Estrogen receptor expression and docetaxel efficacy in patients with metastatic breast cancer: A pooled analysis of four randomized trials

1046 Background:Differences in the efficacy of various chemotherapies in patients with estrogen receptor (ER) positive metastatic breast cancer are not well understood. In the present study, we assessed the efficacy of docetaxel in patients with metastatic breast cancer according to ER expression.Methods: The efficacy of docetaxel on response rates and progression-free survival were analyzed according to ER expression in four randomized trials that included a total of 1,631 patients. Odds-ratio for tumor response was estimated with logistic regression and hazard ratio for progression-free survival was estimated with Cox proportional hazards models. Results: ER expression was assessable in 1,037 patients included in these trials (64%). ER was expressed in 601 tumors (58%). Overall, docetaxel was associated with an increased response rate (odds ratio: 2.66, 95% CI: 1.83 to 3.87) and decreased hazard of disease progression (hazard ratio: 0.85, 95% CI: 0.73 to 0.97) compared to non-docetaxel containing therap...