Genetic Susceptibility to Breast Cancer in Sub-Saharan African Populations

Breast cancer (BC) is the most common cancer among African women and is the second most common cause of cancer deaths in Africa as estimated by GLOBOCAN 2018.1 Cancer incidence is increasing in Africa1 and is associated largely with lifestyle changes, resulting from increased urbanization.2 Ferlay et al3 predicted a 49% increase in BC incidence across Africa between 2018 and 2040, an increase faster than any other region in the world. The International Association of Cancer Registries cancer incidence report includes data for only 20 of 46 sub-Saharan African (SSA) countries,4 and it is likely that the incidence of BC is under-reported owing to lack of infrastructure for cancer diagnosis in resource-constrained countries in SSA.5 Also, owing to the large burden of communicable and other noncommunicable diseases in SSA, most resources are directed at controlling these diseases.6,7 Cancer research, especially molecular research, in SSA is often deprioritized against other pressing public health concerns.8 CONTEXT Key Objective Both rare and common genetic variants contribute to the risk of breast cancer (BC). Much is known about the genetics of BC in populations of European origin. Our objective was to review studies of genetic susceptibility to BC in the populations of sub-Saharan Africa to identify knowledge gaps and propose study designs to address these. Knowledge Generated A total of 22 studies were identified in 10 of 46 countries in sub-Saharan Africa. Rare variants predicted to be pathogenic were detected most commonly in the BRCA1, BRCA2, and PALB2 genes. There were few studies of common genetic variants, none of which provided strong evidence for association with BC risk. Relevance Knowledge of genetic factors contributing to BC risk has important implications for patients and their families both for genetic counseling and for potential access to new therapies, which improve survival and reduce side effects.