Determinants of triple-negative breast cancer among African patients: Early results from The African Cancer Atlas.

1133 Background: Triple-negative breast cancer (TNBC) is disproportionately common among women of African ancestry and is associated with aggressive clinical behavior and limited therapeutic options. Understanding demographic and contextual determinants of TNBC across African countries is essential to improving prevention, early detection, and precision oncology strategies. Using harmonized data from The African Cancer Atlas (TACA)--an initiative of Yemaachi Biotech, we examined factors associated with TNBC across Côte d’Ivoire, Ghana, Kenya, Nigeria, and Seychelles. Methods: We analyzed 236 participants with complete immunohistochemistry data enrolled in TACA. Associations between TNBC and demographic variables were assessed using Wilcoxon rank-sum tests, Fisher’s exact tests, and multivariable logistic regression. Results: TNBC accounted for 38.1% of breast cancers in the cohort. TNBC had prevalence rates ranging from 21.1% in Kenya to 68.1% in Nigeria (p<0.001). Seychelles exhibited no TNBC cases (0/23). TNBC prevalence among females was 38.5% (89/231), compared with 20.0% (1/5) among the few male participants. Women in Nigeria had markedly higher odds of TNBC compared with Kenya (OR 10.4, 95% CI 3.72–31.4, p<0.001). Women in Ghana also demonstrated increased odds (OR 2.55, 95% CI 1.10–6.12, p=0.032). Age showed no significant association with TNBC (mean age 51.6 years for TNBC vs. 50.2 years for non-TNBC, p=0.6), though the 60–69 age group showed a modestly increased proportion of TNBC (38.1%, OR 0.26, 95% CI 0.07–0.93, p=0.042, relative to 50–59). Education level was significantly associated with TNBC (p=0.004). Women with no formal education had a 59.2% TNBC prevalence (29/49), compared with 26.9% among those with primary education (18/67, OR 0.69, 95% CI 0.26–1.85) and 33.3% among those with higher education (17/51, OR 0.77, 95% CI 0.28–2.14). Family history of cancer was also associated with TNBC (p=0.006). Among women reporting a positive family history, 23.8% had TNBC (15/63), compared with 76.2% with non-TNBC (48/63). Conclusions: TNBC prevalence in this multi-country African cohort was high and characterized by substantial geographic variation, with Nigeria demonstrating the highest burden. Lower educational attainment and family history of cancer were also associated with TNBC, independent of country. These findings highlight the importance of considering sociodemographic and contextual factors when designing TNBC-focused screening and treatment strategies and underscore the need for country-specific precision oncology approaches in African settings.