Estramustine phosphate sodium in heavily pretreated patients with metastatic breast cancer: a retrospective consecutive case series

Background: Estramustine phosphate sodium (EMP) is an oral agent poorly developed—although active—in patients with metastatic breast cancer (MBC). To resume interest in EMP in MBC, we analyzed a retrospective series of consecutive patients with estrogen receptor-positive disease. Methods: EMP was given orally at a dose of 140 mg daily. Treatment discontinuation rates due to progressive disease/toxicity and response rates were assessed. Results: Twenty postmenopausal patients with mainly visceral disease were treated with EMP, in five cases in combination with other anticancer drugs. Median numbers of previous chemotherapies and hormonal treatments were six and four, respectively. From the entire cohort, one complete response and four partial responses were observed. The proportions of patients free of progression at 6 and 12 months were 39 and 8 %, respectively. Six patients discontinued EMP, three each for toxicity and adverse events. Conclusion: Good disease control was obtained in heavily pretreated MBC patients receiving EMP. Toxicity was manageable and reversible although treatment discontinuation has to be considered. A prospective study should be encouraged to identify the optimal use of the drug.