Oestrogen and progesterone receptors as prognostic variables in hormonally treated breast cancer.

This study directly compares ER status and PgR status of primary tumour tissue measured by enzyme immunoassays for prediction of response to therapy and survival in 99 women with breast cancer treated by hormone therapy. ER and PgR status alone both correlated with response to therapy (p = 0.002 and p = 0.02 respectively), time to progression (p < 0.0001 and p = 0.003 respectively) and survival (p < 0.001 and p = 0.01 respectively). 67% of tumours ER(+)/PgR(+) showed responsive or static disease compared to 25% of tumours ER(-)/PgR(-). Tumours of mixed phenotype (i.e. ER(+)/PgR(-) and ER(-)/PgR(+)) showed an intermediate response rate of 46%. Similar findings were observed when tumour phenotype was compared with overall survival. Combining ER and PgR allows more accurate prediction of clinical outcome but does not aid in selecting individual patients for endocrine therapy.