A breast cancer (BC) risk model incorporating Tyrer-Cuzick version 8 (TCv8) and a polygenic risk score (PRS) for diverse ancestries

557

Background: BC risk assessment is important for guiding personalized screening and risk-reducing interventions. TCv8 is used to estimate BC risk based on age, breast density, family cancer history and other clinical factors. Accuracy may be improved by combining TCv8 with a PRS. We developed and validated a PRS for diverse ancestries based on 149 common genetic variants (PRS-149) comprised of 56 ancestry-informative and 93 BC-associated variants. Here, we describe a BC risk model that combines PRS-149 with TCv8. Methods: Subjects had multigene panel testing for hereditary cancer and were negative for pathogenic variants in known BC susceptibility genes. A combined risk score (CRS), incorporating PRS-149 and TCv8, was developed based on 189,230 women, including 43,444 (23%) with a history of BC. Breast Imaging Reporting and Data System (BI-RADS) breast density measurements were available for 12,363 women. We used multivariable logistic regression to test breast density and PRS-149 for association with risk of BC. An independent test cohort of 6,030 BC-unaffected women with BI-RADS assessment was used to evaluate the effect of PRS-149 on risk stratification. Relative contributions of family history, breast density, other clinical factors in TCv8 and PRS-149 were examined by adding terms sequentially to an ANOVA model. We compared differences in classification of women as high (20%) or low/moderate (20%) remaining lifetime risk according to TCv8 versus CRS. Results: In the development cohort, increased breast density was significantly associated with higher risk of BC (p=3.0x10-6) with an effect size consistent with TCv8. PRS-149 improved BC risk prediction over age, breast density and family history (OR per unit standard deviation: 1.41, 95% CI: 1.37 – 1.46; p: 1.8x10-105). PRS-149 was weakly but significantly correlated with both family history (r=0.09) and breast density (r=0.01). After adjusting for multiple testing, no other factors were correlated with PRS-149. In the independent test cohort, PRS-149 explained 27% of CRS variability after accounting for family history, breast density and other clinical factors. Adding PRS-149 to TCv8 significantly altered risk estimates, with 16.3% (983/6,030) of patients classified differently by CRS versus TCv8. By TCv8 alone, 38.0% (2,289/6,030) of patients were classified as high-risk. Among patients who were high-risk by TCv8, 25.2% (576/2,289) were downgraded by CRS. Conclusions: This is the first BC risk model that includes breast density, family history, and a PRS based on genetically determined ancestry that is validated for diverse populations. Addition of PRS-149 improved risk prediction and substantially modified risk stratification compared to TCv8 alone. Implementation of CRS may therefore lead to improved identification of women who are likely to benefit from increased surveillance and preventive medications.

A descriptive study on the treatment and outcomes of patients with platinum-sensitive, advanced, BRCA- or PALB2-related pancreatic cancer who have progressed on rucaparib

4131

Background: We recently reported the results of a single arm phase II study of maintenance rucaparib in patients with platinum-sensitive advanced pancreatic cancer and a pathogenic variant in BRCA1, BRCA2, or PALB2 (NCT 03140670; Reiss, JCO 2021). However, optimal treatment following progression on PARP inhibitors (PARPi) has not been defined. Here, we report a descriptive study of post-progression treatment and outcomes of this patient population. Methods: Patients with advanced pancreatic cancer and germline or somatic BRCA1, BRCA2, or PALB2mutations treated with at least 16 weeks of platinum-based chemotherapy without progression were enrolled and treated with rucaparib until progression or unacceptable toxicity. At the time of progression, patients were treated with physician-choice chemotherapy. Here we evaluate the objective response rates (ORR) by RECIST 1.1. Overall survival (OS) and time to second progression (PFS2) calculated from trial enrollment and progression free survival on chemotherapy (PFS) by regimen were secondary endpoints. Time-to-event was analyzed by the Kaplan-Meier method and censored at date of last clinic visit, with a cutoff date of 12/10/21. Results: The trial enrolled 42 patients; 31 patients had progressed. Of these, 22 received second-line chemotherapy: nine were treated with an oxaliplatin-based regimen, nine were treated with a cisplatin-based regimen, and four were treated with non-platinum regimens. Demographics were balanced between those who received platinum versus non-platinum. All patients who received second-line chemotherapy regimens met the PFS2 endpoint and all but one patient had died at time of data cutoff. No patients had a complete response, five patients had a partial response (PR). By regimen, 1/9 patients treated with cisplatin had a PR, 3/9 treated with oxaliplatin had a PR, and 1/4 patients treated with non-platinum had a PR. OS, PFS2, PFS, and ORR results by regimen are shown in the table. Conclusions: In this small sample of patients with advanced pancreatic cancer with progressive disease on PARPi, chemotherapy retains some activity. Further study to identify predictors of response and/or resistance to post-PARPi treatment are underway. [Table: see text]

Trends in and determinants of germline BRCA1/2 testing in patients with breast and ovarian cancer

10583

Background: Germline BRCA1/2 testing (GT) is instrumental in identifying patients with breast and ovarian cancer who may be eligible for biomarker-driven poly ADP ribose polymerase inhibitor (PARPi) therapy. Little is known about recent trends and determinants of GT since PARPi were approved for these patients. Methods: We performed a retrospective cohort study of patients with breast and ovarian cancer who were eligible for GT (diagnosed with breast cancer under age 45, triple negative breast cancer under age 60, male breast cancer or ovarian cancer) between 1/2011 and 3/2020 in the nationwide Flatiron Health EHR-derived deidentified database. Duration of follow-up was at least one year for each patient. Spline regressions estimated the annual prevalence of GT within one year of diagnosis. Multivariable log binomial regressions estimated adjusted relative risks (RR) of GT by patient and tumor characteristics. Multiple imputation with chained equations was conducted for missing data. Results: Among 2,982 eligible patients with breast cancer, 1,682 (56%) underwent GT within one year of diagnosis with a median time of 42 days. GT increased from 37% in 2011 to 68% in 2020, with a significantly higher RR after PARPi were approved for breast cancer in 1/2018 (RR 1.35, 95% CI 1.20-1.51). In multivariable analyses, there were no appreciable differences by sex, race or ethnicity, but there was a negative linear relationship between GT and age (RR 0.93, 95% CI 0.90-0.96 for every 5 years). After adjusting for age, the 87 breast cancer patients with Medicare were also less likely to undergo GT despite being eligible (RR 0.67, 95% CI 0.48-0.95 vs commercial insurance). Among 5,563 eligible patients with ovarian cancer, 1,968 (35%) underwent GT within one year of diagnosis with a median time of 101 days. GT increased from 23% in 2011 to 53% in 2020, with a significantly higher RR after PARPi were approved for ovarian cancer in 12/2014 (RR 2.25, 95% CI 2.01-2.52). Although insurance status was not a significant determinant of GT in patients with ovarian cancer, older age (RR 0.95, 95% CI 0.93-0.97 for every 5 years) and Black race (RR 0.80, 95% CI 0.66-0.98 vs white race) were associated with a lower likelihood of GT in multivariable analyses. All results remained similar in pre-planned sensitivity analyses restricted to the post-PARPi approval period, limiting to patients who remained alive one year after diagnosis and using the non-imputed dataset. Conclusions: GT remains underutilized in patients with breast and ovarian cancer. Although GT has increased since PARPi were approved for this population, significant disparities by age, race and insurance status persist but differ by tumor type. This study is limited by potential misclassification due to missing GT performed outside the Flatiron Health network. Multifaceted patient-, clinician- and system-level strategies are needed to ensure that all eligible patients receive GT.

A phase 1b/2 study of the BET inhibitor ZEN-3694 in combination with talazoparib for treatment of patients with TNBC without gBRCA1/2 mutations

1023

Background: Metastatic triple negative breast cancer (mTNBC) is an aggressive and heterogeneous cancer with limited therapeutic options. PARP inhibitors (PARPi), approved to treat patients with HER2- breast cancer with a germline BRCA1/2 (gBRCA1/2) mutation, have not shown efficacy in homologous recombination repair (HRR) proficient tumors. In pre-clinical models, the BET inhibitor (BETi) ZEN-3694 sensitizes wild-type (WT) BRCA1/2 tumors to PARPi through downregulation of HRR gene expression, providing a rationale for combination therapy. We previously reported results from the Ph 1b portion of the trial evaluating the combination of ZEN-3694 plus talazoparib, in TNBC patients without gBRCA1/2 mutations; here we present results from the completed Ph 1b/2 study. Methods: A Ph 1b dose finding portion (n = 15) was followed by a single arm Ph 2 Simon 2-stage portion (n = 17+20 (37)). The primary endpoint of the Ph 1b portion of the study was safety and recommended Ph 2 dose (RP2D). The secondary endpoints were pharmacokinetics (PK), pharmacodynamics (PD), and clinical benefit rate (CBR = confirmed objective response rate (ORR) + stable disease > 16 weeks). Ph 2 measured CBR as the primary endpoint, ORR and duration of response (DOR) as key secondary endpoints. Eligibility criteria for Ph 1b included TNBC (ER/PR < 10%, HER2-), WT gBRCA1/2, and > 1 prior cytotoxic regimen for mTNBC, and in the Ph2 portion ER/PR < 1% and < 2 prior cytotoxic regimens for mTNBC. Patients were dosed daily in continuous 28 day cycles until disease progression or unacceptable toxicity. Adverse events, PK, and PD in whole blood and tissue biopsies were assessed. Response endpoints were assessed per RECIST 1.1 every 2 cycles. Results: RP2D was determined to be 48mg qd ZEN-3694 plus 0.75mg qd talazoparib. The most common AE for the Ph 1b/2 study was thrombocytopenia (TCP) (55% any grade, 34% G3/4), which was managed with dose holds and reductions. Dose intensity analysis showed average daily doses of ZEN-3694 and talazoparib could be maintained above 40mg and 0.5mg, respectively, over 8 cycles. Robust target engagement was demonstrated using BET-dependent and HRR transcripts assessed in paired tumor biopsies. Ph 2 portion of the trial met its primary endpoint with a CBR of 30% (11/37). For the Ph 1b/2 trial, investgator assessed ORR was 22% (11/50), including 2 CR, CBR was 35% (18/51) and the median DOR was 24 weeks. For the subset of TNBC at diagnosis patients (no history of HR+ disease), ORR was 32% (11/34), and CBR was 44% (15/34). Conclusions: Combination of ZEN-3694 and talazoparib demonstrated anti-cancer activity in pretreated mTNBC WT gBRCA1/2 patients. All confirmed responses were observed in TNBC at diagnosis patients, whose tumors are expected to be more sensitive to the combination due to their basal-like properties. The trial is being expanded to Ph. 2b to accrue an additional 80 TNBC at diagnosis patients. Clinical trial information: NCT03901469.

Challenges and Opportunities in Engaging Primary Care Providers in BRCA Testing: Results from the BFOR Study

PURPOSE

Engaging primary care providers (PCPs) in BRCA1/2 testing and results disclosure would increase testing access. The BRCA Founder OutReach (BFOR) study is a prospective study of BRCA1/2 founder mutation screening among individuals of Ashkenazi Jewish descent that sought to involve participants' PCPs in results disclosure. We used quantitative and qualitative methods to evaluate PCPs' perspectives, knowledge, and experience disclosing results in BFOR.

METHODS

Among PCPs nominated by BFOR participants to disclose BRCA1/2 results, we assessed the proportion agreeing to disclose. To examine PCP's perspectives, knowledge, and willingness to disclose results, we surveyed 501 nominated PCPs. To examine PCPs' experiences disclosing results in BFOR, we surveyed 101 PCPs and conducted 10 semi-structured interviews.

RESULTS

In the BFOR study overall, PCPs agreed to disclose their patient's results 40.5% of the time. Two hundred thirty-four PCPs (46.7%) responded to the initial survey. Responding PCPs were more likely to agree to disclose patients' results than non-responders (57.3% vs. 28.6%, p<0.001). Among all respondents, most felt very (19.7%) or somewhat (39.1%) qualified to share results. Among PCPs declining to disclose, insufficient knowledge was the most common reason. In multivariable logistic regression, feeling qualified was the only variable significantly associated with agreeing to disclose results (OR 6.53, 95% CI 3.31, 12.88). In post-disclosure surveys (response rate=55%), PCPs reported largely positive experiences. Interview findings suggested that although PCPs valued the study-provided educational materials, they desired better integration of results and decision support into workflows.

CONCLUSION

Barriers exist to incorporating BRCA1/2 testing into primary care. Most PCPs declined to disclose their patients' BFOR results, although survey respondents were motivated and had positive disclosure experiences. PCP training and integrated decision support could be beneficial.

TRIAL REGISTRATION

ClinicalTrials.gov (NCT03351803), November 24, 2017.

Landscape of homologous recombination reversion mutations in gynecologic malignancies

5576

Background: Homologous recombination (HR) reversion mutations (REV) are biomarkers for predicting resistance to platinum and PARP inhibitor therapies. The biologic diversity of REV represents a diagnostic challenge. An automated computational approach was used to detect REV for analysis of genomic features of REV-positive ovarian epithelial, fallopian tube, and peritoneal cancers. Methods: Retrospective study of tissue (n = 23,612) and liquid biopsy (n = 869) samples from patients undergoing hybrid-capture comprehensive genomic profiling during routine clinical care 11/2012-03/2021. A proprietary algorithm tested for seven distinct REV mechanisms in BRCA1, BRCA2, PALB2, RAD51C, or RAD51D. For subjects with multiple samples, the earliest REV-positive sample was used for downstream analyses. Results: Among 23,866 ovarian epithelial, fallopian tube, and peritoneal cancers, 16.4% (n = 3,920) had at least one pathogenic variant (PV) in BRCA1 (10%, n = 2,383), BRCA2 (5.5%, n = 1,320), PALB2 (0.67%, n = 160), RAD51C (0.64%, n = 152), or RAD51D (0.47%, n = 113). 3.9% (154/3,920) of patients with one or more PV had REV. REV were found in tumors with PV in BRCA2 at twice the frequency of BRCA1 (6.0%, [79/1,320] vs 3.0% [71/2,383]; p < 0.001). REV involving RAD51D (1.8%, 2/113), RAD51C (0.7%, 1/152), or PALB2 (0.6%, 1/160) were rarer. A total of 193 REV pairs were identified. The most frequent REV mechanism was an exonic non-frameshift deletion completely encompassing a PV (45%, 87/193). Other recurrent mechanisms included restoration of the reading frame of a frameshift PV (21%, 42/193), replacement of a PV with a benign missense substitution at the same codon (16%, 32/193), and deletion with intronic breakpoints encompassing a PV (15%, 29/193). REV were significantly more prevalent in liquid biopsies than in tissue samples with PV (16% [20/124] vs. 3.5% [134/3,796]; p < 0.001). A range of 1-6 REV pairs were found per sample (liquid: 1-6, tissue: 1-3). Multiple REV per sample was more common in liquid biopsies (35% [7/20] vs. 11% [15/134]; p = 0.011). These differences likely reflect stage of disease and sampling of multiple subclones. Conclusions: BRCA2 PV are most frequently reverted in gynecologic tumors. REV are also common in tumors with BRCA1 PV and can more rarely occur in other HR genes. Liquid biopsy is enriched for detection of polyclonal resistance. Diverse REV mechanisms highlight a need for robust detection to incorporate REV in identifying treatment resistance and guiding downstream therapy selection.

A randomized phase Ib/II study of niraparib (nira) plus nivolumab (nivo) or ipilimumab (ipi) in patients (pts) with platinum-sensitive advanced pancreatic cancer (aPDAC)

4021

Background: Establishing alternatives to perpetual chemotherapy for pts with aPDAC has been proposed to address inevitable chemotherapy resistance and cumulative toxicity. Poly (ADP ribose) polymerase (PARP) inhibitors have shown clinical efficacy in this setting, and preclinical data suggest that the addition of immune checkpoint blockade (ICB) may offer synergistic tumor control. We performed a randomized, phase Ib/II study of nira plus anti-PD-1 (nivo) or nira plus anti-CTLA-4 (ipi) maintenance for pts with aPDAC who had not progressed after >4 mo of platinum-based therapy. Methods: After discontinuation of chemotherapy, pts were randomized 1:1 to nira 200mg PO daily plus either nivo 240mg IV q2 weeks (later amended to 480mg IV q4 weeks) or ipi 3mg/kg IV q3 weeks for four doses. Nira could be escalated to 300mg PO daily if tolerated. Pts were treated until progression or unacceptable toxicity. The primary endpoint was progression free survival at six months (PFS6) in each arm. Secondary endpoints included safety, OS, ORR, and outcomes by DNA damage repair (DDR) deficiencies. Pts were evaluable for safety if they had received > 1 dose of study treatment and for efficacy if they had also received > 1 follow-up imaging study. Based on historical data, the null hypothesis of PFS6 = 44% vs a 2-sided alternative hypothesis of PFS ≠ 44% was tested. 42 pts per arm provided 81% power for testing at a 5% significance level to detect inferior PFS6 < 27% or superior PFS6 > 61%. Results: As of Oct 2021, 91 pts were enrolled, of whom 84 were evaluable for efficacy (44 nira/nivo; 40 nira/ipi). The median potential follow-up was 23 mos. Most common treatment-related AEs were nira/nivo: thrombocytopenia (28%), arthralgia (25%), nausea (23%), and fatigue (23%) and nira/ipi: thrombocytopenia (45%), anemia (43%), fatigue (43%), nausea, (41%), AST increase (36%), rash (34%) and ALT increase (29%). 88% of AEs were grade 1-2. Efficacy results were: nira/nivo: PFS6 20.6% (95% CI 8.3-32.9, p = 0.0002), mPFS 1.9 mo and nira/ipi: PFS6 59.6% (95% CI 44.3-74.9, p = 0.045), mPFS 8.1 mo. Fifteen pts (8 nira/nivo; 7 nira/ipi) had pathogenic variants in BRCA or PALB2 . Excluding these: mPFS on nira/nivo was 1.9 mo (95% CI 1.8-1.9) and mPFS on nira/ipi was 7.6 mo (95% CI 4.0 – 11.1). Conclusions: In a randomized phase 1B/II study, nira/ipi as maintenance therapy met the primary endpoint of superior PFS6 while nira/nivo yielded inferior PFS6 for pts with aPDAC who had not progressed on first-line platinum-based chemotherapy. The benefit of nira/ipi maintenance persisted in pts without known DDR variants. Clinical trial information: NCT03404960. [Table: see text]

Landscape of homologous recombination reversion mutations in pancreaticobiliary malignancies

4156

Background: Homologous recombination (HR) pathway reversion mutations (REV) are emerging treatment resistance biomarkers for platinum and PARP inhibitor therapy. The wide diversity of REV presents a diagnostic challenge. We implemented an automated computational approach to detect REV and examined the genomic features of REV-positive pancreaticobiliary cancers. Methods: Retrospective study of tissue (n = 31,124) and liquid biopsy (n = 3,870) samples from patients undergoing hybrid-capture comprehensive genomic profiling during routine clinical care 11/2012-03/2021. A proprietary algorithm tested samples for seven distinct REV mechanisms in BRCA1, BRCA2, or PALB2. For subjects with multiple samples, the earliest REV-positive sample was used for downstream analyses. Results: 5.3% (1,866/34,994) of biliary and pancreatic primary tumors harbored one or more pathogenic variants (PV) in BRCA1 (1.4%, n = 499), BRCA2 (3.2%, n = 1,119), or PALB2 (0.81%, n = 282). Among patients with at least one PV in these genes, 2.4% (45/1,866) had REV. The majority of REV involved BRCA2 (82%, 37/45), significantly higher than the proportion of BRCA2 PV in the cohort overall (59%, 1,119/1,900; p = 0.022). The remainder of REV involved either BRCA1 (8.9%, 4/45) or PALB2 (8.9%, 4/45). A total of 63 REV pairs were identified. The most frequent REV mechanism was an exonic non-frameshift deletion completely encompassing a PV (36%, 23/63), followed by a frameshift restoring the reading frame of a pathogenic frameshift (23%, 15/63), a benign missense replacing a PV at the same codon (17%, 11/63), and deletion with intronic breakpoints causing loss of a PV (17%, 11/63). REV were approximately equally prevalent in liquid biopsy (2.8%, 5/178) and tissue samples (2.4% 40/1,688; p = 0.72). A range of 1-9 REV were found per sample (liquid biopsy = 1-9, tissue = 1-2), and liquid biopsy samples had a higher median REV per sample compared to tissue (2.0 vs. 1.0; p < 0.001), as well as a higher prevalence of multiple REV per sample (60% [3/5] vs 7.5% [3/40]; p = 0.013). These differences likely reflect stage of disease and sampling of multiple subclones. Conclusions: Although REV are uncommonly detected in pancreaticobiliary carcinomas, the presence of REV in BRCA2, BRCA1, and PALB2 in patients with pancreaticobiliary neoplasms supports HR as a therapeutic target in these cancers. Diverse REV mechanisms highlight a need for robust detection to incorporate REV in identifying treatment resistance and guiding therapy selection.

BRCA1/2 Mutations and Cardiovascular Function in Breast Cancer Survivors

Objective

Animal models suggest that BRCA1/2 mutations increase doxorubicin-induced cardiotoxicity risk but data in humans are limited. We aimed to determine whether germline BRCA1/2 mutations are associated with cardiac dysfunction in breast cancer survivors.

Methods

In a single-center cross-sectional study, stage I-III breast cancer survivors were enrolled according to three groups: (1) BRCA1/2 mutation carriers treated with doxorubicin; (2) BRCA1/2 mutation non-carriers treated with doxorubicin; and (3) BRCA1/2 mutation carriers treated with non-doxorubicin cancer therapy. In age-adjusted analysis, core-lab quantitated measures of echocardiography-derived cardiac function and cardiopulmonary exercise testing (CPET) were compared across the groups. A complementary in vitro study was performed to assess the impact of BRCA1 loss of function on human induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) survival following doxorubicin exposure.

Results

Sixty-seven women with mean (standard deviation) age of 50 (11) years were included. Age-adjusted left ventricular ejection fraction (LVEF) was lower in participants receiving doxorubicin regardless of BRCA1/2 mutation status (p = 0.03). In doxorubicin-treated BRCA1/2 mutation carriers and non-carriers, LVEF was lower by 5.4% (95% CI; −9.3, −1.5) and 4.8% (95% CI; −9.1, −0.5), respectively compared to carriers without doxorubicin exposure. No significant differences in VO_2max were observed across the three groups (p_overall = 0.07). Doxorubicin caused a dose-dependent reduction in viability of iPSC-CMs in vitro without differences between BRCA1 mutant and wild type controls (p > 0.05).

Conclusions

BRCA1/2 mutation status was not associated with differences in measures of cardiovascular function or fitness. Our findings do not support a role for increased cardiotoxicity risk with BRCA1/2 mutations in women with breast cancer.

Polygenic risk modeling for prediction of epithelial ovarian cancer risk

Polygenic risk scores (PRS) for epithelial ovarian cancer (EOC) have the potential to improve risk stratification. Joint estimation of Single Nucleotide Polymorphism (SNP) effects in models could improve predictive performance over standard approaches of PRS construction. Here, we implemented computationally efficient, penalized, logistic regression models (lasso, elastic net, stepwise) to individual level genotype data and a Bayesian framework with continuous shrinkage, "select and shrink for summary statistics" (S4), to summary level data for epithelial non-mucinous ovarian cancer risk prediction. We developed the models in a dataset consisting of 23,564 non-mucinous EOC cases and 40,138 controls participating in the Ovarian Cancer Association Consortium (OCAC) and validated the best models in three populations of different ancestries: prospective data from 198,101 women of European ancestries; 7,669 women of East Asian ancestries; 1,072 women of African ancestries, and in 18,915 BRCA1 and 12,337 BRCA2 pathogenic variant carriers of European ancestries. In the external validation data, the model with the strongest association for non-mucinous EOC risk derived from the OCAC model development data was the S4 model (27,240 SNPs) with odds ratios (OR) of 1.38 (95% CI: 1.28-1.48, AUC: 0.588) per unit standard deviation, in women of European ancestries; 1.14 (95% CI: 1.08-1.19, AUC: 0.538) in women of East Asian ancestries; 1.38 (95% CI: 1.21-1.58, AUC: 0.593) in women of African ancestries; hazard ratios of 1.36 (95% CI: 1.29-1.43, AUC: 0.592) in BRCA1 pathogenic variant carriers and 1.49 (95% CI: 1.35-1.64, AUC: 0.624) in BRCA2 pathogenic variant carriers. Incorporation of the S4 PRS in risk prediction models for ovarian cancer may have clinical utility in ovarian cancer prevention programs.

Abstract P2-11-21: Integration of an ancestrally unbiased polygenic risk score with the Tyrer-Cuzick breast cancer risk model

Background: Polygenic risk scores (PRS) have been shown to provide genomically informed breast cancer risk assessment in both carriers and non-carriers of predisposing genetic mutations. Risk stratification is further improved by combining a PRS with risk models incorporating traditional risk factors to generate a Combined Risk Score (CRS). We recently developed and validated a breast cancer PRS for women of diverse ancestries using ancestry-informative genetic markers. Here, we combine the diverse ancestry PRS with a clinical and family history-based model to develop an integrated genomically-informed and ancestrally unbiased risk assessment tool. Methods: The study sample included women in the U.S. without a personal history of breast cancer, referred for clinical genetic testing between June 2020 and March 2021, and who tested negative for pathogenic or likely pathogenic variants in breast cancer susceptibility genes. A CRS, incorporating a validated PRS and the TC model, was generated using a previously described Fixed-Stratified method that accounts for association between PRS and clinical risk factors. Association between the PRS and each clinical risk factor included in the Tyrer-Cuzick (TC) breast cancer risk model (version 7) was tested using linear regression with PRS as the dependent variable and the TC factor as an independent variable with adjustment for age and ancestry. We examined the rate of reclassification resulting from incorporation of PRS into the CRS by classifying women as having high (&gt;20%) remaining lifetime risk (RLR) versus low (≤20%) RLR according to both TC and CRS. Results: Among 68,803 women, 21,500 (31.2%) had one or more first degree relatives (FDR) with breast cancer. Approximately 10% of women reported only African ancestry and a similar percentage reported only Hispanic/Latina ethnicity (Table 1). Family history was significantly associated with PRS (p=1.0x10-76). After adjusting for multiple testing, no other factors showed significant association with PRS. Improved risk stratification of CRS over TC follows from two results: (1) We previously showed that PRS improved risk stratification above and beyond family history; (2) In the present study, PRS was not associated with any TC factor other than family history. Adding the PRS to the TC model significantly altered breast cancer risk estimates for women of all ancestries, with 17.3% of patients stratified differently by CRS versus TC alone. Differences in risk stratification (using the 20% threshold) for each self-reported ancestry are presented in Table 1. The CRS classified fewer patients (32.0%) as high RLR than the TC model alone (35.4%), with similar results for 5-year risk estimates. Conclusions: This is the first genomically-informed, integrated polygenic and traditional breast cancer risk model for US women referred for contemporary clinical genetic testing. This model advances the PRS component of a previously validated combined model. It effectively estimates 5-year and lifetime risk for breast cancer using a PRS with an objectively genetically determined ancestral composition, calibrated and validated for risk stratification in all ancestries. The model may reliably and responsibly inform risk reduction strategies such as enhanced surveillance and use of preventive medications.

Table 1.Self-Reported Ancestry/EthnicityNumber (%) of patientsHigh TC High CRS High TC and Low CRSLow TC and High CRSAll68,803 (100%)24,332 (35.4%)22,041 (32.0%)7,080 . (10.3%)4,789 . (7.0%)Asian1,450. (2.1%)487 (33.6%)475 (32.8%)94 . (6.5%)82 . (5.7%)African7,909 (11.5%)2,540 (32.1%)2,473 (31.3%)435 . (5.5%)368 . (4.7%)Hispanic6,481 . (9.4%)1,614 (24.9%)1,345 (20.9%)606 . (9.4%)346 . (5.3%)Non-European*19,225 (27.9%)5,701 (29.7%)5,297 (27.6%)1,429 . (7.4%)1,025 . (5.3%)European**46,640 (67.8%)17,507 (37.5%)15,733 (33.7%)5,328 . (11.4%)3,554 . (7.6%)*Includes any combination of Black/African, Middle Eastern, Pacific Islander, Asian, Hispanic/Latino and/or Native American ancestry. **Includes White/Non-Hispanic and/or Ashkenazi Jewish.

Citation Format: Elisha Hughes, Ryan Bernhisel, Holly Pederson, Braden Probst, Timothy Simmons, Susanne Wagner, Thaddeus Judkins, Eric Rosenthal, Benjamin Roa, Susan M. Domchek, Charis Eng, Judy Garber, Monique Gary, Ora K. Gordon, Jennifer Klemp, Semanti Mukherjee, Kenneth Offit, Funmi Olopade, Joseph Vijai, Jeffrey N. Weitzel, Pat Whitworth, Lamis Yehia, Allison Kurian, Mark Robson, Thomas P. Slavin, Alexander Gutin, Jerry S. Lanchbury. Integration of an ancestrally unbiased polygenic risk score with the Tyrer-Cuzick breast cancer risk model [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 P2-11-21.

Abstract P2-09-01: Population-based risk estimates of clinical subtypes of breast cancer among carriers of germline pathogenic variants in cancer predisposition genes

Introduction: The risk of specific clinical subtype of breast cancer (defined by ER and HER2 status) among women in the general population who are carriers of germline pathogenic variants (PVs) in cancer predisposition genes is not well-defined. Methods: A total of 13,153 women with breast cancer (ER+/HER2-: 9381; ER+/HER2+: 1462; ER-/HER2+: 690; and ER-/HER2-: 1620) and 25,005 unaffected women (controls) from nine studies within the CAnceR RIsk Estimates Related to Susceptibility (CARRIERS) consortium that were not enriched for family history or early onset disease were included in the present analysis. A multiplex amplicon-based panel was used to perform germline sequencing for cancer predisposition genes. Case-control associations for each of the four clinical subtype of breast cancer was performed for PVs in 5 common breast cancer predisposition genes (ATM, BRCA1, BRCA2, CHEK2 and PALB2) utilizing a logistic regression model adjusting for study, age at diagnosis, race/ethnicity and family history of breast cancer. Results: The frequency of PVs in 5 genes was 3.8% for ER+/HER2-, 6.2% for ER+/HER2+, 4.2% for ER-/HER2+ and 9.3% for ER-/HER2- subtypes. PVs in BRCA1 and BRCA2 were associated with high risk (Odds Ratio (OR) &gt;4) for all clinical subtypes of breast cancer, but the risk was highest (OR&gt;8) for ER-/HER2- breast cancer. PVs in PALB2 were associated with high risk (OR&gt;4) of ER-/HER2- and ER+/HER2+ subtypes and moderate risk (OR: 2-4) of ER+/HER2- breast cancer. Irrespective of the HER2 status, PVs in ATM were associated with a moderately increased risk (OR: 2-4) of ER+ breast cancer but the risk of ER- breast cancer was not elevated. In contrast, PVs in CHEK2 were associated with high risk (OR&gt;4) of ER+/HER2+ breast cancer and moderate risk (OR: 2-4) of ER+/HER2- and ER-/HER2+ breast cancer, but the risk of ER-/HER2- breast cancer was not elevated. Conclusions: This study provides population-based estimates of risk of specific clinical subtypes of breast cancer which will be useful for genetic counseling and targeting appropriate screening strategies in PV carriers based on subtype specific risks of breast cancer.

Citation Format: Siddhartha Yadav, Chunling Hu, Nicholas J. Boddicker, Eric Polley, Steven Hart, Rohan Gnanaolivu, Jie Na, Hongyan Huang, Song Yao, Celine M. Vachon, Lauren Teras, Jack A. Taylor, Dale P. Sandler, Julie R. Palmer, Janet E. Olson, Susan Neuhausen, Elena Martinez, Sara Lindstroem, Loic Le Marchand, Charles Kooperberg, Christopher Haiman, Mia M. Gaudet, James V. Lacey, Kimberly A. Bertrand, Leslie Bernstein, Paul W. Auer, Christine Ambrosone, Jeffrey N. Weitzel, Peter Kraft, David E. Goldgar, Katherine L. Nathanson, Susan M. Domchek, Fergus J. Couch, CARRIERS Consortium. Population-based risk estimates of clinical subtypes of breast cancer among carriers of germline pathogenic variants in cancer predisposition genes [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 P2-09-01.

PTEN Loss and BRCA1 Promoter Hypermethylation Negatively Predict for Immunogenicity in BRCA-Deficient Ovarian Cancer

PURPOSE

Ovarian cancers can exhibit a prominent immune infiltrate, but clinical trials have not demonstrated substantive response rates to immune checkpoint blockade monotherapy. We aimed to understand genomic features associated with immunogenicity in BRCA1/2 mutation-associated cancers.

MATERIALS AND METHODS

Using the Cancer Genome Atlas whole-exome sequencing, methylation, and expression data, we analyzed 66 ovarian cancers with either germline or somatic loss of BRCA1/2 and whole-exome sequencing, immunohistochemistry, and CyTOF in 20 ovarian cancers with germline BRCA1/2 pathogenic variants from Penn.

RESULTS

We found two groups of BRCA1/2 ovarian cancers differing in their immunogenicity: (1) 37 tumors significantly enriched for PTEN loss (11, 30%) and BRCA1 promoter-hypermethylated (10, 27%; P = .0016) and (2) PTEN wild-type (28 of 29 tumors) cancers, with the latter group having longer overall survival (OS; P = .0186, median OS not reached v median OS = 66.1 months). BRCA1/2-mutant PTEN loss and BRCA1 promoter-hypermethylated cancers were characterized by the decreased composition of lymphocytes estimated by gene expression (P = .0030), cytolytic index (P = .034), and cytokine expression but higher homologous recombination deficiency scores (P = .00013). Large-scale state transitions were the primary discriminating feature (P = .001); neither mutational burden nor neoantigen burden could explain differences in immunogenicity. In Penn tumors, PTEN loss and high homologous recombination deficiency cancers exhibited fewer CD3+ (P = .05), CD8+ (P = .012), and FOXP3+ (P = .0087) T cells; decreased PRF1 expression (P = .041); and lower immune costimulatory and inhibitory molecule expression.

CONCLUSION

Our study suggests that within ovarian cancers with genetic loss of BRCA1/2 are two subsets exhibiting differential immunogenicity, with lower levels associated with PTEN loss and BRCA hypermethylation. These genomic features of BRCA1/2-associated ovarian cancers may inform considerations around how to optimally deploy immune checkpoint inhibitors in the clinic.

Breast and Prostate Cancer Risks for Male BRCA1 and BRCA2 Pathogenic Variant Carriers Using Polygenic Risk Scores

BACKGROUND

Recent population-based female breast cancer and prostate cancer polygenic risk scores (PRS) have been developed. We assessed the associations of these PRS with breast and prostate cancer risks for male BRCA1 and BRCA2 pathogenic variant carriers.

METHODS

483 BRCA1 and 1318 BRCA2 European ancestry male carriers were available from the Consortium of Investigators of Modifiers of BRCA1/2 (CIMBA). A 147-single nucleotide polymorphism (SNP) prostate cancer PRS (PRSPC) and a 313-SNP breast cancer PRS were evaluated. There were 3 versions of the breast cancer PRS, optimized to predict overall (PRSBC), estrogen receptor (ER)-negative (PRSER-), or ER-positive (PRSER+) breast cancer risk.

RESULTS

PRSER+ yielded the strongest association with breast cancer risk. The odds ratios (ORs) per PRSER+ standard deviation estimates were 1.40 (95% confidence interval [CI] =1.07 to 1.83) for BRCA1 and 1.33 (95% CI = 1.16 to 1.52) for BRCA2 carriers. PRSPC was associated with prostate cancer risk for BRCA1 (OR = 1.73, 95% CI = 1.28 to 2.33) and BRCA2 (OR = 1.60, 95% CI = 1.34 to 1.91) carriers. The estimated breast cancer odds ratios were larger after adjusting for female relative breast cancer family history. By age 85 years, for BRCA2 carriers, the breast cancer risk varied from 7.7% to 18.4% and prostate cancer risk from 34.1% to 87.6% between the 5th and 95th percentiles of the PRS distributions.

CONCLUSIONS

Population-based prostate and female breast cancer PRS are associated with a wide range of absolute breast and prostate cancer risks for male BRCA1 and BRCA2 carriers. These findings warrant further investigation aimed at providing personalized cancer risks for male carriers and informing clinical management.

Risks of breast and ovarian cancer for women harboring pathogenic missense variants in BRCA1 and BRCA2 compared with those harboring protein truncating variants

PURPOSE

Germline genetic testing for BRCA1 and BRCA2 variants has been a part of clinical practice for >2 decades. However, no studies have compared the cancer risks associated with missense pathogenic variants (PVs) with those associated with protein truncating (PTC) variants.

METHODS

We collected 582 informative pedigrees segregating 1 of 28 missense PVs in BRCA1 and 153 pedigrees segregating 1 of 12 missense PVs in BRCA2. We analyzed 324 pedigrees with PTC variants in BRCA1 and 214 pedigrees with PTC variants in BRCA2. Cancer risks were estimated using modified segregation analysis.

RESULTS

Estimated breast cancer risks were markedly lower for women aged >50 years carrying BRCA1 missense PVs than for the women carrying BRCA1 PTC variants (hazard ratio [HR] = 3.9 [2.4-6.2] for PVs vs 12.8 [5.7-28.7] for PTC variants; P = .01), particularly for missense PVs in the BRCA1 C-terminal domain (HR = 2.8 [1.4-5.6]; P = .005). In case of BRCA2, for women aged >50 years, the HR was 3.9 (2.0-7.2) for those heterozygous for missense PVs compared with 7.0 (3.3-14.7) for those harboring PTC variants. BRCA1 p.[Cys64Arg] and BRCA2 p.[Trp2626Cys] were associated with particularly low risks of breast cancer compared with other PVs.

CONCLUSION

These results have important implications for the counseling of at-risk women who harbor missense PVs in the BRCA1/2 genes.

Germline Pathogenic Variants in Cancer Predisposition Genes Among Women With Invasive Lobular Carcinoma of the Breast

PURPOSE

To determine the contribution of germline pathogenic variants (PVs) in hereditary cancer testing panel genes to invasive lobular carcinoma (ILC) of the breast.

MATERIALS AND METHODS

The study included 2,999 women with ILC from a population-based cohort and 3,796 women with ILC undergoing clinical multigene panel testing (clinical cohort). Frequencies of germline PVs in breast cancer predisposition genes (ATM, BARD1, BRCA1, BRCA2, BRIP1, CDH1, CHEK2, PALB2, PTEN, RAD51C, RAD51D, and TP53) were compared between women with ILC and unaffected female controls and between women with ILC and infiltrating ductal carcinoma (IDC).

RESULTS

The frequency of PVs in breast cancer predisposition genes among women with ILC was 6.5% in the clinical cohort and 5.2% in the population-based cohort. In case-control analysis, CDH1 and BRCA2 PVs were associated with high risks of ILC (odds ratio [OR] > 4) and CHEK2, ATM, and PALB2 PVs were associated with moderate (OR = 2-4) risks. BRCA1 PVs and CHEK2 p.Ile157Thr were not associated with clinically relevant risks (OR < 2) of ILC. Compared with IDC, CDH1 PVs were > 10-fold enriched, whereas PVs in BRCA1 were substantially reduced in ILC.

CONCLUSION

The study establishes that PVs in ATM, BRCA2, CDH1, CHEK2, and PALB2 are associated with an increased risk of ILC, whereas BRCA1 PVs are not. The similar overall PV frequencies for ILC and IDC suggest that cancer histology should not influence the decision to proceed with genetic testing. Similar to IDC, multigene panel testing may be appropriate for women with ILC, but CDH1 should be specifically discussed because of low prevalence and gastric cancer risk.

A randomized study of genetic education versus usual care in tumor profiling for advanced cancer in the ECOG-ACRIN Cancer Research Group (EAQ152)

Background

Enthusiasm for precision oncology may obscure the psychosocial and ethical considerations associated with the implementation of tumor genetic sequencing.

Methods

Patients with advanced cancer undergoing tumor‐only genetic sequencing in the National Cancer Institute Molecular Analysis for Therapy Choice (MATCH) trial were randomized to a web‐based genetic education intervention or usual care. The primary outcomes were knowledge, anxiety, depression, and cancer‐specific distress collected at baseline (T0), posteducation (T1) and after results (T2). Two‐sided, 2‐sample t tests and univariate and multivariable generalized linear models were used.

Results

Five hundred ninety‐four patients (80% from NCI Community Oncology Research Program sites) were randomized to the web intervention (n = 293) or usual care (n = 301) before the receipt of results. Patients in the intervention arm had greater increases in knowledge (P for T1‐T0 < .0001; P for T2‐T0 = .003), but there were no significant differences in distress outcomes. In unadjusted moderator analyses, there was a decrease in cancer‐specific distress among women (T0‐T1) in the intervention arm but not among men. Patients with lower health literacy in the intervention arm had greater increases in cancer‐specific distress and less decline in general anxiety (T0‐T1) and greater increases in depression (T0‐T2) in comparison with those receiving usual care.

Conclusions

Web‐based genetic education before tumor‐only sequencing results increases patient understanding and reduces distress in women. Refinements to the intervention could benefit low‐literacy groups and men.

In the Communication and Education in Tumor Profiling (COMET) study, patients with advanced cancer undergoing tumor genetic sequencing in the National Cancer Institute Molecular Analysis for Therapy Choice (MATCH) trial have been randomized to a web‐based genetic education intervention or usual care. Web‐based genetic education has resulted in increased patient understanding and reduced distress in female patients with cancer.

Targeted BRCA1/2 population screening among Ashkenazi Jewish individuals using a web-enabled medical model: An observational cohort study

PURPOSE

This study aimed to evaluate uptake and follow-up using internet-assisted population genetic testing (GT) for BRCA1/2 Ashkenazi Jewish founder pathogenic variants (AJPVs).

METHODS

Across 4 cities in the United States, from December 2017 to March 2020, individuals aged ≥25 years with ≥1 Ashkenazi Jewish grandparent were offered enrollment. Participants consented and enrolled online with chatbot and video education, underwent BRCA1/2 AJPV GT, and chose to receive results from their primary care provider (PCP) or study staff. Surveys were conducted at baseline, at 12 weeks, and annually for 5 years.

RESULTS

A total of 5193 participants enrolled and 4109 (79.1%) were tested (median age = 54, female = 77.1%). Upon enrollment, 35.1% of participants selected a PCP to disclose results, and 40.5% of PCPs agreed. Of those tested, 138 (3.4%) were AJPV heterozygotes of whom 21 (15.2%) had no significant family history of cancer, whereas 86 (62.3%) had a known familial pathogenic variant. At 12 weeks, 85.5% of participants with AJPVs planned increased cancer screening; only 3.7% with negative results and a significant family history reported further testing.

CONCLUSION

Although continued follow-up is needed, internet-enabled outreach can expand access to targeted GT using a medical model. Observed challenges for population genetic screening efforts include recruitment barriers, improving PCP engagement, and increasing uptake of additional testing when indicated.

Risk of Late-Onset Breast Cancer in Genetically Predisposed Women

PURPOSE

The prevalence of germline pathogenic variants (PVs) in established breast cancer predisposition genes in women in the general population over age 65 years is not well-defined. However, testing guidelines suggest that women diagnosed with breast cancer over age 65 years might have < 2.5% likelihood of a PV in a high-penetrance gene. This study aimed to establish the frequency of PVs and remaining risks of breast cancer for each gene in women over age 65 years.

METHODS

A total of 26,707 women over age 65 years from population-based studies (51.5% with breast cancer and 48.5% unaffected) were tested for PVs in germline predisposition gene. Frequencies of PVs and associations between PVs in each gene and breast cancer were assessed, and remaining lifetime breast cancer risks were estimated for non-Hispanic White women with PVs.

RESULTS

The frequency of PVs in predisposition genes was 3.18% for women with breast cancer and 1.48% for unaffected women over age 65 years. PVs in BRCA1, BRCA2, and PALB2 were found in 3.42% of women diagnosed with estrogen receptor (ER)-negative, 1.0% with ER-positive, and 3.01% with triple-negative breast cancer. Frequencies of PVs were lower among women with no first-degree relatives with breast cancer. PVs in CHEK2, PALB2, BRCA2, and BRCA1 were associated with increased risks (odds ratio = 2.9-4.0) of breast cancer. Remaining lifetime risks of breast cancer were ≥ 15% for those with PVs in BRCA1, BRCA2, and PALB2.

CONCLUSION

This study suggests that all women diagnosed with triple-negative breast cancer or ER-negative breast cancer should receive genetic testing and that women over age 65 years with BRCA1 and BRCA2 PVs and perhaps with PALB2 and CHEK2 PVs should be considered for magnetic resonance imaging screening.

Association of Inherited Mutations in DNA Repair Genes with Localized Prostate Cancer

Background:

Identification of germline mutations in DNA repair genes has significant implications for the personalized treatment of individuals with prostate cancer (PrCa).

Objective:

To determine DNA repair genes associated with localized PrCa in a diverse academic biobank and to determine genetic testing burden.

Design, setting, and participants:

A cross-sectional study of 2391 localized PrCa patients was carried out.

Outcome measurements and statistical analysis:

Genetic ancestry and mutation rates (excluding somatic interference) in 17 DNA repair genes were determined in 1588 localized PrCa patients and 3273 cancer-free males. Burden testing within individuals of genetically determined European (EUR) and African (AFR) ancestry was performed between biobank PrCa cases and cancer-free biobank and gnomAD males.

Results and limitations:

AFR individuals with localized PrCa had lower DNA repair gene mutation rates than EUR individuals (1.4% vs 4.0%, p = 0.02). Mutation rates in localized PrCa patients were similar to those in biobank and gnomAD controls (EUR: 4.0% vs 2.8%, p = 0.15, vs 3.1%, p = 0.04; AFR: 1.4% vs 1.8%, p = 0.8, vs 2.1%, p = 0.5). Gene-based rare variant association testing revealed that only BRCA2 mutations were significantly enriched compared with gnomAD controls of EUR ancestry (1.0% vs 0.28%, p = 0.03). Of the participants, 21% and 11% met high-risk and very-high-risk criteria; of them, 3.7% and 6.2% had any germline genetic mutation and 1.0% and 2.5% had a BRCA2 mutation, respectively. Limitations of this study include an analysis of a relatively small, single-institution cohort.

Conclusions:

DNA repair gene germline mutation rates are low in an academic biobank cohort of localized PrCa patients, particularly among individuals of AFR genetic ancestry. Mutation rates in genes with published evidence of association with PrCa exceed 2.5% only in high-risk, very-high-risk localized, and node-positive PrCa patients. These findings highlight the importance of risk stratification in localized PrCa patients to identify appropriate patients for germline genetic testing.

Patient summary:

In the majority of patients who develop localized prostate cancer, germline genetic testing is unlikely to reveal an inherited DNA repair mutation, regardless of race. High-risk features increase the possibility of a germline DNA repair mutation.

Analysis of mutation status and homologous recombination deficiency in tumors of patients with germline BRCA1 or BRCA2 mutations and metastatic breast cancer: OlympiAD

BACKGROUND

Presence of a germline BRCA1 and/or BRCA2 mutation (gBRCAm) may sensitize tumors to poly(ADP-ribose) polymerase (PARP) inhibition via inactivation of the second allele, resulting in gene-specific loss of heterozygosity (gsLOH) and homologous recombination deficiency (HRD). Here we explore whether tissue sample testing provides an additional route to germline testing to inform treatment selection for PARP inhibition.

PATIENTS AND METHODS

In this prespecified exploratory analysis, BRCA1 and/or BRCA2 mutations in blood samples (gBRCAm) and tumor tissue (tBRCAm) were analyzed from patients with human epidermal growth factor receptor 2 (HER2)-negative metastatic breast cancer and known gBRCAm, enrolled in the phase III OlympiAD trial. The frequency and nature of tBRCAm, HRD score status [HRD-positive (score ≥42) versus HRD-negative (score <42) using the Myriad myChoice® CDx test] and rates of gsLOH were determined, and their impact on clinical efficacy (objective response rate and progression-free survival) was explored.

RESULTS

Tissue samples from 161/302 patients yielded tBRCAm, HRD and gsLOH data for 143 (47%), 129 (43%) and 125 (41%) patients, respectively. Concordance between gBRCAm and tBRCAm was 99%. gsLOH was observed in 118/125 (94%) patients [BRCA1m, 73/76 (96%); BRCA2m, 45/49 (92%)]. A second mutation event was recorded for two of the three BRCA1m patients without gsLOH. The incidence of HRD-negative was 16% (21/129) and was more common for BRCA2m (versus BRCA1m) and/or for hormone receptor-positive (versus triple-negative) disease. Olaparib antitumor activity was observed irrespective of HRD score.

CONCLUSIONS

gBRCAm identified in patients with HER2-negative metastatic breast cancer by germline testing in blood was also identified by tumor tissue testing. gsLOH was common, indicating a high rate of biallelic inactivation in metastatic breast cancer. Olaparib activity was seen regardless of gsLOH status or HRD score. Thus, additional tumor testing to inform PARP inhibitor treatment selection may not be supported for these patients.

Relationship of established risk factors with breast cancer subtypes

Background

Breast cancer is a heterogeneous disease, divided into subtypes based on the expression of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2). Subtypes have different biology and prognosis, with accumulating evidence of different risk factors. The purpose of this study was to compare breast cancer risk factors across tumor subtypes in a large, diverse mammography population.

Methods

Women aged 40–84 without a history of breast cancer with a screening mammogram at three United States health systems from 2006 to 2015 were included. Risk factor questionnaires were completed at mammogram visit, supplemented by electronic health records. Invasive tumor subtype was defined by immunohistochemistry as ER/PR+HER2−, ER/PR+HER2+, ER, and PR−HER2+, or triple‐negative breast cancer (TNBC). Cox proportional hazards models were run for each subtype. Associations of race, reproductive history, prior breast problems, family history, breast density, and body mass index (BMI) were assessed. The association of tumor subtypes with screen detection and interval cancer was assessed using logistic regression among invasive cases.

Results

The study population included 198,278 women with a median of 6.5 years of follow‐up (IQR 4.2–9.0 years). There were 4002 invasive cancers, including 3077 (77%) ER/PR+HER2−, 300 (8%) TNBC, 342 (9%) ER/PR+HER2+, and 126 (3%) ER/PR−HER2+ subtype. In multivariate models, Black women had 2.7 times higher risk of TNBC than white women (HR = 2.67, 95% CI 1.99–3.58). Breast density was associated with increased risk of all subtypes. BMI was more strongly associated with ER/PR+HER2− and HER2+ subtypes among postmenopausal women than premenopausal women. Breast density was more strongly associated with ER/PR+HER2− and TNBC among premenopausal than postmenopausal women. TNBC was more likely to be interval cancer than other subtypes.

Conclusions

These results have implications for risk assessment and understanding of the etiology of breast cancer subtypes. More research is needed to determine what factors explain the higher risk of TNBC for Black women.

The predictive ability of the 313 variant-based polygenic risk score for contralateral breast cancer risk prediction in women of European ancestry with a heterozygous BRCA1 or BRCA2 pathogenic variant

PURPOSE

To evaluate the association between a previously published 313 variant-based breast cancer (BC) polygenic risk score (PRS313) and contralateral breast cancer (CBC) risk, in BRCA1 and BRCA2 pathogenic variant heterozygotes.

METHODS

We included women of European ancestry with a prevalent first primary invasive BC (BRCA1 = 6,591 with 1,402 prevalent CBC cases; BRCA2 = 4,208 with 647 prevalent CBC cases) from the Consortium of Investigators of Modifiers of BRCA1/2 (CIMBA), a large international retrospective series. Cox regression analysis was performed to assess the association between overall and ER-specific PRS313 and CBC risk.

RESULTS

For BRCA1 heterozygotes the estrogen receptor (ER)-negative PRS313 showed the largest association with CBC risk, hazard ratio (HR) per SD = 1.12, 95% confidence interval (CI) (1.06-1.18), C-index = 0.53; for BRCA2 heterozygotes, this was the ER-positive PRS313, HR = 1.15, 95% CI (1.07-1.25), C-index = 0.57. Adjusting for family history, age at diagnosis, treatment, or pathological characteristics for the first BC did not change association effect sizes. For women developing first BC < age 40 years, the cumulative PRS313 5th and 95th percentile 10-year CBC risks were 22% and 32% for BRCA1 and 13% and 23% for BRCA2 heterozygotes, respectively.

CONCLUSION

The PRS313 can be used to refine individual CBC risks for BRCA1/2 heterozygotes of European ancestry, however the PRS313 needs to be considered in the context of a multifactorial risk model to evaluate whether it might influence clinical decision-making.

Risk of Breast Cancer Among Carriers of Pathogenic Variants in Breast Cancer Predisposition Genes Varies by Polygenic Risk Score

PURPOSE

This study assessed the joint association of pathogenic variants (PVs) in breast cancer (BC) predisposition genes and polygenic risk scores (PRS) with BC in the general population.

METHODS

A total of 26,798 non-Hispanic white BC cases and 26,127 controls from predominately population-based studies in the Cancer Risk Estimates Related to Susceptibility consortium were evaluated for PVs in BRCA1, BRCA2, ATM, CHEK2, PALB2, BARD1, BRIP1, CDH1, and NF1. PRS based on 105 common variants were created using effect estimates from BC genome-wide association studies; the performance of an overall BC PRS and estrogen receptor-specific PRS were evaluated. The odds of BC based on the PVs and PRS were estimated using penalized logistic regression. The results were combined with age-specific incidence rates to estimate 5-year and lifetime absolute risks of BC across percentiles of PRS by PV status and first-degree family history of BC.

RESULTS

The estimated lifetime risks of BC among general-population noncarriers, based on 10th and 90th percentiles of PRS, were 9.1%-23.9% and 6.7%-18.2% for women with or without first-degree relatives with BC, respectively. Taking PRS into account, more than 95% of BRCA1, BRCA2, and PALB2 carriers had > 20% lifetime risks of BC, whereas, respectively, 52.5% and 69.7% of ATM and CHEK2 carriers without first-degree relatives with BC, and 78.8% and 89.9% of those with a first-degree relative with BC had > 20% risk.

CONCLUSION

PRS facilitates personalization of BC risk among carriers of PVs in predisposition genes. Incorporating PRS into BC risk estimation may help identify > 30% of CHEK2 and nearly half of ATM carriers below the 20% lifetime risk threshold, suggesting the addition of PRS may prevent overscreening and enable more personalized risk management approaches.