15 years of experience of an oncogenetics service in the northeast of Brazil.

Abstract

e22522 Background: The Oncogenetics service at the Federal University of Bahia was implemented in 2007 and since then has been offering pre- and post-test genetic counseling for cancer susceptibility genes, mainly tumors associated with King's syndrome in the population of the state of Bahia. This is a mixed population of about 80% of African ancestry. Methods: Between the years 2007 to 2021, 462 probands and their families have already been evaluated by NGS analysis, Sanger sequencing. Large rearrangements were detected by multiplex ligation-dependent probe amplification (MLPA) for the BRCA1 and BRCA2 genes. Results: The mean age at diagnosis was 41 years. Pathogenic/probably pathogenic mutations were founded in 118 patients: 67 had breast cancer, 09 with ovarian cancer, 26 with more than one tumor, 15 without cancer, and 01 with another tumor type. Most of the pathogenic variants were located in the BRCA1 gene (27 variants), the two most frequent variants being: c.211G > A (13 probands) and c.3331_3334delCAAG (18 probands), both of Iberian origin. Of patients with mutation, 9.8% had large rearrangements in BRCA1 and 11.5% in BRCA2. Bilateral breast cancer appears predominantly in patients with BRCA1 (4) and BRCA2 (1) variants. In this study, only two mutations in BRCA described as of African origin were found in two patients. Other pathogenic mutations appear in ATM, BARD1, BRIP1, CDH1, CHEK2, FAM175A, FANCM, MSH6, NBN, NF2, PALB2, RAD51, SDHB, SLX4, and TP53 genes. Variants of uncertain significance were identified in 71 patients. Conclusions: The population of the state of Bahia has a peculiar mutational profile, containing mutations that are not very frequent in other regions of the country. Despite being a population with high African ancestry, most mutations are of European origin.