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Background: Receptor-defined breast cancer proportions vary across Africa. They have important implications for survival prospects and research priorities.Methods: We studied estrogen receptor (ER), progesterone receptor (PR), and HER2 receptor statuses in two multiracial Southern African countries with routine diagnostic immunohistochemistry. A total of 12,361 women with histologically confirmed breast cancer diagnosed at age ≥20 years during (i) 2009–2011 from South Africa's national cancer registry (public sector) and (ii) 2011–2013 from Namibia's only cancer hospital were included. Crude, age, and age + laboratory–adjusted ORs of receptor status were analyzed using logistic regression, and age–incidence curves were analyzed using Poisson regression.Results: A total of 10,047 (81%) women had known ER status. Ranking of subtypes was consistent across races: ER+/PR+HER2− was most common (race-specific percentage range, 54.6%–64.8%), followed by triple-negative (17.4%–21.9%), ER+/PR+HER2+ (9.6%–13.9%), and ER−PR−HER2+ (7.8%–10.9%). Percentages in black versus white women were 33.8% [95% confidence (CI), 32.5–35.0] versus 26.0% (24.0–27.9) ER−; 20.9% (19.7–22.1) versus 17.5% (15.4–19.6) triple-negative; and 10.7% (9.8–11.6) versus 7.8% (6.3–9.3) ER−PR−HER2+. Indian/Asian and mixed-ancestry women had intermediate values. Age–incidence curves had similar shapes across races: rates increased by 12.7% per year (12.2–13.1) across ER subtypes under the age of 50 years, and thereafter slowed for ER+ (1.95%) and plateaued for ER− disease (−0.1%).Conclusions: ER+ breast cancer dominates in all Southern African races, but black women have a modest excess of aggressive subtypes.Impact: On the basis of the predominant receptor-defined breast tumors in Southern Africa, improving survival for the growing breast cancer burden should be achievable through earlier diagnosis and appropriate treatment. Cancer Epidemiol Biomarkers Prev; 23(11); 2311–21. ©2014 AACR. |
