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.

backgroundThere are few estimates of breast cancer survival and its determinants at 5 years and beyond in sub-Saharan Africa. We aimed to estimate survival up to 7 years, estimate annual mortality risk, and apportion survival gaps.

methodsThe African Breast Cancer-Disparities in Outcomes (ABC-DO) prospective cohort study was done at eight hospitals across five sub-Saharan African countries (Namibia, Nigeria, South Africa, Uganda, and Zambia). We prospectively recruited women (aged ≥18 years) who attended hospital with suspected breast cancer. Vital status was updated telephonically once every 3 months for 7 years. We collected detailed sociodemographic, clinical, and treatment data. The primary outcome was overall survival. We estimated age-standardised net survival, conditional survival, and predicted survival gains if there were favourable shifts in the distribution of prognostic factors aligned with the WHO Global Breast Cancer Initiative (GBCI).

findingsBetween Sept 8, 2014, and Dec 31, 2017, 2313 women were recruited and followed up to Jan 1, 2022, and for a further year in South Africa. We excluded 87 women without breast cancer, 14 women from small racial groups (eight White and six Asian women in South Africa), 57 women with previous treatment or possible recurrences, and two women without follow-up data. The remaining 2153 (93%) women were categorised by country and race, as follows: three groups in Namibia (60 White women, 50 mixed race women, and 367 Black women), two in South Africa (37 mixed race women and 638 Black women), and one group of Black women in each of Uganda (419 women), Zambia (198 women), and Nigeria (384 women). During follow-up to at most 7 years, 1323 (61%) of 2153 women died, 672 (31%) were alive at administrative censoring, and 158 (7%) were lost to follow-up, giving crude survival at 3 years, 5 years, and 7 years of 51%, 40%, and 33%, respectively. Large between-country variations in 5-year age-standardised net survival were observed: 35-42% in Zambia and Nigeria; 52-58% in Black women in Uganda, South Africa, and Namibia; and over 83% in non-Black Namibian women. The annual probability of death (1-year conditional net survival, censored before the COVID-19 pandemic) declined generally from 2-3 years after diagnosis, but remained at 8-21% for Black women in Namibia, Uganda, and Nigeria during the fifth year after diagnosis. Reaching the GBCI 60% stage I or II target and accessing treatment would lead to an approximate reduction in deaths by a third among Black women in Namibia, Nigeria, South Africa, Uganda, and Zambia.

interpretationSurvival after breast cancer is poor in several sub-Saharan African countries, with a substantial risk of death even among women who have survived beyond 3 years after diagnosis. Understanding and preventing deaths among longer-term breast cancer survivors requires further research.

fundingNational Cancer Institute, Susan G Komen, and International Agency for Research on Cancer. TRANSLATIONS: For the Yoruba, Hausa, Igbo, Luganda and French translations of the abstract see Supplementary Materials section.