P2-13-07: Prevalence of Germline BRCA1 and BRCA2 Deleterious Mutations in Brazilian Patients with High-Risk of Breast and Ovarian Cancer

Background: Germline mutations in the BRCA1/2 genes account for the majority of hereditary breast ovarian cancer (HBOC). Distribution and prevalence of clinically relevant mutations in BRCA1/2 differ among different populations. All of the Brazilian studies published to date have not performed complete sequencing of both genes, restricting their analyses to selected exons. In addition, a highly heterogeneous mutation spectrum was observed. The lack of data concerning the prevalence and profile of BRCA1/2 deleterious mutation and the appropriated screening criteria for DNA sequencing in the Brazilian population complicates the design of screening strategies.

Objective: To accurately determine the contribution of BRCA1/2 germline mutations in a well characterized sample of Brazilian breast and ovarian high-risk pts.

Methodology: A total of 73 unrelated pts attending a Brazilian public hospital from September 2005 to July 2006, with HBOC risk ≥10% according to Frank, Evans or BRCAPRO algorithms, underwent complete sequencing and MLPA analysis of BRCA1/2 genes. Demographic data and tumor pathological features were extracted from prospectively registered medical records.

Results: Mean age, median of cancer cases in families and median score by Frank, Evans and BRCAPRO algorithms were respectively 48y (24-78), 4 (0-13), 11.2 (0-56,3), 13.4 (0,1-100) and 16 (2-75). A total of 79 unknown clinical significance mutations were identified: 44 in BRCA1 and 35 in BRCA2. Known deleterious mutations were identified in 8 pts. Four in BRCA1: R71G at exon 5, 5382insC at exon 20 (2 patients) and R1751X at exon 20; and four in BRCA2: R2318X at exon 13, R3128X at exon 25, 5844del5 and 6633del5 at exon 11. Several polymorphisms were found in all pts. No mutation was detected by MLPA technique. One novel frameshift deleterious mutation in BRCA2: 6610insTT at exon 11 which results in a stop codon was detected in a breast cancer patient and in four of her relatives from a family with high-risk of HBOC. Taking into account the novel mutation, the prevalence of BRCA1/2 mutation in high-risk pts in our cohort is 12,3%. Pts characteristics presented in [table 1]. Conclusion: To the best of our knowledge, the study represents the first report of the complete sequencing and MLPA analysis of BRCA1/2 genes in large Brazilian series of HBOC high-risk pts. The prevalence of germline mutations found in the present study was similar to the reported by other studies examining high-risk populations.