Abstract 51: Breast Cancer Overall Survival, Annual Risks of Death, and Survival Gap Apportionment in Sub-Saharan Africa (ABC-DO): 7-Year Follow-Up of a Prospective Cohort Study

Abstract Purpose: To provide estimates of breast cancer survival and investigate its determinants at five years and beyond in Sub-Saharan Africa (SSA). Methods: The prospective African Breast Cancer-Disparities in Outcomes (ABC-DO) cohort study recruited women ≥18 years with a new clinical or histological diagnosis of breast cancer at eight major hospitals in Namibia, South Africa, Uganda, Zambia, and Nigeria. Vital status was updated telephonically trimonthly for seven years. We estimated age-standardized net survival (ASNS), conditional survival and predicted survival gains if there were favourable shifts in the distribution of prognostic factors aligned with WHO’s Global Breast Cancer Initiative (GBCI). Results: Between September 8, 2014, and December 31, 2017, 2313 women were recruited and followed to January 1, 2022, and for a further year in South Africa, 2153 of whom were eligible. Of these, 1323 (61·4%) died, 672 (31·1%) remained alive, and 158 (7·3%) were lost to follow-up, giving overall survival at 3, 5 and 7 years of 51%, 40% and 33% respectively. Large between-country variations in 5-year ASNS were observed: 35–42% in Zambia and Nigeria, 52–58% in Black women in Uganda, South Africa and Namibia, and over 84% in mixed race and White Namibian women. The annual probability of death (1- NS, censored prior to Covid) declined generally from 2 to 3 years post-diagnosis, but remained at 8–21% for Black women in Namibia, Uganda and Nigeria during the fifth year post-diagnosis. Reaching the GBCI 60% stage I/II target, and accessing treatment would lead to an approximate one-third reduction in deaths amongst Black women. Conclusion: At present, survival in breast cancer patients is low in several SSA countries, with the risk of dying remaining substantial even amongst women who have survived over 3 years. Understanding and preventing deaths among longer-term survivors needs addressing. Citation Format: Tingting Mo, Maureen Joffe, Moses Galukande, Groesbeck Parham, Annelle Zietsman, Isabel dos- Santos-Silva, Valerie McCormack. Breast Cancer Overall Survival, Annual Risks of Death, and Survival Gap Apportionment in Sub-Saharan Africa (ABC-DO): 7-Year Follow-Up of a Prospective Cohort Study [abstract]. In: Proceedings of the 13th Annual Symposium on Global Cancer Research; 2025 Sep 16. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2025;34(12_Suppl):Abstract nr 51.