Abstract
BACKGROUND: Women diagnosed with breast cancer at young ages (younger than 40 years) generally have lower survival than their older counterparts. With its young population structure, sub-Saharan Africa provides an informative setting to examine survival among young patients with breast cancer, including consideration of the extended reproductive lives and HIV comorbidities. METHODS: We established a prospective cohort of women aged 18 years and older newly diagnosed with breast cancer in five sub-Saharan African countries during 2014-2017, who were actively followed 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 under age 40 years ("young" women). Five-year net survival was 36% (95% confidence interval [CI] = 31% to 40%) in these young women, which was 8-14 percentage points lower than that for those diagnosed in their 40s, 50s, 60s, and 70s or older, being 43%, 45%, 47%, and 50%, respectively. Compared with women diagnosed at age 40-59 years, young women had 1.17-fold (95% CI = 1.02 to 1.35) higher mortality rates, unexplained by triple-negative breast cancer and HIV which were both less prevalent in young women than in those aged 40-59 years. Adjustment for sociodemographic, clinical, and treatment factors hardly altered results, except for adjustment for having had a pregnancy within the past 3 years (HR = 1.09, 95% CI = 0.93 to 1.28). CONCLUSION: Early onset breast cancer in sub-Saharan Africa was associated with lower survival compared with women aged 40-59 years. This excess mortality was restricted to young women whose breast cancer was diagnosed within 3 years postpartum, thus identifying a patient group with specific early detection, treatment support and research needs.