High incidence of oestrogen receptor negative progesterone receptor positive phenotype in Indian breast cancer: fact or fiction?

The incidence of oestrogen receptor negative and progesterone receptor positive (ER-/PR+) invasive breast carcinoma is reported to be as high as 21% in India, as compared to 3-5% in the western literature. We used automated immunohistochemistry with Biogenex antibodies to re-evaluate the ER status in 37 Indian patients with invasive breast carcinomas previously reported as ER-/PR+ by a different manual staining protocol in two city hospitals. The automated technique utilized different reagents (all US FDA approved for in vitro diagnostic use) and staining protocols from those used in the manual assays. Of the 37 previously ER-tumours, only 9 (24.3%) tumours remained ER-. Twenty-eight (75.6%) tumours were found to be ER+. Our results indicate that the high incidence of ER-/PR+ breast cancer reported from India is most likely due to the use of suboptimal manual assays, rather than true genetic differences. ER expression in breast cancer among Indian women may be much higher than previously believed. These results have important implications for the use of oestrogen modulators such as tamoxifen in developing countries such as India.