High-dose megestrol acetate in the treatment of postmenopausal women with advanced breast cancer.

The optimal dose of progesterone compounds for the treatment of breast cancer is unknown, but there is evidence to suggest a dose-response curve. We are testing the tolerability and efficacy of megestrol acetate administered orally and continuously in doses three to ten times higher than the standard dose of 160 mg/d. We have so far treated 33 patients with metastatic breast cancer and positive or unknown tumor hormone receptor status. Thirty patients had had documented disease progression with previous hormonal therapy, and 22 had failed with previous chemotherapy. Twenty-five patients had objectively measurable metastases. In this heavily pretreated group, the objective response rate was 40%; in addition, 32% of patients had stabilization of disease. Interestingly, ten of 12 patients who had developed disease progression while on standard-dose megestrol acetate therapy had objective response or stabilization on the higher dose. Toxicity was acceptable and reversible and included mild elevations of blood pressure and weight gain. Our results indicate that high-dose megestrol acetate is well-tolerated and highly active in advanced refractory breast cancer, and suggest a dose-response curve for the drug in the treatment of breast cancer.