Breast cancer receptor subtypes in East Africa: A systematic review and meta-analysis.

Abstract

e19074 Background: Estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2) are determinants of both treatment and mortality for patients with breast cancer (BC). With a mortality to incidence ratio of 0.51, mortality rates for breast cancer in East Africa are among the world’s highest. Building on a meta-analysis of BC receptor subtypes in sub-Saharan Africa (2014) and including all recently available PubMed literature, our meta-analysis aims to investigate the differences among receptor subtype distribution in five East African countries. Methods: Receptor distributions for female samples >30 in all BC articles for Ethiopia, Kenya, Rwanda, Tanzania and Uganda were obtained from PubMed, January 1, 1998 - June 30, 2019. Outcomes were proportions of ER+, PR+, and HER2+ and/or molecular subtypes. Data included study characteristics and mean/median patient age (weighted by observations). Using metaprop for STATA 16, we estimated pooled proportions (ES) with 95% confidence intervals (CI) and assessed I2 statistics for heterogeneity across studies. Results: Among 35 BC studies with receptor data, 21 met criteria. Overall, the weighted mean age was 47.5 years (SD 3.2) and median, 48. For ER+ (18 studies/n=2,875), the overall ES was 0.55 (95% CI 0.47, 0.62), I2 of 94.4%, p<0.001, ranging from 0.62 in Ethiopia (95% CI 0.52, 0.72) to 0.42 in Uganda (95%0.36, 0.49). For HER2+ (18 studies/n=2,689), the overall ES was 0.23 (95% CI 0.20, 0.26), I2 of 70.2%, p<0.001, and ranged from 0.27 in Ethiopia (95% CI 0.18, 0.36) to 0.21 in both Tanzania and Uganda (95% CI 0.13/0.14, 0.28). For triple negative (TN, 15 studies/n=2,510), the overall ES was 0.28 (95% CI 0.23, 0.32), I2 of 84.0%, p<0.001, varying from 0.21 in Ethiopia (95% CI 0.15, 0.27) to 0.46 in Tanzania (95% CI 0.32, 0.60). Conclusions: We found differences between countries, e.g. lower distribution of TN in Ethiopia (21%) compared to Uganda (35%) and Tanzania (46%), and high between-study heterogeneity. Consistent with former studies, ER+, 55%, was the dominant subtype, particularly in Ethiopia, Kenya and Rwanda, indicating the need to prioritize hormonal treatment. Overall rates of HER2 subtype, 23%, approached overall rates of TN, 28%, yet HER2 testing is often not performed due to the cost and unavailability of anti-HER2 therapy, hence this subtype often goes untreated. These findings highlight the benefit of testing and reporting of receptor subtypes at the country level to promote delivery of more effective treatment to reduce the mortality disparity.