline (T0) and following sunitinib and paclitaxel (T2) did predict pCR. The average change in glucose metabolism (Ki) was a 95% decline with pCR and a 68% decline otherwise (p= 0.007). The average T0-T2 K1 change was 83% decline for pts with pCR and 47% decline otherwise (p= 0.029). In contrast to our previous studies in LABC pts treated with NC where decline in K1 was predictive of response, decline in Ki appears to be the more robust predictor of response in this cohort. Of 11 pts with PET scans at T2 and T3, 5 showed marked increase (&gt;20%) in Ki and 6 showed marked increase in K1 after withdrawal of sunitinib.

Conclusion: Changes in breast tumor glucose metabolism (Ki), glucose delivery (K1), and blood flow (MR PE, SER, volume) can be detected after 1 wk of sunitinib, but are not predictive of response to NC. In the setting of anti-vascular therapy, measures of tumor glucose metabolism (Ki) are predictive and perhaps, more predictive of outcome than measures of glucose delivery (K1) which may be altered by sunitinib.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P2-09-09.

Antibiotic-mediated chemoprotection enhances adaptation of E. coli PNP for herpes simplex virus-based glioma therapy

The E. coli PNP suicide gene sensitizes solid tumors to nucleoside prodrugs, such as 6-methylpurine-2'-deoxyriboside (MeP-dR). In this study using lentiviral, MuLv, and HSV-based gene transfer, we quantified thresholds for inhibition of tumor growth and bystander killing by E. coli PNP and tested the role of intestinal flora in this process. Regressions of human glioma tumors following retroviral transduction exhibited dose dependence on both the level of PNP expression and the dose of MeP-dR administered, including strong tumor inhibition when 90-99% bystander cells comprised the tumor mass. A replication competent, non-neurovirulent herpes simplex virus (HSV) deficient in both copies of the gamma-1 34.5 gene was next engineered to express E. coli PNP under the egr-1 promoter (HSV-PNP). HSV-PNP injected intratumorally (17 million pfu/0.05 ml) in nude mice bearing 300 mg human glioma flank tumors produced a delay in tumor growth (approximately 24 days delay to one doubling). MeP-dR treatment after antibiotic therapy (to eliminate enteric flora encoding PNP enzymes) resulted in antitumor enhancement, with arrest of tumor growth (delay to doubling >50 days). Bystander killing of the magnitude described here has been difficult to accomplish with other suicide genes, such as HSV-tk or cytosine deaminase. The results establish a model for applying E. coli PNP to HSV treatment of glioma.

In vivo sensitization of ovarian tumors to chemotherapy by expression of E. coli purine nucleoside phosphorylase in a small fraction of cells

This report examines a major barrier to suicide gene therapy in cancer and other diseases: namely, bystander cell killing. Existing vectors for in vivo gene delivery are inefficient and often transduce or transfect less than 1% of target cells. The E. coli PNP gene brings about cellular necrosis under conditions when 1 in 100 to 1 in 1000 cells express the gene product in vitro. In vivo bystander killing at or near this magnitude has not been reported previously. In the present experiments, transfection of cells with the E. coli PNP gene controlled by a SV40 promoter resulted in 30 nmol 6-methyl purine deoxyriboside (MeP-dR) converted per milligram tumor cell extract per hour (or conversion units (CU)). This level of expression led to elimination of entire populations of tumor cells in vitro after treatment with MeP-dR. Much earlier killing was observed using a tat transactivated E. coli PNP vector (approximately seven-fold higher activity, 230 CU). In vivo effects on tumor growth were next examined. Human ovarian tumors transfected with E. coli PNP were excised 5 days after i.p. implantation from the peritoneal cavities of mice in order to determine both E. coli PNP enzymatic activity and the fraction of cells expressing the gene. PNP activity at 5 days after gene transfer was approximately 170 CU and was expressed in approximately 0.1% of the tumor cells as judged by in situ hybridization. The expression of E. coli PNP at this level produced a 30% increase in life span (P < 0.001) and 49% reduction in tumor size (P < 0.005) after MeP-dR treatment, as compared with control tumors. Our observations lead to the conclusion that pronounced bystander killing by E. coli PNP is conferred in vivo, and that vectors capable of transgene expression in as few as one in 1000 cells can produce substantial antitumor effects if expression on a per cell basis is very high.

Components of human papillomavirus that activate transcription and support plasmid replication in human airway cells

Human papillomaviruses (HPVs) such as types 6 and 11 can establish lifelong infections in airway epithelial cells in patients, and long-term infection can lead to pulmonary involvement and death. The mechanisms underlying this persistence depend on both the transcriptional activity of the viral enhancers and promoters and the ability of this virus to maintain its double-stranded circular DNA genome in infected tissues. We investigated the transcription and replication properties of HPV sequence elements and protein products in a human airway cell line. We showed that incorporation of the upstream regulatory region and cotransfection with expression vectors of two virus-encoded proteins, E1 and E2, conferred approximately 5,000-fold stimulation of reporter gene expression. Transient plasmid replication in transfected human airway cells and lungs of FVB/N-C57BL/6 mice was demonstrated by a modified transient replication assay. These results have important implications for viral pathogenesis in airway cells and the potential of HPV-based replicons for gene transfer into airway epithelium.

Gene therapy of cancer: activation of nucleoside prodrugs with E. coli purine nucleoside phosphorylase

During the last few years, many gene therapy strategies have been developed for various disease targets. The development of anticancer gene therapy strategies to selectively generate cytotoxic nucleoside or nucleotide analogs is an attractive goal. One such approach involves the delivery of herpes simplex virus thymidine kinase followed by the acyclic nucleoside analog ganciclovir. We have developed another gene therapy methodology for the treatment of cancer that has several significant attributes. Specifically, our approach involves the delivery of E. coli purine nucleoside phosphorylase, followed by treatment with a relatively non-toxic nucleoside prodrug that is cleaved by the enzyme to a toxic compound. This presentation describes the concept, details our search for suitable prodrugs, and summarizes the current biological data.

Bystander killing of melanoma cells using the human tyrosinase promoter to express the Escherichia coli purine nucleoside phosphorylase gene

We used a gene transfer-based system to generate highly toxic purine bases in tumor cells transfected with the Escherichia coli purine nucleoside phosphorylase (PNP) gene. Because these toxic purines are membrane permeant, they mediate effective killing of neighboring cells that do not express E. coli PNP ("bystander" toxicity). In mixed cultures containing increasing percentages of cells with gene expression, 100% cancer cell growth arrest and total population killing was demonstrated when as few as 1-2% of cells expressed E. coli PNP. We used E. coli PNP to test bystander killing of human melanoma cells. A 529-bp region upstream of the human tyrosinase gene start site was shown to direct melanoma-specific expression in human cell lines. When this human tyrosinase regulatory region was used to control E. coli PNP expression, profound toxicity was observed in melanoma cells after treatment with the relatively nontoxic substrate 6-methylpurine-deoxyriboside, which is converted by E. coli PNP into the highly toxic purine base 6-methylpurine. Bystander toxicity was estimated as at least 100 cells killed for each cell expressing E. coli PNP, a level substantially higher than that of other tumor sensitization genes currently being used in clinical trails. These results suggest that the high bystander activity of the system could lead to significant antimelanoma responses in vivo.