A Tale of Two Hospitals: Effect of Access to Care Through a Safety Net Hospital on Adjuvant Therapy, Imaging Compliance and 5-Year Survival Rates Compared to the University Hospital Served by the Same Breast Cancer Clinical Teams

RATIONALE AND OBJECTIVES

To compare rates of guideline-concordant care, imaging surveillance, recurrence and survival outcomes between a safety-net (SNH) and tertiary-care University Hospital (UH) served by the same breast cancer clinical teams.

MATERIALS AND METHODS

647 women with newly diagnosed breast cancer treated in affiliated SNH and UH between 11.1.2014 and 3.31.2017 were reviewed. Patient demographics, completion of guideline-concordant adjuvant chemotherapy, radiation and hormonal therapy were recorded. Two multivariable logistic regression models were performed to investigate the effect of hospital and race on cancer stage. Kaplan-Meier log-rank and Cox-regression were used to analyze five-year recurrence-free (RFS) and overall survival (OS) between hospitals and races, (p < 0.05 significant).

RESULTS

Patients in SNH were younger (mean SNH 53.2 vs UH 57.9, p < 0.001) and had higher rates of cT3/T4 disease (SNH 19% vs UH 5.5%, p < 0.001). Patients in the UH had higher rates of bilateral mastectomy (SNH 17.6% vs UH 40.1% p < 0.001) while there was no difference in the positive surgical margin rate (SNH 5.0% vs UH 7.6%, p = 0.20), completion of adjuvant radiation (SNH 96.9% vs UH 98.7%, p = 0.2) and endocrine therapy (SNH 60.8% vs UH 66.2%, p = 0.20). SNH patients were less compliant with mammography surveillance (SNH 64.1% vs UH 75.1%, p = 0.02) and adjuvant chemotherapy (SNH 79.1% vs UH 96.3%, p < 0.01). RFS was lower in the SNH (SNH 54 months vs UH 57 months, HR 1.90, 95% CI: 1.18-3.94, p = 0.01) while OS was not significantly different (SNH 90.5% vs UH 94.2%, HR 1.78, 95% CI: 0.97-3.26, p = 0.06).

CONCLUSION

In patients experiencing health care disparities, having access to guideline-concordant care through SNH resulted in non-inferior OS to those in tertiary-care UH.

Mapping Cellular Interactions from Spatially Resolved Transcriptomics Data

Cell-cell communication (CCC) is essential to how life forms and functions. However, accurate, high-throughput mapping of how expression of all genes in one cell affects expression of all genes in another cell is made possible only recently, through the introduction of spatially resolved transcriptomics technologies (SRTs), especially those that achieve single cell resolution. However, significant challenges remain to analyze such highly complex data properly. Here, we introduce a Bayesian multi-instance learning framework, spacia, to detect CCCs from data generated by SRTs, by uniquely exploiting their spatial modality. We highlight spacia's power to overcome fundamental limitations of popular analytical tools for inference of CCCs, including losing single-cell resolution, limited to ligand-receptor relationships and prior interaction databases, high false positive rates, and most importantly the lack of consideration of the multiple-sender-to-one-receiver paradigm. We evaluated the fitness of spacia for all three commercialized single cell resolution ST technologies: MERSCOPE/Vizgen, CosMx/Nanostring, and Xenium/10X. Spacia unveiled how endothelial cells, fibroblasts and B cells in the tumor microenvironment contribute to Epithelial-Mesenchymal Transition and lineage plasticity in prostate cancer cells. We deployed spacia in a set of pan-cancer datasets and showed that B cells also participate in PDL1/PD1 signaling in tumors. We demonstrated that a CD8+ T cell/PDL1 effectiveness signature derived from spacia analyses is associated with patient survival and response to immune checkpoint inhibitor treatments in 3,354 patients. We revealed differential spatial interaction patterns between γδ T cells and liver hepatocytes in healthy and cancerous contexts. Overall, spacia represents a notable step in advancing quantitative theories of cellular communications.

Neratinib + fulvestrant + trastuzumab for HR-positive, HER2-negative, HER2-mutant metastatic breast cancer: outcomes and biomarker analysis from the SUMMIT trial

BACKGROUND

HER2 mutations are targetable alterations in patients with hormone receptor-positive (HR+) metastatic breast cancer (MBC). In the SUMMIT basket study, patients with HER2-mutant MBC received neratinib monotherapy, neratinib + fulvestrant, or neratinib + fulvestrant + trastuzumab (N + F + T). We report results from 71 patients with HR+, HER2-mutant MBC, including 21 (seven in each arm) from a randomized substudy of fulvestrant versus fulvestrant + trastuzumab (F + T) versus N + F + T.

PATIENTS AND METHODS

Patients with HR+ HER2-negative MBC with activating HER2 mutation(s) and prior cyclin-dependent kinase 4/6 inhibitor (CDK4/6i) therapy received N + F + T (oral neratinib 240 mg/day with loperamide prophylaxis, intramuscular fulvestrant 500 mg on days 1, 15, and 29 of cycle 1 then q4w, intravenous trastuzumab 8 mg/kg then 6 mg/kg q3w) or F + T or fulvestrant alone. Those whose disease progressed on F + T or fulvestrant could cross-over to N + F + T. Efficacy endpoints included investigator-assessed objective response rate (ORR), clinical benefit rate (RECIST v1.1), duration of response, and progression-free survival (PFS). Plasma and/or formalin-fixed paraffin-embedded tissue samples were collected at baseline; plasma was collected during and at end of treatment. Extracted DNA was analyzed by next-generation sequencing.

RESULTS

ORR for 57 N + F + T-treated patients was 39% [95% confidence interval (CI) 26% to 52%); median PFS was 8.3 months (95% CI 6.0-15.1 months). No responses occurred in fulvestrant- or F + T-treated patients; responses in patients crossing over to N + F + T supported the requirement for neratinib in the triplet. Responses were observed in patients with ductal and lobular histology, 1 or ≥1 HER2 mutations, and co-occurring HER3 mutations. Longitudinal circulating tumor DNA sequencing revealed acquisition of additional HER2 alterations, and mutations in genes including PIK3CA, enabling further precision targeting and possible re-response.

CONCLUSIONS

The benefit of N + F + T for HR+ HER2-mutant MBC after progression on CDK4/6is is clinically meaningful and, based on this study, N + F + T has been included in the National Comprehensive Cancer Network treatment guidelines. SUMMIT has improved our understanding of the translational implications of targeting HER2 mutations with neratinib-based therapy.

Aspirin use is associated with improvement in distant metastases outcome in patients with residual disease after neoadjuvant chemotherapy

PURPOSE

Aspirin (ASA) use has been correlated with improved outcomes in high-risk patients at risk for distant metastases. Breast cancer (BC) patients with residual disease, particularly nodal disease (ypN +) after neoadjuvant chemotherapy (NAC), are high-risk patients portending worse outcomes. We hypothesized that ASA use can reduce distant metastases and improve outcomes in these patients.

METHODS

Patients at our institutions from 2005 to 2018, with BC who did not achieve complete response (pCR) after NAC were reviewed (IRB protocol STU- 052012-019). Data, including evidence of ASA use, and clinico-pathologic parameters were analyzed. Survival outcomes were obtained (Kaplan Meier analysis) and univariate (UVA) and multivariable (MVA) Cox proportional hazards regression analyses were performed.

RESULTS

637 did not achieve pCR (ypN+ = 422). 138 were ASA users. Median follow-up for the control and ASA group were 3.8 (IQR 2.2-6.3) and 3.8 (IQR 2.5-6.4) years, respectively. Majority were stage II/III. 387 were hormone receptor positive, 191 HER2 +, and 157 triple negative. On UVA, ASA use, PR status, pathologic and clinical stage showed significance for DMFS, and disease-free survival (DFS). On MVA, ASA use associated with improved 5-year DFS (p = .01, 87.0% vs 79.6%, adjusted HR = 0.48) and improved 5-year DMFS (p = .04, 92.8% vs 89.2%, adjusted HR = 0.57). In the ypN + patients, ASA use associated with improved 5-year DMFS (p = .008, 85.7% vs 70.7%, adjusted HR = 0.43) and DFS (p = .02, 86.8% vs 74.3%, adjusted HR = 0.48).

CONCLUSION

For non-responders, particularly ypN + patients, ASA use associated with improved outcome. These hypotheses-generating results suggest for development of prospective clinical trials of augmented ASA use in selected very high-risk BC patients.

Abstract OT2-17-01: Phase 1 trial of anthracycline chemotherapy in combination with CD40 agonist and Flt3 ligand in metastatic triple-negative breast cancer

Background: Only a subset of patients with metastatic triple-negative breast cancers (TNBC) demonstrate response to FDA approved PD-1 immune checkpoint blockade (ICB), and few have durable responses. Data suggests that breast cancers have defects in antigen presentation and that antigen presenting cells especially the DC1 subtype of dendritic cells (DCs) are required for response to ICB. CD40 agonists activate antigen presenting cells including DCs and B cells and also repolarize macrophages to an anti-tumor phenotype. Flt3 ligand is a growth factor that increases differentiation and expansion of DCs. We recently demonstrated in pre-clinical TNBC models that the combination of liposomal-doxorubicin chemotherapy, a CD40 agonist, and a Flt3 ligand improves outcomes compared to alternate combinations. Methods: This is a single arm phase I pilot study of liposomal-doxorubicin, CDX-1140 (CD40 agonist), and CDX-301 (Flt3 ligand) combination therapy in patients with metastatic or unresectable locally advanced metastatic TNBC. Patients will be randomized to 3 lead-in arms (triplet therapy, doublet immunotherapy only, or liposomal-doxorubicin only) for 1 cycle prior to receiving triplet therapy with fresh tissue biopsies before and after the lead-in treatment. CDX-301 will be discontinued after 2 cycles; liposomal-doxorubicin and CDX-1140 will be continued until disease progression or clinically limiting toxicities. Primary endpoint is determination of a recommended phase 2 dose based on treatment-related adverse events including dose-limiting toxicities. Secondary endpoints include anti-tumor immune response after triplet therapy, after immunotherapy alone, and after liposomal-doxorubicin alone; median progression-free survival, overall response rate, duration of response, and clinical benefit rate. Key eligibility criteria are unresectable stage III or stage IV TNBC (ER ≤10%, PR ≤10%, HER2/neu negative), 1st to 3rd line metastatic treatment setting (1st line patients need to be PD-L1 negative by 22C3 assay), measurable disease by RECIST 1.1 criteria, consent for pre-treatment and on-treatment biopsies of amenable soft tissue tumor lesions, no prior treatment with an anti-CD40 antibody or a Flt3 ligand, no anthracycline treatment in the metastatic setting, no prior progression while on anthracycline-based therapy or within 6 months of completing neoadjuvant chemotherapy, and no history of non-infectious pneumonitis or current pneumonitis. This trial will enroll up to 45 patients across multiple sites (NCT05029999).

Citation Format: Sangeetha Reddy, Meredith Carter, Isaac Chan, Nisha Unni, Namrata Peswani, Dawn Klemow, Samira Syed, Shahbano Shakeel, Farjana Fattah, Chul Ahn, Yisheng Fang, Heather McArthur, Nicole Sinclair, Michael Yellin, Denise Yardley, Nan Chen, Joyce O’Shaughnessy, Rita Nanda, Suzanne D. Conzen, Carlos Arteaga. Phase 1 trial of anthracycline chemotherapy in combination with CD40 agonist and Flt3 ligand in metastatic triple-negative breast cancer [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr OT2-17-01.

The Utility of Breast Cancer Index (BCI) Over Clinical Prognostic Tools for Predicting the Need for Extended Endocrine Therapy: A Safety Net Hospital Experience

INTRODUCTION

Extended endocrine therapy (EET) benefits select patients with early-stage hormone-receptor positive (HR+) breast cancer (BC) but also incurs side effects and cost. The Clinical Treatment Score at Five Years (CTS5) is a free tool that estimates risks of late relapse in estrogen-receptor positive (ER+) BC using clinicopathologic factors. The Breast Cancer Index (BCI) incorporates 2 genomic assays to estimate late relapse risk and likelihood of benefit from EET. This retrospective study assesses the utility of BCI in selecting EET candidates in a safety net hospital.

MATERIALS AND METHODS

We performed a retrospective chart review on 69 women with early-stage HR+, HER2- BC diagnosed at our institution from December 2009 to February 2016 on whom BCI was submitted. The CTS5 score was also calculated to assess clinical risk of late relapse.

RESULTS

Median age was 53 years. All patients included in our analysis had early ER+ HER2-negative BC. Roughly half of the patients (55%) were postmenopausal and 61% were of Hispanic origin. A total of 34 patients (49%) were deemed high-risk (>5%) for late relapse by CTS5, compared to 42 (61%) by BCI. BCI identified 31 (45%) patients that would benefit from EET and of those, 74%% were advised EET. 16 (47%) clinical high-risk patients were advised against EET due to low benefit predicted by BCI. In the clinical low risk group, 9 (26%) were recommended EET based on high benefit predicted by BCI.

CONCLUSION

BCI is reasonable to consider in early-stage HR+ BC and offered clinically relevant information over clinical pathologic information alone.

Improving participation of under-represented minorities in breast cancer therapeutic trials in a safety-net system

90

Background: Racial and ethnic minorities remain under-represented in cancer clinical trials. Strategies to improve access and participation of diverse populations in clinical trials is therefore a key step to improve outcomes and eliminate disparities. Methods: Parkland Health (PH) is the safety-net system for Dallas County, Texas, and is affiliated with the UT Southwestern/Harold C. Simmons Comprehensive Cancer Center (SCCC). Trial operations at PH is mainly supported by a dedicated team of SCCC research coordinators. Interventions employed to increase minority access and accruals were focused on optimizing the portfolio, increasing provider awareness, and enhanced screening. A bilingual research patient navigator was also added to the research team to improve patient education and engagement. Transportation and childcare assistance are routinely provided for patients at PH. Accrual data for 2021, compared to 2017-2020, is presented here. Results: The majority (73%) of breast cancer patients at PH are uninsured and 88% belong to racial/ethnic minorities (57% Hispanics, 31% Blacks). Of the 15 therapeutic breast cancer trials open at SCCC in 2021, 12 (80%) were open at PH. The PH breast cancer trial portfolio included 4 cooperative group, 5 industry-sponsored (ISTs), and 3 investigator-initiated studies (IITs). Four trials were in metastatic setting and 8 were in curative intent setting. Four trials required a genomic biomarker. Forty-three patients were enrolled in therapeutic trials at PH in 2021. This represents 10.3% (43/418) of new cases during the same time period. Thirty-two were enrolled in cooperative group studies, 10 in IITs, and 1 in ISTs. The majority (93%) of the trial participants belonged to under-represented minorities. Number of trial participants in 2021 increased by 48% compared to the best year in the past 5 years (29 patients enrolled in 2018). Conclusions: Collaboration between academic institutions and safety-net systems presents a unique opportunity to provide clinical trial options to under-represented minorities. In this setting, interventions to improve trial portfolio, provider awareness, screening process, and patient education, as well as addition of a patient research navigator resulted in a significant increase in the number of minority participants in breast cancer trials at our safety-net hospital.

Reasons for declining participation in breast cancer trials among minorities at a safety-net health system

95

Background: Despite increasing awareness, racial and ethnic minorities remain under-represented in clinical trials. Understanding patients’ reasons to decline participation can help tailor solutions to improve minority enrollment in cancer trials. Methods: Parkland Health (Dallas County, TX) is a safety-net health system, and affiliated with the UT Southwestern/Harold C. Simmons Comprehensive Cancer Center (SCCC). Over 80% of the breast cancer patients treated at Parkland belong to racial and ethnic minorities. Potential study candidates are referred to the clinical trial support team, which includes a Hispanic bilingual patient navigator. Patients who decline to participate are asked to describe their reasons. Data for screening and accrual to therapeutic breast cancer trials at Parkland between January 2021 and May 2022 is presented here. Results: A total of 193 potential study candidates were referred to the trial support team in the pre-screening phase. Ninety-five patients (49%) were excluded after screening (screen-fails). Of the 98 patients who met all study specific eligibility criteria, 93% belonged to minorities: 69% (68/98) Hispanics and 23% (23/98) Blacks. Thirty-one patients (32%) declined participation in clinical trials. Compared to Hispanics, Black patients were more likely to decline participation: Blacks 65% (15/23) vs Hispanics 19% (13/68); p < 0.0001. Patients' reasons for declining to participate in trials included: lack of interest (14/31), excessive trial requirements such as extra biopsies (8/31), and potential delay in treatment due to additional tests (5/31). Four patients declined participation in a de-escalation trial due to the fear of inferior outcomes with less treatment. Among patients who declined participation, 53% of Blacks and 23% of Hispanics cited lack of interest as the reason (p = NS). Conclusions: We observed a higher participation rate among Hispanics, which may in part reflect the impact of having a bilingual research navigator from the same ethnic background. Lack of interest was a major reason to decline, particularly among Blacks. Strategies focused on patient education and trust are being implemented to further improve minority participation in trials at our institution.

Neratinib plus fulvestrant plus trastzuzumab (N+F+T) for hormone receptor-positive (HR+), HER2-negative, HER2-mutant metastatic breast cancer (MBC): Outcomes and biomarker analysis from the SUMMIT trial

1028

Background: N is an oral, irreversible pan-HER TKI with activity against HER2 mutations. Genomic analyses from the SUMMIT MBC cohort following N±F suggest that resistance to N may occur via mutant allele amplification or secondary HER2 mutations. Adding T to N+F in SUMMIT showed encouraging durable responses in patients (pts) with HR+, HER2-mutant MBC and prior CDK4/6 inhibitors (CDK4/6i). Methods: SUMMIT (NCT01953926) enrolled pts with HR+, HER2-negative MBC with activating HER2 mutation(s) and prior CDK4/6i. Pts received N+F+T (oral N 240 mg/d with loperamide prophylaxis, im F 500 mg d1&15 of cycle 1 then q4w, iv T 8 mg/kg initially then 6 mg/kg q3w). During the small, randomized portion of the trial, pts received N+F+T, F+T or F (1:1:1 ratio). Pts randomized to F+T or F could crossover to N+F+T at progression. Efficacy endpoints: investigator-assessed ORR and CBR (RECIST v1.1); DOR; best overall response. Pre-treatment tumor tissue was centrally assessed retrospectively by next-generation sequencing. ctDNA from patient samples was assessed by NGS. Results: SUMMIT has completed enrolment; we report efficacy from 45 pts in the N+F+T cohort, plus 10 pts who progressed on F (n=6) or F+T (n=4) and crossed over to N+F+T (Table). HER2 allelic variants in the 45 N+F+T pts and ORR (%) (pts may have >1 mutation) were: V777L (n=6, 50%), L755S/P (n=15, 40%), S310F (n=4, 50%), exon 20 insertion (n=11, 36%), other KD missense (n=6, 33%), TMD missense (n=2, 0%), exon 19 deletion (n=1, 0%). Conclusions: N+F+T is a promising combination for HR+, HER2-mutated MBC with prior exposure to CDK4/6i, across a range of activating HER2 mutations. Results from the upcoming Apr 2022 data cut, including biomarkers, safety, mechanisms of acquired resistance, and preclinical mechanism of N+T, will be presented. Clinical trial information: NCT01953926. [Table: see text]

Phase 1 pilot study with dose expansion of chemotherapy in combination with CD40 agonist and Flt3 ligand in metastatic triple-negative breast cancer

TPS1126

Background: Only a subset of patients with metastatic triple-negative breast cancer demonstrate response to currently approved PD-1 immune checkpoint blockade, and few have durable responses. Antigen presentation defects may be a reason for this low response because deficiency of antigen-presenting DC1 dendritic cells is associated with poor anti-tumor immunity. CD40 agonists are a class of agents that activate antigen presenting cells including dendritic cells and B cells and also repolarize macrophages. Flt3 ligand is a growth factor that increases dendritic cells. In line with this, we recently demonstrated in pre-clinical models that the combination of liposomal-doxorubicin chemotherapy, a CD40 agonist, and a Flt3 ligand improves outcomes of breast cancer compared to alternate combinations. Methods: This is a single arm phase I pilot study of liposomal-doxorubicin, CDX-1140 (CD40 agonist), and CDX-301 (Flt3 ligand) combination therapy in patients with metastatic or unresectable locally advanced metastatic triple-negative breast cancer. Patients will be randomized to 3 lead-in arms (triplet therapy, doublet immunotherapy only, liposomal-doxorubicin only) prior to receiving full triplet therapy with fresh tissue biopsies before and after the lead-in treatment. CDX-301 will be discontinued after 2 cycles; liposomal-doxorubicin and CDX-1140 will be continued until disease progression or clinically limiting toxicities. Primary endpoint is determination of a recommended phase 2 dose based on treatment-related adverse events including dose-limiting toxicities. Secondary endpoints include anti-tumor immune response after triplet therapy, after immunotherapy alone, and after liposomal-doxorubicin alone; median progression-free survival, overall response rate, duration of response, and clinical benefit rate. Key eligibility criteria are unresectable stage III or stage IV triple-negative breast cancer (ER ≤10%, PR ≤10%, HER2/neu negative), 1st to 3rd line metastatic treatment setting (1st line patients need to be PD-L1 negative by 22C3 assay), measurable disease by RECIST 1.1 criteria, consent for pre-treatment and on-treatment biopsies of amenable soft tissue tumor lesions, no prior treatment with an anti-CD40 antibody or a Flt3 ligand, no anthracycline treatment in the metastatic setting, no prior progression while on anthracycline-based therapy or within 6 months of completing neoadjuvant chemotherapy, and no history of non-infectious pneumonitis or current pneumonitis. This trial will enroll up to 45 patients across multiple sites. Clinical trial information: NCT05029999.

Abstract PD2-01: A platform of CDK4/6 inhibitor-resistant patient-derived breast cancer organoids illuminates mechanisms of resistance and therapeutic vulnerabilities

CDK4/6 inhibitors (CDK4/6i) in combination with antiestrogens have revolutionized the treatment of ER+ metastatic breast cancer (MBC), significantly prolonging survival. However, this combination is not curative, and tumors eventually acquire resistance. Following progression on this combination, patients are left with limited treatment options. A diverse array of mechanisms of resistance to CDK4/6i + antiestrogens have been described. However, laboratory models that capture this heterogeneity of resistance mechanisms are lacking. Patient-derived organoids (PDOs) provide a rapid, robust and reliable platform that recapitulates intra-tumor heterogeneity, partially mimics the cancer microenvironment, and accurately predicts drug response. We aspired to generate a platform of CDK4/6i-resistant breast cancer PDOs to serve as models for understanding acquired resistance to CDK4/6i + antiestrogens and identifying therapies to overcome resistance. We successfully established 16 PDOs out of 32 biopsies (50% efficiency) of metastates from patients with ER+ MBC progressing on CDK4/6i (palbociclib or abemaciclib) + antiestrogens (letrozole or fulvestrant; median response to combination = 9 months). Our collection includes PDOs derived from lobular (n=3) and inflammatory (n=2) breast cancers and reflects racial/ethnic diversity (50% white/not Hispanic; 18.8% Hispanic; 12.5% Black; 12.5% other/unknown). Next-gen sequencing reports were available for 10 patients from which organoids were established, revealing alterations associated with CDK4/6i and/or antiestrogen resistance, including ESR1 (n=2), HER2/ERBB2 (n=2), PTEN (n=2), CCNE1 (n=1), NF1 (n=1), and ARID1A (n=1). Furthermore, one biopsy and its derived organoid lost ER expression, and 5 harbored PIK3CA activating mutations. Thus far, we have performed targeted DNA-sequencing on 7 PDOs and found 13/15 (86.7%) concordance with driver mutations from tumor NGS reports. PDOs established from CDK4/6i-resistant biopsies maintained resistance to palbociclib or abemaciclib ± fulvestrant (500 nM each) in 3D cell viability assays (6 days of treatment). In contrast, control PDOs established from primary ER+ breast cancer surgical samples (n=2) were sensitive to each CDK4/6i ± fulvestrant (median viability for combination=25.6-31.5% for control vs 65.2-80.5% for resistant). GSEA analysis of RNA-seq data from control (n=2) and CDK4/6i-resistant (n=6) PDOs cultured in estrogen-depleted media ± 200 nM palbociclib revealed that palbociclib treatment resulted in downregulation of E2F target and G2M checkpoint signatures in control but not resistant PDOs. Next, we performed a high-throughput screen of 1,000 compounds in 3 resistant PDOs. One PDO showed exquisite sensitivity to G2/M cell cycle checkpoint components, including CDK1, PLK1, Aurora kinase, ATR, Chk1, and Wee1 inhibitors. Finally, treatment of 10 resistant PDOs with the CDK2/4/6 inhibitor PF-06873600 revealed that the CCNE1 (cyclin E1)-amplified PDO was highly sensitive (IC50=130 nM vs &gt;1000 nM), supporting that CCNE1-amplified tumors are vulnerable to CDK2 inhibition. Conclusions: PDOs can be successfully established from ER+ MBC biopsies, maintain the resistant phenotype in culture, retain driver alterations found in tumors from which they were derived, and fail to suppress E2F targets following treatment with CDK4/6i. Therefore, these PDOs represent valuable models to understand and explore diverse mechanisms of CDK4/6i resistance and therapeutic vulnerabilities.

Citation Format: Ariella B. Hanker, Sumanta Chatterjee, Yunguan Wang, Dan Ye, Dhivya R. Sudhan, Brian M. Larsen, Lauren C. Smith, Yilin Zhang, Vishal Kandagatla, Kuntal Majmudar, Ezequiel Renzulli, Saurabh Mendiratta, Kimberly Blackwell, Alana L. Welm, Sunati Sahoo, Nisha Unni, Cheryl M. Lewis, Tao Wang, Ameen A. Salahudeen, Carlos L. Arteaga. A platform of CDK4/6 inhibitor-resistant patient-derived breast cancer organoids illuminates mechanisms of resistance and therapeutic vulnerabilities [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 PD2-01.

Abstract P1-18-35: Futibatinib in combination with fulvestrant in patients with metastatic breast cancer (MBC) harboring high-level FGFR1 amplification: Preliminary data from a phase 2 study

Background: FGFR gene amplifications are found in 18% of breast cancers (BCs), with FGFR1 amplifications occurring in ≈10% of cases, predominantly in hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2−) MBCs. FGFR1 amplifications are associated with resistance to endocrine therapy, and in preclinical experiments, FGFR pathway inhibition has been shown to overcome resistance to hormone therapy in BC harboring FGFR1 amplifications. Futibatinib, a highly selective, irreversible FGFR1-4 inhibitor, has shown preclinical activity in BC xenograft models harboring FGFR1/2 amplifications. In a phase 1 study, futibatinib showed promising clinical activity and tolerability across tumor types, including MBC, harboring various FGFR aberrations. A multicohort phase 2 trial (FOENIX-MBC2; NCT04024436) was designed to evaluate futibatinib alone (cohorts 1-3) or in combination with fulvestrant (cohort 4) in patients with MBC harboring FGFR2 or FGFR1 amplifications, respectively. Here, we report preliminary safety data from cohort 4 of FOENIX-MBC2, including data from a safety lead-in. Methods: Cohort 4 of FOENIX-MBC2 enrolled adult patients with HR+ HER2− MBC harboring high levels of FGFR1 amplification (FGFR1:CEN8 ratio ≥5 or FGFR1 copy number ≥10 signals per cell), Eastern Cooperative Oncology Group performance status 0-1, and adequate organ function. Patients were fulvestrant naive and had previously received 1-2 endocrine-containing therapies, ≤1 chemotherapy regimen, and a CDK4/6 inhibitor (if eligible). Cohort 4 began with a safety lead-in to assess dose-limiting toxicities (DLTs) during the first treatment cycle. Patients received oral futibatinib 20 mg once daily continuously, and intramuscular fulvestrant 500 mg was administered on days 1 and 15 of cycle 1 and day 1 of every subsequent 28-day cycle. Patients were treated until disease progression, unacceptable toxicity, or another discontinuation criterion was met. Results: As of data cutoff (March 31, 2021), cohort 4 had enrolled 8 female patients with HR+ HER2− MBC harboring high-level FGFR1 amplification. The median age was 55.5 years (range: 31-62 years), and all patients had received ≥2 prior therapies for advanced/metastatic BC. The median duration of treatment was 8.0 weeks (range: 3.0-32.7 weeks); 3 of 8 patients (38%) were continuing treatment at time of data cutoff. All patients experienced treatment-related adverse events (TRAEs; grade ≥3: 25%). The most common TRAE was hyperphosphatemia (88%), followed by constipation (62%), transaminase elevation (50%), dry mouth (38%), and alopecia (38%). Among these TRAEs, grade ≥3 events were only reported for hyperphosphatemia (12%), and no serious adverse events were reported. In this cohort, TRAEs led to dose reductions in 4 patients, dosing interruptions in 3 patients, and treatment discontinuation in 1 patient; no patients died due to TRAEs. DLTs were evaluated in 5 patients following 1 treatment cycle (1 patient was enrolled after data cutoff, and 4 of 9 patients were not evaluable for DLTs); DLTs were not experienced by any of the 5 evaluable patients. Conclusions: Based on these preliminary safety results, the combination of futibatinib and fulvestrant appears to be safe and tolerable in patients with HR+ HER− MBC harboring high-level FGFR1 amplification. The safety profile was consistent with the individual profiles of both drugs, and the treatment combination did not appear to result in synergistic toxicity. As no DLTs were observed in 5 evaluable patients, the recommended futibatinib dose in combination with fulvestrant is 20 mg once daily. Efficacy will be evaluated in the complete 28-patient post-lead-in cohort, in which enrollment is ongoing.

Citation Format: Senthil Damodaran, Nisha Unni, Karthik V. Giridhar, Brooke Daniel, Sacha Howell, Luis Costa, Marta Ferreira, Masashi Shimura, Gareth Tomlinson, Maciej Gil, Nicholas Turner. Futibatinib in combination with fulvestrant in patients with metastatic breast cancer (MBC) harboring high-level FGFR1 amplification: Preliminary data from a phase 2 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 P1-18-35.

Clinicopathological Features and Outcomes in Individuals with Breast Cancer and ATM, CHEK2, or PALB2 Mutations

INTRODUCTION

The moderate-penetrance germline mutations ATM, CHEK2, and PALB2 are implicated in an increased risk of the development of breast cancer. Whether these mutations provide clinical utility to guide treatment strategies and prognosis remains unknown.

METHODS

A retrospective case-control study from a tertiary institution compared patients with stage 0-III breast cancer, and positive for ATM, CHEK2, or PALB2 mutations, with a matched cohort selected by randomization and negative for mutations. Data acquisition included demographics, histopathologic, treatment, and clinical outcome variables.

RESULTS

A total of 145 patients with breast cancer (144 female and 1 male) were analyzed-74 mutation-positive patients (24 ATM, 26 CHEK2, 24 PALB2) and 71 mutation-negative patients. Mutation-positive patients compared with mutation-negative patients had increased family history of breast cancer (79.7 vs. 52.9%, p < 0.001) and tumor size > 2.0 cm (63.1% vs. 42.3%, p = 0.015). Patients with prior knowledge of mutational status were more likely to proceed with total mastectomy and prophylactic mastectomy (74.5% vs. 25.5%, p < 0.02; and 65.5% vs. 34.5%, p < 0.001, respectively). The unadjusted recurrence rate was higher in mutation-positive patients compared with mutation-negative patients (24.3 vs. 8.5%, p = 0.01), although mutation status was not predictive for recurrence in Cox regression analysis.

CONCLUSIONS

Patients positive for ATM, CHEK2, or PALB2 mutations had increased tumor size and were more likely to undergo extensive surgeries. Mutation status was not predictive of recurrence, although this lack of effect may have been mitigated by lower rates of recurrence in those who pursued total mastectomy. Further studies are needed to confirm these findings.

The Changing Paradigm for the Treatment of HER2-Positive Breast Cancer

For decades, HER2-positive breast cancer was associated with poor outcomes and higher mortality rates than other breast cancer subtypes. However, the advent of Trastuzumab (Herceptin) has significantly changed the treatment paradigm of patients afflicted with HER2-positive breast cancer. The discovery of newer HER2-targeted therapies, such as Pertuzumab (Perjeta), has further added to the armamentarium of treating HER2-positive breast cancers. This review highlights recent advancements in the treatment of HER2-positive diseases, including the newer HER2-targeted therapies and immunotherapies in clinical trials, which have paved (and will further update) the way for clinical practice, and become part of the standard of care in the neoadjuvant, adjuvant or metastatic setting.

Abstract P2-09-01: Clinicopathological features and surgical management trends in individuals with breast cancer and deleterious mutations in moderate penetrance genes

Background: Moderate penetrance genes - ATM, CHEK2, and PALB2 - are often included in hereditary cancer panel testing as mutations have been linked to familial breast cancer. Limited data exists on breast cancer presentation and surgical management. We aimed to review clinicopathological features of breast cancers in patients affected by these mutations and trends in surgical management compared to unaffected cancer patients. Methods: We conducted a retrospective review of breast cancer patients, stage 0 to III, with deleterious mutations in ATM, CHEK2, and PALB2 between 2007 and 2017 at a tertiary institution. Data collected included demographics, clinicopathological tumor features, and type of treatment. These patients were compared to a control group of sporadic breast cancer patients referred for genetic counseling who tested negative for deleterious mutations via panel testing. Chi-square test, t-test, and stepwise logistic regression were used for statistical analysis. Results: A total of 145 patients had breast cancer (144 women and 1 male). There were 74 mutation-positive patients (24 ATM, 26 CHEK2, 24 PALB2) and 71 mutation-negative patients (Table 1). No differences were found in age or ethnicity among both groups. Mutation-positive patients had a higher rate of family members affected by breast cancer (79.7% vs. 52.9% in mutation-negative, p=0.0006), and tumors greater than 2 cm (63.1% vs. 42.3% in mutation-negative, p=0.0152). No differences were found on tumor histopathology, use of radiotherapy, and use of chemotherapy/endocrine therapy between the two groups. Of the patients harboring mutations, 55 patients received surgical treatment for their breast cancer after discovery of their mutation status, while the rest had surgery performed prior to genetic testing. All controls received surgery as part of treatment. Significant differences were seen in type of surgery chosen in each group. There was a lower rate of breast-conserving surgery in the mutation-positive group (25.5% vs. 46.5% in mutation-negative, p=0.0155). Additionally, 65.5% of mutation-positive patients underwent contralateral prophylactic mastectomy (CPM) compared to 33.3% in mutation-negative patients (p=0.0004). There was no association between age or ethnicity and choice of CPM. Conclusions: Mutation-positive patients are more likely to have positive family histories and larger tumors at diagnosis. They also have a higher rate of mastectomy and double the rate of CPM compared to those unaffected by mutations in moderate penetrance genes. These patients opt for more radical surgical treatment despite lack of clear guidelines for this approach. Further studies are needed to better advise physicians and patients regarding treatment decisions when encountering these mutations.

Table 1. Patient, tumor, and treatment characteristicsMutationaNo mutationN=74N=71P-valueAge at diagnosis, mean (SD)48.43 (10.47)50.82 (9.84)0.1601no. (%)no. (%)EthnicityWhite49 (66.2)45 (63.4)0.8839Hispanic15 (20.3)13 (18.3)Black8 (10.8)11 (15.5)Asian2 (2.7)2 (2.8)Family history of breast cancerbYes50 (79.7)37 (52.9)0.0006No15 (20.3)33 (47.1)Stagec0 and I23 (33.8)35 (49.3)0.0644II and III45 (66.2)36 (50.7)Tumor sizec (cm)≤ 224 (36.9)41 (57.7)0.0152&gt; 241 (63.1)30 (42.3)Lymph nodecPositive24 (36.4)26 (36.6)0.9752Negative42 (63.6)45 (63.4)Nuclear gradeI9 (15.8)14 (20.0)0.8284II23 (40.4)27 (38.6)III25 (43.9)29 (41.4)Estrogen receptorPositive56 (84.8)53 (74.6)0.1390Negative10 (15.2)18 (25.4)HER2/Neu receptorPositive17 (26.2)14 (19.7)0.3715Negative48 (73.8)57 (80.3)HistologyDuctal69 (93.2)63 (88.7)0.3419Lobular5 (6.8)8 (11.3)KI-67 proliferation index≤ 2017 (34.0)22 (36.7)0.7710&gt; 2033 (66.0)38 (63.3)Use of chemotherapyYes47 (67.1)45 (63.4)0.6390No23 (32.9)26 (36.6)Adjuvant radiotherapyYes42 (59.2)40 (56.3)0.7340No29 (40.8)31 (43.7)Adjuvant endocrine therapyYes45 (65.2)53 (74.6)0.2235No24 (34.8)18 (25.4)Type of surgeryBCSd14 (25.5)33 (46.5)0.0155TMd41 (74.5)38 (53.5)Contralateral prophylactic mastectomy (CPM)CPM36 (65.5)23 (33.3)0.0004No CPM19 (34.5)46 (66.7)(a). ATM, CHEK2, PALB2, (b) First and second-degree relatives, (c) Tumor size, lymph node status, and stage assessed clinically, (d) Abbreviations: BCS = breast-conserving surgery, TM = total mastectomy

Citation Format: Colton Pence, Jordan Berg, Natalia Partain, Navid Sadeghi, Caitlin Mauer, Sara Pirzadeh-Miller, Ang Gao, Hsiao Li, Nisha Unni, Samira Syed. Clinicopathological features and surgical management trends in individuals with breast cancer and deleterious mutations in moderate penetrance genes [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 P2-09-01.

Patient familiarity with, understanding of, and preferences for clinical trial endpoints and terminology

BACKGROUND

Although there is increased attention to designing and explaining clinical trials in ways that are clinically meaningful for patients, there is limited information on patient preferences, understanding, and perceptions of this content.

METHODS

Maximum difference scaling (MaxDiff) methodology was used to develop a survey for assessing patients' understanding of 19 clinical terms and perceived importance of 9 endpoint surrogate phrases used in clinical trials and consent forms. The survey was administered electronically to individuals with metastatic breast cancer affiliated with the Metastatic Breast Cancer Alliance. Analyses were performed using Bayesian P values with statistical software.

RESULTS

Among 503 respondents, 77% had a college degree, 70% were diagnosed with metastatic disease ≥2 years before survey completion, and 77% had received ≥2 lines of systemic therapy. Less than 35% of respondents reported understanding "fairly well" the terms symptomatic progression, duration of disease control, time to treatment cessation, and endpoints. Income level and time since onset of metastatic disease correlated with comprehension. Patients who had received ≥6 lines of therapy perceived that time until serious side effects (P < .001) and time on therapy (P < .001) were more important compared with those who had received only 1 line of therapy. Positively phrased parameters were associated with increased perceived importance.

CONCLUSIONS

Even among educated, heavily pretreated patients, many commonly used clinical research terms are poorly understood. Comprehension and the perceived importance of trial endpoints vary over the course of disease. These observations may inform the design, discussion, and reporting of clinical trials.

Impact of dual anti-HER2 therapy on pathologic complete response rate in breast cancer in a minority-enriched population

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Background: The addition of pertuzumab (P) to a neoadjuvant trastuzumab (H) plus chemotherapy combination has been shown to significantly improve the pathologic complete response rate (pCR) in localized HER2+ breast cancer; however, minorities have been under-represented in these trials. Racial/ethnic disparities have also been shown to affect outcomes of cancer treatment. This study is aimed to assess the impact of neoadjuvant dual HER2-blockade in an unselected minority-enriched population. Methods: A retrospective chart review was conducted of women with stage I to III HER2+ breast cancer who received neoadjuvant treatment between 2007 and 2017 at an academic institution and its affiliated safety net health system. Data on stage, chemotherapy, race/ethnicity, site of therapy (academic vs safety net hospital), and hormone receptor status were collected. All patients underwent surgery after completion of neoadjuvant chemotherapy. pCR was defined as ypT0/is, ypN0. Chi-squared test and univariate/multivariate logistic regression were used for statistical analysis. Results: The study population included 261 women with the following race/ethnic distribution: 37.7% Non-Hispanic Whites, 34.6% Hispanics, 20.6% Blacks, and 7% other racial/ethnic origin. Ninety-five patients (36%) received chemotherapy-H vs 166 patients (64%) received chemotherapy-HP. Patients at the safety net health system had higher stage at diagnosis compared to the academic site. Site of care and race/ethnicity did not impact the choice of neoadjuvant treatment. The pCR rate was significantly higher for the chemotherapy-HP group (55.4%) compared to the chemotherapy-H group (34.7%) (p = 0.001). There was no association between race/ethnicity, or site of treatment (academic vs safety net), and the probability of achieving pCR. Multivariate analysis showed only dual anti-HER2 therapy (OR: 2.67, CI: 1.55-4.59, p = 0.0004) and hormone-receptor negative status (OR: 2.18, CI: 1.30-3.67, p = 0.0031) to correlate with pCR. Conclusions: Neoadjuvant dual anti-HER2 therapy was more likely to result in a pCR in our minority enriched population. Our data also suggests the combination of chemotherapy-HP confers similar benefit irrespective of race/ethnicity or site of care.

Growth factor use and rate of neutropenic complications in breast cancer patients treated with dose-dense paclitaxel: A 5-year experience from a safety net hospital

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Background: The NCCN guidelines recommend growth factor (G-CSF) support to reduce the risk of febrile neutropenia and maintain dose density in patients receiving dose dense chemotherapy. We retrospectively reviewed growth factor utilization with dose dense paclitaxel (ddT) in breast cancer patients treated at our institution. Methods: Electronic medical records of patients treated at Parkland Health and Hospital System between 2012-2017 for breast cancer with dose dense adriamycin and cyclophosphamide (ddAC) followed by ddT were reviewed. Data on patient characteristics as well as G-CSF use and neutropenic complications were collected. Results: Two-hundred sixty eight patients received a total of 1019 cycles of ddT. Only one physician in the practice routinely prescribed G-CSF after ddT. The majority of ddT cycles were administered without G-CSF support (781 vs 238 cycles). There were no episodes of neutropenic fever in either group. The rate of grade 3/4 neutropenia was 2.1 % with G-CSF support (all grade 3), and 2.7% without G-CSF support (85% grade 3), p = 0.61. Treatment delays were longer in patients who did not receive G-CSF support, but this difference was not statistically significant (mean of 4 vs 2.2 days, p = 0.07). The number of cycles needed to treat to prevent 1 episode of grade 3/4 neutropenia was 167. Based on Medicare average sales price (ASP) for pegfilgrastim, routine use of G-CSF in our patient population would have added over $3.6M to the cost of care over the study period. Conclusions: Our results show a similarly low rate of neutropenic complications in patients receiving dose dense paclitaxel with or without G-CSF support. Therefore routine use of G-CSF with this regimen is not warranted. Judicious use of expensive medications such as G-CSF would reduce the cost of care and financial toxicity to patients, and promote high value care.

Use of palliative care among patients with metastatic breast cancer at a safety net hospital

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Background: Palliative Care (PC) has been shown to improve quality of life in lung cancer patients, and ASCO recommends it as an adjunct to standard oncologic care. Data regarding the use of PC in other cancers and in disadvantaged populations is scant. We studied the patterns of use of PC in patients with metastatic breast cancer (MBC) at a safety net hospital. Methods: Electronic health records (EHR) of 234 patients who were diagnosed with MBC from 2010 to 2016 at Parkland Health and Hospital System (PHHS) were reviewed, and data on demographics, diagnostics, treatments, and palliative care elements were collected. Results: 105 of 234 (44.8%) patients with MBC were referred to PC, either as outpatients, inpatients, or both. The average time from the first visit with medical oncology to placement of an outpatient referral to PC was 390 days. Of the 79 patients with outpatient referrals to palliative care, we have hormone receptor status on 50. 12 of these patients had triple negative breast cancer; 30 had hormone receptor positive breast cancer. 77 (32% of all patients) patients had formal documentation of advanced directives (AD) in the EHR. Of these, 69 (89.6%) had seen PC. 133 patients have died, and 37 (27.8% of expired patients) died at the Parkland Hospital. Among the 96 patients who did not die in the hospital, 73 (76%) patients had some discussion of hospice prior to death. Conclusions: Less than half of patients with MBC at PHHS were referred to PC, and among those who are, referrals are placed late in the disease course, on average, more than one year after the first medical oncology visit. Lack of a sustained relationship with PC results in truncated goals of care discussions. As a result, most patients do not have formal documentation of AD in the EHR. Furthermore, they do not benefit from discussions with PC that could guide the management of their malignancy while they still have therapeutic options. Instead, patients discuss hospice with their providers toward the end of life, only when they are no longer candidates for cancer directed therapies. Although the use of PC resources at PHHS does not meet clinical guidelines, it is consistent with data from other studies showing inadequate use of PC resources among patients with advanced cancer.

LILRB4 signalling in leukaemia cells mediates T cell suppression and tumour infiltration

Immune checkpoint blockade therapy has been successful in treating some types of cancer but has not shown clinical benefits for treating leukaemia¹. This result suggests that leukaemia uses unique mechanisms to evade this therapy. Certain immune inhibitory receptors that are expressed by normal immune cells are also present on leukaemia cells. Whether these receptors can initiate immune-related primary signalling in tumour cells remains unknown. Here we use mouse models and human cells to show that LILRB4, an immunoreceptor tyrosine-based inhibition motif-containing receptor and a marker of monocytic leukaemia, supports tumour cell infiltration into tissues and suppresses T cell activity via a signalling pathway that involves APOE, LILRB4, SHP-2, uPAR and ARG1 in acute myeloid leukaemia (AML) cells. Deletion of LILRB4 or the use of antibodies to block LILRB4 signalling impeded AML development. Thus, LILRB4 orchestrates tumour invasion pathways in monocytic leukaemia cells by creating an immunosuppressive microenvironment. LILRB4 represents a compelling target for the treatment of monocytic AML.

Neratinib: Inching Up on the Cure Rate of HER2+ Breast Cancer?

Neratinib was recently approved by the FDA for extended adjuvant treatment of HER2⁺ breast cancer. The ExteNET trial showed improvement in invasive disease-free survival (iDFS) in the neratinib arm compared with placebo. The benefit was more pronounced in patients with estrogen receptor-positive (ER⁺)/HER2⁺ tumors, suggesting bidirectional cross-talk between the ER and HER pathways. Clin Cancer Res; 24(15); 3483-5. ©2018 AACRSee related article by Singh et al., p. 3486.