Racial comparison of receptor-defined breast cancer in Southern African women: subtype prevalence and age-incidence analysis of nationwide cancer registry data

Cancer Epidemiol Biomarkers Prev. 2014 Nov;23(11):2311-21. doi: 10.1158/1055-9965.EPI-14-0603. Epub 2014 Aug 20.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • African Continental Ancestry Group / statistics & numerical data
  • Age of Onset
  • Aged
  • Asian Continental Ancestry Group / statistics & numerical data
  • Breast Neoplasms / chemistry*
  • Breast Neoplasms / ethnology*
  • Continental Population Groups / statistics & numerical data*
  • European Continental Ancestry Group / statistics & numerical data
  • Female
  • Humans
  • Incidence
  • Middle Aged
  • Namibia / epidemiology
  • Prevalence
  • Receptor, ErbB-2 / analysis*
  • Receptors, Estrogen / analysis*
  • Receptors, Progesterone / analysis*
  • South Africa / epidemiology
  • Young Adult

Substances

  • Receptors, Estrogen
  • Receptors, Progesterone
  • ERBB2 protein, human
  • Receptor, ErbB-2