Poor hormone receptor expression in East African breast cancer: Evidence of a biologically different disease?

Background: Few studies have examined breast cancer hormone receptor expression in Africans. We report on the hormone receptor profile of breast cancer in East Africans in the largest prospective study for this region. Methods: Consecutive breast cancer presentations to a hospital in Kijabe (2001-2007) were included. Demographic, clinical, and test data were collected. ER/PR and Her2 testing was based on immunohistochemistry (IHC). Results: There were 129 subjects (median 47 years), most had invasive ductal cancer and locally advanced disease and/or metastases. ER/PR testing was done in 120: 24% had ER-positive tumours, 34% were ER- and/or PR-positive, 10% were ER-negative but PR-positive tumours, and 66% were negative for ER and PR. ER/PR positivity was not associated with stage (P = 0.28) and was not related to age, parity, menopausal status, or node metastases. Increasing tumour grade was associated with PR expression (P = 0.02) with decreasing frequency of PR positive tumours as histological grade increased; there was weak evidence of an association between grade and ER expression (P = 0.06). Of cases tested, 26.5% overexpressed Her2. Conclusions: Breast cancer in Kijabe is an advanced-stage disease, comprised mainly of poorly differentiated cancers that are less likely to be hormone sensitive (across all stages of disease). ER/PR testing of all those affected by breast cancer should be supported as a global priority in cancer control. International and inter-African research collaborations are needed to allow genetic detailing of tumours in indigenous Africans to assess possible racial heterogeneity in the biology of breast cancer.