Breast cancer risk in women from Ghana carrying rare germline pathogenic mutations

Abstract

Background: Risk estimates for women carrying germline mutations in breast cancer susceptibility genes are mainly based on studies of European ancestry women. Methods: We investigated associations between pathogenic variants (PV) in 34 genes with breast cancer risk in 871 cases (307 estrogen receptor (ER)-positive, 321 ER-negative, and 243 ER-unknown) and 1,563 controls in the Ghana Breast Health Study (GBHS), and estimated lifetime risk for carriers. We compared results to those for European, Asian and African-American ancestry women. Results: The frequency of PV in GBHS for nine breast cancer genes was 8.38% in cases and 1.22% in controls. Relative risk estimates for overall breast cancer were: OR (95% CI)=13.70 (4.03-46.51) for BRCA1, 7.02 (3.17-15.54) for BRCA2, 17.25 (2.15-138.13) for PALB2, 5/0 cases/controls for TP53, and 2.10, (0.72-6.14) for moderate-risk genes combined (ATM, BARD1, CHEK2, RAD51C, RAD52D). These estimates were similar to those previously reported in other populations and were modified by ER status. No other genes evaluated had mutations associated at P<0.05 with overall risk. The estimated lifetime risks for mutation carriers in BRCA1, BRCA2 and PALB2 and moderate risk genes were 18.4%, 9.8%, 22.4% and 3.1%, respectively, markedly lower than in Western populations with higher baseline risks. Conclusions: We confirmed associations between PV and breast cancer risk in Ghanaian women and provide absolute risk estimates that could inform counseling in Ghana and other West African countries. Impact: These findings have direct relevance for genetic counseling in West Africa since currently available data is primarily from Western populations