BROCA gene panel testing in African descendants from northeastern Brazil: Genetic susceptibility profile of an admixed population

1572 Background: The rising global burden of breast cancer (BC) in developing countries demands innovative interventions to accelerate progress in cancer control and prevention. Given the high rates of aggressive young onset breast cancer in Brazil, we sought to examine genetic susceptibility to the disease in the State of Bahia in the Northeast of Brazil, which has the largest population of African descendants. Methods: We screened cases, high-risk breast cancer patients with and without family history of breast cancer, and controls (cancer-free women) for twenty-eight breast cancer susceptibility genes using a validated targeted capture and multiplex sequencing approach – the BROCA panel. Each participant gave informed consent under IRB approved protocols and provided clinical-pathological and epidemiological data. Results: A total of 292 consecutive and unrelated individuals (173 cases and 119 controls) were included. Nearly 2/3rds of the cases (116/173) and about 90% of the controls (108/119) self-reported as African-descendant. Mutations considered pathogenic were identified in 37 (21.4%) cases and in one control (0.84%, RAD51C c.266insA), OR = 27.75 and p = 0.008. The mutated genes in cases were BRCA1 (in 12 patients), BRCA2 (10), ATM (3), PALB2 (3), BRIP1 (3), BRCA2/ BARD1 (1), FAM175A (1), FANCM (1), NBN (1), SLX4 (1) and TP53 (1). Three recurrent mutations accounted for 12.4% (9/37) of the total: 3 BRCA1 c.3331_3334delCAAG (known European mutation), 3 BRCA1 c.211A > G (known Galician mutation), and 3 PALB2c.1671_1674delTATT (novel mutation). Conclusions: Mutations in BRCA1 and BRCA2 (64.85%) or another breast cancer gene (35.15%) occur in one in five high-risk breast cancer patients in the largest study of Northeastern Brazil to date, and a significant proportion were recurrent mutations of European origin, which can be explained by the admixture pattern of the Brazilian population. This result underscores the importance of using multigene panel in cancer genetic epidemiologic research of understudied populations where unexpected findings, such as the recurrent and novel variant in PALB2 c.1671_1674delTATT, can be detected.