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 ≥ 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.
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