Receptor-Defined Breast Cancer in Five East African Countries and Its Implications for Treatment: Systematic Review and Meta-Analysis

PURPOSE: Estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor-2 (HER2) are determinants of treatment and mortality for patients with breast cancer (BC). In East Africa, the estimated 5-year survival (37.7%) is far lower than the US average (90%). This meta-analysis investigates BC receptor subtypes within five East African countries to ascertain cross-country patterns and prioritize treatment needs. METHODS: From a PubMed search, January 1, 1998-June 30, 2019, for all English-only BC articles for Ethiopia, Kenya, Rwanda, Tanzania, and Uganda, eligible studies had receptor distributions for female BC samples ≥ 30 patients. Outcomes were proportions of ER+, PR+, and HER2-positive (HER2+), and/or molecular subtypes. Data included study characteristics and mean or median patient age. Using metaprop, Stata 16, we estimated pooled proportions (ES) with 95% CIs and assessed heterogeneity. RESULTS: Among 36 BC studies with receptor data, 21 met criteria. Weighted mean age was 47.5 years and median, 48. Overall ES were as follows: 55% for ER-positive (ER+) (95% CI, 47 to 62), 23% for HER2+ (95% CI, 20 to 26), and 27% for triple-negative BC (TNBC) (95% CI, 23 to 32). CONCLUSION: We found differences between countries, for example, lower distribution of TNBC in Ethiopia (21%) compared with Uganda (35%). ER+, the dominant BC subtype overall at 55%, emphasizes the need to prioritize endocrine therapy. Overall proportions of HER2+ BC (with or without ER+ or PR+), 23%, approached proportions of TNBC, 27%, yet HER2 testing and treatment were infrequent. Testing and reporting of receptor subtypes would promote delivery of more effective treatment reducing the mortality disparity.