Citations

1514 Background: The prevalence of germline mutations in non-white patients with breast cancer and the germline genetic drivers of breast cancer risk in non-white populations are largely unknown. Methods: The study population included 77,900 women with breast cancer (Non-Hispanic white: 57,003; Black: 6,722; Asian: 4,183; Hispanic: 5,194; Ashkenazi-Jewish: 4,798) who underwent germline multigene panel testing of cancer predisposition genes from March 2012 to December 2016. The prevalence of predisposition gene mutations in racial and ethnic populations relative to non-Hispanic Whites was assessed while accounting for age at diagnosis of breast cancer, family history of breast and ovarian cancer, and estrogen receptor status of breast tumors. Associations between mutations in each gene and breast cancer risk were evaluated using reference controls. Results: The overall frequency of pathogenic mutations in known breast cancer predisposition genes was 9.1% for non-Hispanic Whites, 9.8% for African Americans, 10.2% for Hispanics, 7.6% for Ashkenazi-Jewish, and 7.5% for Asians. BRCA1 mutations were enriched (p < 0.05) and CHEK2 mutations were under-represented in all racial and ethnic populations relative to non-Hispanic Whites. BRCA2 and BARD1 mutations were enriched in African Americans and Hispanics relative to non-Hispanic Whites, whereas PALB2 and RAD51C mutations were enriched in Hispanics. Among genes with mutation counts large enough for assessment, mutations in BARD1, BRCA1, BRCA2, PALB2 and TP53 were significantly associated with clinically relevant increased risks (odds ratio (OR) > 2) of breast cancer across all ethnicities and races. Rates of variants of uncertain significance were highest among Asians (29%), followed by blacks (27%), Hispanics (21%), non-Hispanic whites (16%) and Ashkenazi-Jews (14%). Conclusions: While there is some similarity across ethnic groups, substantial heterogeneity exists in the prevalence of mutations in breast cancer predisposition genes across major racial and ethnic groups in the US population. These findings contribute to our understanding of breast cancer risk and have significant implications for genetic testing, screening, and management of patients with an inherited predisposition to breast cancer, with a need for continued analysis with increased cohort size in ethnic minority groups.

1501 Background: Despite BC risk reduction of 50-65% by preventive endocrine therapy (ET), very few at-risk women choose to take them. A woman’s perceived BC risk correlates with uptake of ET. A PRS comprised of 77 BC genetic susceptibility loci (Single Nucleotide Polymorphisms (SNP) improves the accuracy of risk prediction for BC. We examined the impact of the addition of individualized PRS BC risk prediction to standard risk calculator estimates on intent to take BC prevention medication. Methods: Eligible women had ≥5% 10 yr BC Tyrer-Cuzick risk (IBIS) or 5 year Gail score ≥3%, with no history of BC or hereditary BC syndrome. Standard BC risk estimates (IBIS or Gail) were incorporated into the counselling on BC preventive ET. A self-reported questionnaire at baseline quantified intention to take ET and explored factors associated with this decision. Blood samples were obtained and genotyped for 77 SNPs, individualized PRS were calculated then incorporated into IBIS and Gail predictions for 5 yr, 10 yr, & lifetime BC risk. At a second visit, PRS risk & prevention recommendations were revisited. Post visit questionnaires assessed change in intent to take ET. Multivariable linear regression was performed to assess impact of baseline variables on change in intent to take medication. Results: From 2016 to 2017, 151 women in Canada & USA were enrolled, median age: 56.1 (range 36-76.4), 35.6% were premenopausal, 98.7% were Caucasian. Median 5yr, 10yr, & lifetime IBIS risk estimates were 3.8% (2.0-11.5), 7.9% (5.0-23.1), and 25.3% (5.5 to 92.2). PRS increased BC risk estimates in 84 (55.6%) and reduced BC risk estimates in 67 (44%) women. After PRS risk counselling, intention to take ET significantly changed (p<0.001): 41.9% of those with increased PRS were more inclined, and 46.7% of women with decreased PRS were less inclined to take ET. On multivariable regression, increase in PRS (p<0.0001) and less concern about ET side effects (p<0.0001) were associated with greater intent to take ET. Conclusions: In high risk women, PRS significantly changed BC risk estimates & intent to take preventive ET. Further assessments of the impact of PRS scores on compliance with ET are warranted. Clinical trial information: NCT02517593.

1048 Background: Germline BRCA1/2 ( gBRCA) mutations (mt) are some of the few actionable alterations in mBC patients. The PARP inhibitors olaparib/talazoparib are more effective than chemotherapy (ctx) in patients with a gBRCAmt and HER2 negative(-) mBC. In mBC patients the TNT-study suggested a better progression-free survival (PFS) for g BRCA-mt compared to patients with a gBRCA1/2 wildtype (wt) when treated with platinum and not with a taxane. Otherwise little is known about the prognostic effect of g BRCA1/2mt in mBC patients. Methods: PRAEGNANT (NCT02338167) is a prospective mBC registry with a focus on molecular biomarkers. Patients were eligible for this analysis if their mBC was HER2- and treated with ctx for the first time (referred to as first-line ctx). Hormone receptor (HR) positive patients had to have all hormone therapies exhausted. Mutation frequencies and their association with patient and tumor characteristics were analyzed. Multivariable Cox regression models were built with commonly established prognostic factors and g BRCA mutation status as predictors of PFS and overall survival (OS) from first-line ctx. Results: Out of 2932 PRAEGNANT patients, 576 were HER2- and received first-line ctx. Of those 529 patients with g BRCA genotype results and follow up information could be analyzed. 24 patients (4.5%) had a g BRCAmt (11 BRCA1, 13 BRCA2). Mutation rate in HR positive patients was 3.9% (17/432) and 7.2% (7/97) in HR negative patients. Most patients received ctx either as the first treatment in the metastatic setting or after one line of hormone therapy (n=382; 72.2%). Multivariable Cox regression models showed an adjusted hazard ratio for gBRCAmt vs. gBRCAwt patients of 0.70 (95% CI: 0.43-1.15) for PFS and of 0.41 (95% CI: 0.18-0.93) for OS. Most frequent ctx treatments were taxane (52%) or capecitabine based (21%). Additionally, the prevalence of somatic BRCA1/2 mutations in this population will be presented. Conclusions: In this HER2- mBC population under ctx g BRCA mutation rates were within the expected range of about 5%. Within the analyzed population patients with a g BRCA mutation seemed to have a better OS than patients without a mutation. PFS results pointed in the same direction without statistical significance. However, with only 24 mutations replication of these results in additional cohorts is warranted. Clinical trial information: NCT02338167.

104 Background: The identification of pathogenic mutations in breast cancer susceptibility genes through clinical genetic testing leads to focused screening and prevention strategies for women at increased risk of cancer. However, the frequency of mutations and the risks of cancer associated with breast cancer predisposition genes has not been established for the African American population. Methods: Germline DNA samples from African American women (5,054 breast cancer cases and 4,993 age-matched unaffected controls) from 10 U.S. studies were tested for mutations in 20 established breast cancer predisposition genes using a QIAseq multiplex amplicon panel as part of the “CAnceR RIsk Estimates Related to Susceptibility” (CARRIERS) study. The frequency of mutations in each gene and associations between mutations and breast cancer risk, adjusted for study design, age, and first-degree family history of breast cancer, were evaluated. Results: The mean age at diagnosis of breast cancer cases was 54.4 years and the mean age of controls was 55.2 years. 18.2% of cases and 10.8% of controls reported a first-degree family history of breast cancer. Pathogenic mutations in any of the 20 breast cancer predisposition genes were identified in 7.6% of breast cancer cases and 2.4% of controls. In multivariable analyses, mutations in BRCA1, BRCA2, and PALB2 were associated with high risks of breast cancer (odds ratio (OR) > 5.0). Mutations in CHEK2 were associated with moderate risks of breast cancer (OR > 2.0), whereas mutations in ATM had lower clinical relevance (OR = 1.8). Mutations in BRCA1, BRCA2, PALB2, and RAD51D, but not CHEK2 or ATM, were associated with increased risks of estrogen receptor negative breast cancer. Conclusions: Cancer predisposition genes confer similar risks of breast cancer in the African American population as in non-Hispanic Whites. These studies provide important insights into the risks of breast cancer associated with predisposition gene mutations in the African American population.

The field of germline genetic testing for breast cancer (BC) risk has evolved substantially in the last decade. The introduction of multigene panel testing (MGPT) led to an urgent need to understand the cancer risk associated with several genes included in the panels. Although the research on understanding the cancer risk associated with mutations in several genes continues, there is also a need to understand the modifying effects of race and ethnicity, family history, and BC pathology on the prevalence of germline mutations and associated BC risk. Furthermore, polygenic risk scores (PRSs) to predict BC risk in patients with or without germline mutations in cancer-predisposition genes are now available for clinical use, although data on the clinical utility of PRSs are lacking. In patients with advanced BC associated with BRCA1/2 mutation, olaparib and talazoparib are now approved for treatment. In addition, molecular profiling studies are being used to clarify the BC tumor biology in mutation carriers to identify potential therapeutic options. In this article, we discuss these advances in the field of germline genetic testing and highlight current limitations and implications for clinical care.

Abstract Background: Male breast cancer (MBC) is rare, and usually managed by extrapolation from female breast cancer. We report on the characteristics and survival outcomes of MBC patients from Mayo Clinic Rochester (MCR). Methods: Medical records of MBC patients treated at MCR during a 25-year period (1990-2015) were reviewed. Demographic variables, tumor characteristics, recurrences, and overall survival (OS) were collected. Progression free survival (PFS) and OS were estimated by the Kaplan-Meier method. Multivariate Cox-proportional hazard regression was used to identify predictors of OS. Results: One hundred sixty-seven patients were included in the final analysis, with a median follow-up of 58 months after diagnosis. Baseline characteristics are presented in Table 1. Eighty percent of patients with ER-positive tumors received endocrine therapy. Among men with stage I-III disease, approximately 90% underwent mastectomy, and 44% received adjuvant chemotherapy. The 5-year locoregional and distant recurrence rates for patients with stage I-III disease were 4.4% and 21.5%, respectively. The 5-year PFS and OS for patients with stage I-III disease were 65.5% and 80.1%, respectively. In a multivariate analysis assessing predictors of OS in patients with stage I-III disease, older age (HR 1.05; 95% CI: 1.02 – 1.09), stage II (HR 11.06; 95% CI: 3.84 – 31.85) or stage III disease (HR 14.74; 95% CI (3.99 – 54.45), and omission of surgery (HR 45.33; 95% CI: 3.97 – 517.32) were associated with poorer OS, while endocrine therapy (HR 0.21, 95% CI: 0.09 – 0.51) was associated with better OS. ER, PR, HER2 and grade were not independently prognostic. The median OS for stage IV patients was 10 months, though this 11-man cohort was too small to allow assessment of prognostic factors in advanced male breast cancer. Conclusions: MBC remains an understudied condition. Prognostic factors in this stage I-III disease are consistent with those identified in other MBC retrospective cohorts. Prospective studies are needed to better understand the unique clinical features of MBC, and to improve outcomes, particularly for advanced disease. Table 1:Baseline characteristics N=167 Median age at diagnosis (Years)64.4 Ethnicity/Race: Caucasian131 (78.4%)African American4 (2.4%)Other or unknown32 (19.2%) Overall AJCC 7th edition stage: Stage I39 (23.4%)Stage II80 (47.9%)Stage III32 (19.2%)Stage IV11 (6.6%)Unknown5 (3.0%) Grade: 18 (4.8%)247 (28.1%)3101 (60.5%)Unknown12 (7.1%) ER status: Negative8 (4.8%)Positive153 (91.6%)Unknown6 (3.6%) PR status: Negative17 (10.2%)Positive141 (84.4%)Unknown9 (5.4%) HER-2 status: Negative70 (41.9%)Positive12 (7.2%)Unknown85 (50.9%) Citation Format: Yadav S, Leon-Ferre RA, Jimenez RE, Hawse JR, Hieken TJ, Couch FJ, Boughey JC, Ruddy KJ. Clinical characteristics and survival of patients with male breast cancer: The Mayo Clinic experience [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-19-05.

Abstract Background: The LAR subtype is a genomically distinct subset of TNBC. Using a large cohort of non-metastatic TNBC patients (pts) with long term follow-up, we sought to further characterize the clinicopathologic features and outcomes of LAR vs non-LAR TNBC. Methods: From a cohort of 9982 women with surgically-treated non-metastatic breast cancer, 605 met criteria for TNBC (ER/PR&lt;1% and HER2-negative) by central pathology. RNA extracted from 304 FFPE tumor specimens using the HighPure RNA extraction kit was subjected to TruSeq RNA Access library preparation and sequencing on a HiSeq2500. Adequate RNA was available for 283 pts. Tumors were classified as LAR or non-LAR using a shrunken centroid model, CABAL (Clustering Among BAsal and Luminal androgen receptor). In addition to previously described analyses [Leon-Ferre et al, Breast Cancer Res Treat 2017], immunohistochemical (IHC) androgen receptor (AR) staining was performed and the impact of various parameters on invasive disease-free survival (IDFS) and overall survival (OS) was assessed using Cox proportional hazards models. Results: 58 (20%) tumors were classified as LAR and 225 (80%) as non-LAR. Compared to non-LAR, LAR pts were older (mean age 65 vs 54) and more often postmenopausal (79%vs53%), both p=0.01. Apocrine histology was more common among LAR tumors (21%vs0%), which were also lower grade (grade3: 69%vs95%) and had lower Ki-67 (Ki-67&gt;15%: 64%vs82%), all p&lt;0.01. Additionally, LAR tumors had lower median stromal tumor infiltrating lymphocytes (TILs, 20%vs25%) and were less frequently lymphocyte-predominant [≥50% stromal or intratumoral TILs (19%vs32%)], although neither reached statistical significance. AR IHC was available for 223 of 283 tumors. Median AR IHC score in LAR was 65% (range 0-100%) vs 0% (range 0-90%) in non-LAR. T/N stage, surgery type, and receipt of adjuvant chemotherapy (AdjCT) or radiotherapy were similar between LAR and non-LAR. LAR pts had shorter IDFS and OS compared to non-LAR (5.6 vs 11.8 yrs and 10.8 vs 20.8 yrs, respectively), although this did not reach statistical significance. Test of proportional hazard assumption was not significant for IDFS or OS (p = 0.30 and 0.09). IDFS estimates were numerically higher in LAR vs non-LAR (80.2%vs70.5%,p = 0.92) at 3yrs post-diagnosis; whereas the opposite was true (40.9%vs55.6%,p = 0.07) after 10yrs. OS estimates at 3 and 5yrs were similar between LAR and non-LAR, but at 10yrs OS was inferior in LAR (40.9%vs66.4%,p = 0.24). In a univariate analysis including both LAR and non-LAR, older age, higher N stage, lower TILs and absence of AdjCT were associated with poorer IDFS and OS. In a multivariate analysis, higher N stage and absence of AdjCT remained associated with both poorer IDFS and OS; while lower stromal TILs were associated with poorer IDFS (p=0.01), and with a trend towards poorer OS (p=0.07). Conclusions: LAR TNBCs occurred in older women, were lower grade, and had lower TIL density than nonLAR tumors. While significant differences in IDFS or OS were not demonstrated, LAR pts exhibited a numerically lower risk of a disease event at 3yrs, but higher risk by 10yrs compared to nonLAR pts. In the entire cohort, higher N stage, absence of AdjCT and lower TILs were independently associated with poorer outcomes. Citation Format: Leon-Ferre RA, Polley M-Y, Liu H, Kalari KR, Boughey JC, Liu MC, Cafourek V, Negron V, Ingle JN, Thompson KJ, Tang X, Barman P, Carlson E, Visscher DW, Carter JC, Couch FJ, Goetz MP. Characteristics, outcomes and prognostic factors of luminal androgen receptor (LAR) triple-negative breast cancer (TNBC) [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P3-08-01.

Abstract Background: Chemotherapy can damage the ovaries and cause amenorrhea, a surrogate for infertility. Young women often wish to understand and minimize their risk of chemotherapy-related amenorrhea (CRA). However, the incidence of CRA with regimens that do not include either an anthracycline or cyclophosphamide is poorly studied. For patients with HER-2 positive disease, these anthracycline and cyclophosphamide-sparing regimens (e.g., docetaxel-carboplatin) are common (in combination with Her-2 directed therapy) in both the neoadjuvant and adjuvant settings. Methods: Women diagnosed with breast cancer under age 50 and within the past 10 years were recruited through a Dr. Susan Love Research Foundation Army of Women e-mail blast. Those who provided their contact information were mailed a consent form and medical record authorization form. Participants then received a web-based survey that inquired about receipt of and type of chemotherapy (including date of last dose) and date of last menstrual period (LMP). Patient-reported LMP was compared to date of final chemotherapy dose to determine if the LMP occurred before (defined as “CRA”) or after the last chemotherapy dose. When available, medical record data was used in place of survey data regarding type of chemotherapy used. Exclusion criteria included: LMP prior to diagnosis date, receipt of multiple chemotherapy regimens or no chemotherapy regimens, receipt of ovarian suppression medications (which interfere with interpretation of menstrual data), surgical menopause prior to or at the same time as diagnosis, a cancer diagnosis more than 10 years prior, incomplete menstrual data on the survey, report of an unknown chemotherapy regimen, and no date available for the last chemotherapy dose without an LMP within a month prior to survey completion. Fisher Exact test was used to compare CRA rates between regimens. Rates after two anthracycline-sparing regimens (taxane/cyclophosphamide; taxane/carboplatin) were compared to rates after anthracycline/cyclophosphamide/taxane. Results: 273 women consented to participate in this study, 258 of whom filled out the web survey. 151 of them were eligible for this analysis with a median age at diagnosis of 41 (range 24-49) and a median time from last chemotherapy dose to survey of 62.5 months (range 2-138). CRA occurred in 51.2% of the 86 participants who received an anthracycline, cyclophosphamide, and a taxane, in 41.9% of the 43 participants who received only a taxane and cyclophosphamide (p=0.35), and in 13.3% of the 15 participants who received carboplatin with a taxane (p=0.01). When the 11 patients who were &lt;12 months since last chemotherapy were excluded, CRA rates changed minimally. Age did not differ by regimen, but median time since chemotherapy was shorter in the taxane/carboplatin group (35 months vs. 68 months). Trastuzumab with or without pertuzumab was administered in 100% of patients who received carboplatin/taxane, in 23.3% of patients who received taxane and cyclophosphamide, and in 22.1% of patients who received anthracycline/cyclophosphamide/taxane. Conclusions: This study suggests that carboplatin/taxane may be substantially less gonadotoxic than cyclophosphamide-based (neo)adjuvant regimens. Further research is necessary to confirm these findings. Citation Format: Gast KC, Cathcart-Rake EJ, Norman A, Eshragi L, Obidegwu N, Yost K, Nichols HB, Rosenberg S, Su HI, Stewart E, Couch F, Vachon C, Ruddy KJ. Regimen-specific rates of chemotherapy-related amenorrhea in breast cancer survivors [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P1-12-10.