Sequential combination of tamoxifen and high dose medroxyprogesterone acetate: therapeutic and endocrine effects in postmenopausal advanced breast cancer patients.

A sequential combination of tamoxifen and medroxyprogesterone acetate has been evaluated in 42 postmenopausal untreated patients with metastatic breast cancer. Patients received tamoxifen 10 mg b.i.d., days 1-14, followed by medroxyprogesterone acetate 500 mg b.i.d., days 15-28, orally in an alternating sequence until progression. Twenty-two out of 40 evaluable patients showed an objective response to treatment (55%, 95% confidence limits 38-75%). A significantly higher response rate was observed in patients with age greater than or equal to 70 years, with soft tissue dominant lesions and with only one metastatic site. Median time to progression was 41 weeks and the median survival time 88 weeks. In 4 cases treatment was discontinued because of severe toxicity while in the remaining patients no toxicity (20 patients) or mild side effects (17 patients) have been observed. After 2 months of therapy, this combination showed a progestogenic effect on the endocrine parameters inducing a significant decrease of SHBG, gonadotropins, testosterone and cortisol. These preliminary clinical results and the moderate toxicity of the sequential combination support the need to further investigate this approach.