Breast Cancer Survival and Survival Gap Apportionment in Sub-Saharan Africa: African Breast Cancer – Disparities in Outcomes ABC-DO Cohort

Abstract

Background: Breast cancer is the second leading cause of cancer death in women in sub-Saharan Africa, yet there are few large-scale survival studies with rich clinical and epidemiologic data and few losses to follow-up to inform intervention strategies needed to avert premature deaths. Methods: In the hospital-based African Breast Cancer – Disparities in Outcomes (ABC-DO) cohort, characterized by rich sociodemographic, clinical and treatment data, 2214 women newly diagnosed with breast cancer across five Sub-Saharan African countries were prospectively followed using a trimonthly mobile phone contact protocol. Flexible proportional mortality models were used to estimate observed survival, hazard ratios and predict survival under scenarios of modifying risk factors. Findings: Among 2156 women followed up to three years, 879 (41%) died, 1118 (52%) were alive and 159 (7%) were censored early. Three-year survival was 50% overall, but varied between races in Namibia (90% white, 69% mixed-race and 56% in black women) and South Africa (76% mixed-race, 59% black) and between countries: 44 to 47% in Uganda and Zambia and 36% in Nigeria. Ten percent of all women died within 6 months of diagnosis, but three-year survival remained low (58%) conditional on surviving to this time-point. Among survival determinants, improvements in early diagnosis and treatment were predicted to result in the largest survival gains of up to a combined 22% absolute increase, compared to the contributions of social inequalities (up to 5%), non-receptor positive tumours (up to 4%) and young age or HIV (<2% each). Interpretation: Large variations in breast cancer survival in sub-Saharan African countries demonstrate that improvements are possible. At least one-third of the projected 416000 breast cancer deaths that will occur in this region in the next decade could be prevented through achievable down-staging and treatment improvements. Improving survival in socially disadvantaged women warrants special attention. Funding Statement: Susan G Komen Foundation and International Agency for Research on Cancer Declaration of Interests: The authors confirm no competing interests. Ethics Approval Statement: ABC-DO was approved by all institutional ethics committees and each woman provided informed consent.