Application of genetic testing criteria for hereditary breast cancer in South Africa.

Purpose: Breast cancer (BC) is the commonest cancer in South African women. A proportion are associated with a pathogenic or likely pathogenic (P/LP) variant in a BC susceptibility gene. Clinical guidelines for genetic testing are used to optimise variant detection while containing costs. We assessed the detection rate in women of diverse ancestries who met the South African National Department of Health (NDOH) testing guidelines, and analysed relationships between testing criteria, participant characteristics and presence of a BRCA1/2 P/LP variant.

Methods: Records from 376 women with BC who met NDOH criteria and had genetic testing were included. Demographic, clinical and test result data were collated to describe detection rates according to criteria met, and a multivariate analysis conducted to find variables most frequently associated with a P/LP variant.

Results: P/LP variant prevalence in women meeting NDOH testing criteria was 19.9% (75/376). Women meeting ≥ 2 guideline criteria were over twice as likely to have a P/LP variant (OR 2.27, 95%CI 1.27-4.07, p = 0.006), highlighting the guidelines' capacity to stratify risk. Family history (OR 1.97; 95%CI 1.05-3.70, p = 0.03) and Black African ancestry (OR 2.58; 95%CI 1.28-5.18, p < 0.01) were independently associated with having a BRCA1/2 P/LP variant when controlling for other variables. Notably, although Black African participants were less likely to report a family history, those that did had higher odds of a P/LP variant in BRCA1/2.

Conclusion: These results demonstrate the usefulness of the NDOH guidelines in women of diverse ancestries and provide insight into the factors associated with P/LP variants in understudied African populations.