Abstract PO5-08-11: Genetic Landscape of Early Breast Cancer in an Ashkenazi Jewish Cohort

Abstract Background: The Ashkenazi Jewish (AJ) population exhibits a distinctive mutation profile in BRCA1 and BRCA2 (BRCA1/2), characterized by 3 common founder mutations: BRCA1 185delAG, BRCA1 5382insC, and BRCA2 6174delT. These 3 mutations are associated with 10% of invasive breast cancer (BC) cases among AJ women. However, the frequency of non-founder pathogenic variants in BRCA1/2 and other BC-related genes in AJ women with BC remains unclear. Methods: This retrospective study included AJ patients diagnosed with stage I-II human epidermal receptor growth factor 2 negative BC between 2004-2022 at the Weill Cornell Breast Center. We collected clinicopathological characteristics and genetic information to determine the frequency of predisposing mutations in BC and non-BC related genes in AJ patients with early BC. We also analyzed the clinicopathological characteristics and outcomes of patients with and without germline mutations in these genes. Results: The study included 232 self-identified AJ patients, with 98% being females. The median age at BC diagnosis was 62 years (IQR: 50-70). Stage I and II cancers accounted for 68% and 32% of cases, respectively. Hormone receptor positivity (HR+) was observed in 71% of patients, while 29% had triple-negative tumors. Genetic testing was performed on 88% (n=203) of the patients, while 5% of patients declined to undergo genetic testing. Among the tested patients, 12% (n=25/203) had pathogenic variants in BRCA1 or BRCA2, with 44% and 16% of these corresponding to the BRCA1 and BRCA2 founder mutations, respectively. Testing beyond BRCA1/2 genes was conducted on 154 patients, and only 6% (n=9/154) were found to have pathogenic variants in CHEK2, while no mutations were detected in other prevalent BC-related genes, including PALB2 and ATM. Fourteen-percent of patients had pathogenic mutations in other genes including APC, CFTR, FH, DIS3L2, FANCC, MUTYH, NF1 and VHL. The frequency of pathogenic BRCA1/2 variants was inversely proportional to the age at BC diagnosis: 50% (n=8/16), 21% (n=8/39), 15% (n=6/40), and 3% (n=3/108) of patients diagnosed at age < 40, 40-49, 50-59, and >60 years, respectively, had a pathogenic variant in either BRCA1 or BRCA2. The frequency of founder mutations varied according to age at diagnosis: 63%, 75%, 17%, and 100% for patients aged < 40, 40-49, 50-59, and >60 years, respectively. Patients with BRCA1/2 mutations exhibited higher-risk clinicopathological features compared to those without mutations, including a higher proportion of high histological grade (88%), and triple-negative tumors (76%). Mastectomy was the primary surgical treatment for 56% and 23% of patients with and without BRCA1/2 mutations, respectively. No difference in disease-free survival was found between patients with and without BRCA1/2 mutations with a median follow up of 3 years (IQR: 1-4). Conclusions: In our cohort, 17% of AJ patients with early BC carried a pathogenic variant in a BC-related gene, with BRCA1/2 being the most commonly affected genes. The proportion of pathogenic variants in BRCA1/2 showed an inverse correlation with the age at BC diagnosis, reaching up to 50% in patients diagnosed under the age of 40. These findings contrast with the lower prevalence of pathogenic variants in BRCA1/2 (38%) reported in the existing literature for this age group. Additionally, 8% of patients had pathogenic variants in other tested cancer genes carrying a genetic predisposition to colorectal cancer (CRC). These findings contribute to our understanding of the genetic landscape of early BC in the AJ population and emphasize the importance of comprehensive genetic testing, particularly among young patients. These results also suggest the need for earlier and more frequent CRC screening in a population of BC patients that may not be adhering to recommended guidelines. Furthermore, our study provides insight into how this genetic landscape may vary when analyzing late-stage BC in women of AJ heritage. Citation Format: Laura Munoz Arcos, Eleonora Nicolò, Maira Pires, Letizia Pontolillo, Leticia Varella, Tessa Cigler, Eleni Andreopolu, Anne Moore, Ashley Schreier, Carlos Munoz-Zuluaga, Lisa Newman, Georgia Syrnioti, Massimo Cristofanilli. Genetic Landscape of Early Breast Cancer in an Ashkenazi Jewish Cohort [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-08-11.