2alpha, 3alpha-epithio-5alpha-androstan-17beta-yl 1-methoxycyclopentyl ether in the treatment of advanced breast cancer: Japanese Cooperative Group of Hormonal Treatment for Breast Cancer.

A new antiestrogenic steroid, 2alpha, 3alpha-epithio-5alpha-androstand-17beta-yl 1-methoxy-cyclopentyl ether, mepitiostane, given orally 10 mg b.i.d. to 50 patients with advanced breast cancer, produced objective regression of the tumor in 17 cases (34%). Objective regression of the metastases was seen in 20 of the 48 control patients given fluoxymesterone, 10 mg b.i.d. orally (47.7%). These figures do not differ significantly. The study was a prospective, randomized, double-blind trial employing the protocol of the Cooperative Breast Cancer Group. There was a significantly lower incidence of hepatotoxicity in the patients given mepitiostane.