Survival deficits in young women with breast cancer in Sub-Saharan africa: the ABC-DO cohort

Background Women diagnosed with breast cancer (BC) at young (<40 years) ages generally have lower survival than their older counterparts. With its young population structure, sub-Saharan Africa (SSA) provides an informative setting to examine survival among young BC patients, including consideration of their extended reproductive lives and HIV comorbidities. Methods We established a prospective cohort of women aged ≥18 years newly diagnosed with incident BC in five SSA countries during 2014-2017, followed actively for up to 7 years. Overall survival, net survival and Cox model hazard ratios (HRs) were used to assess the association between age at diagnosis and all-cause mortality. Results Among 2093 women, 459 (21.9%) were diagnosed <40 years (young women). 5-year net survival was 36% (95% CI 31-40) in young women, which was 8-14 percentage points lower than that for those diagnosed in their 40 s, 50 s, 60 s and 70 s+, being 43%, 45%, 47% and 50%, respectively. Compared to women diagnosed at 40-59 years, young women had 1.17-fold (95% CI: 1.02-1.35) higher mortality rates, unexplained by triple negative BC and HIV, both less prevalent in young women than at 40-59 years. Adjustment for socio-demographic, clinical and treatment factors hardly altered results, except for adjustment for a pregnancy within 3 years: HR 1.09 (95% CI, 0.93-1.28). Conclusion Early onset BC in SSA was associated with lower survival compared to women aged 40-59. This excess mortality was restricted to BCs diagnosed within 3 years postpartum, thus identifying a patient group with specific early detection, treatment support and research needs.