Survival deficits in young women with breast cancer in sub-Saharan Africa: the African Breast Cancer-Disparities in Outcomes cohort.

Abstract

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. 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. 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). 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.