A phase II trial of docetaxel and estramustine in patients with refractory metastatic breast carcinoma

The similarity between the mechanism of action between docetaxel and estramustine generated the hypothesis of synergistic antimicrotubule effects and cytotoxicity when the two agents are combined. In addition, it has been demonstrated that estramustine binds P-glycoprotein in vitro and, thus, may prevent the efflux of taxanes in tumors that over-express P-glycoprotein. To further evaluate the combinations clinical efficacy and safety, a trial was performed in heavily pretreated patients with metastatic breast carcinoma (MBC).

Thirty-six patients with MBC were treated with estramustine 900 mg/m(2) per day divided into 3 doses given on Days 1-3 and docetaxel 70 mg/m(2) given by intravenous administration over 1 hour on Day 3 after the first dose of estramustine, every 21 days. Patients may have received any number of prior chemotherapy regimens for MBC.

Nine partial responses were observed in 31 assessable patients, for an objective response rate of 29% (95% confidence interval, 14-48%). The median progression free survival was 4 months (range, 1-41 months), and the median overall survival was 17 months (range, 2-45 months). Severe toxicities (Grade 3 or 4) were neutropenia, hypophosphatemia, and thrombosis. Seventy-five percent of patients experienced either an improvement or no change in quality of life.

The combination of docetaxel and estramustine produced responses in heavily pretreated women with MBC while maintaining quality of life.