Advanced breast cancer: response to high dose oral medroxyprogesterone acetate.

We treated 105 patients with advanced breast cancer, using the progestational agent medroxyprogesterone acetate (MPA), 200 mg orally tds in a non-randomised trial. In general they were a poor risk population, since 78 had received prior endocrine therapy (21 more than one type) and 58 prior chemotherapy. Treatment was well tolerated. Side effects included weight gain, muscle cramps, fine tremor and fluid retention, but these were usually mild, resolved if the dose of drug was reduced, and only one patient stopped treatment because of toxicity. Seventeen patients died within six weeks of starting MPA, and disease progression occurred in a further 58. Nine have had stable disease for periods ranging from two to 11 months, and there were 21 who showed disease regression. Response to treatment continues in 13 of these patients, and at the time of writing the median duration of response is 10 months. Response rates were similar in pre- and post-menopausal patients. The dose of MPA was double to 400 mg tds in 16 patients whose disease had progressed on 200 mg tds, but no additional responses were seen in this group. Seven out of 24 (29%) patients who had not received prior endocrine therapy responded to high dose oral MPA, a response rate similar to that seen following other hormonal manipulations, but because the drug also has activity against hormone-resistant tumours and is well tolerated, it should have role in the treatment of advanced breast cancer.