Breast Cancer Survival in Sub-Saharan Africa—Diversity Across Disparities

Abstract

Even as breast cancer incidence and mortality have steadily increased throughout the low-and middle-income world, full descriptions of typical patient outcomes have been lacking. 1 Limenih et al 2 should be commended for preparing a comprehensive and carefully designed systematic review and meta-analysis summarizing overall survival patterns among patients with breast cancer living in sub-Saharan Africa (SSA), the world's poorest region. Synthesizing data from 49 studies, they estimate that the regionwide survival for patients newly diagnosed with breast cancer at 1 year is 79%; at 3 years, 56%; and at 5 years, 40%. They also demonstrate a pattern of improving survival over time and with increasing development. Estimated 5-year survival reached 46% to 47% in studies conducted after 2014 compared with just 24% to 26% in those conducted earlier. Five-year survival also steadily increased as countries moved up the ladder on the United Nations Development Programme's human development index (HDI), with estimates of 36% for countries with low HDI, 46% for those with middle HDI, and 54% for those with high HDI.Use of individual cohort study data yields a more complete picture of breast cancer survival in SSA than prior efforts that relied on more official datasets, such as national cancer registries. Less than half of SSA nations maintain a national cancer registry and participate in the African Cancer Registry Network, depriving researchers of a standardized and comprehensive source of local incidence and mortality data. 3 The CONCORD-3 study, for instance, only presented data from 3 SSA countries: South Africa, Nigeria, and Mauritius. 4 Even under the strict data standards applied by the CONCORD Working Group, national cancer registry data from SSA can also be incomplete and yield implausible results (eg, >95% 5-year survival for Nigerian women with breast cancer).The individual studies that Limenih et al 2 captured in their meta-analysis show a remarkable degree of heterogeneity, with the I 2 values from the 1-to 5-year survival estimates ranging from 94% to 96% and individual studies included in the 5-year survival meta-analysis reporting rates between 9% and 79%. Some of this heterogeneity could be artifactual, a byproduct of disparities in data and research quality. High-quality epidemiologic work with long-term participant follow-up is expensive and time-consuming. Even in the best of circumstances, reliance on medical record review alone leads to frequent loss to follow-up, and participants with poorer outcomes may account for a disproportionate share of missing data. It is encouraging that, while controlling for year and HDI, the authors found an association between higher-quality studies and longer survival. That finding provides some evidence against concerns that missing data and loss to follow-up have produced an overly optimistic picture of breast cancer survival in SSA. Such a range of outcomes is not necessarily surprising in a region comprising 46 countries with national per capita gross domestic produ...