Adjuvant endocrine therapy for operable breast cancer using the antiestrogen mepitiostane: a preliminary report.

The steroidal antiestrogen, mepitiostane (Thioderone, 2 alpha, 3 alpha-epitio-5 alpha-androstane-17 beta-yl 1-methoxycyclopentyl ether) was administered orally to 182 patients with operable breast cancer as an adjuvant therapy after mastectomy intermittently for 3 years. The mean duration of follow-up was 32 months (6 approximately 42 months). The treatment failure ratio and the time distribution of failure among those given mepitiostane were compared with those of 96 patients treated with mitomycin C. There was a recurrence of malignancy in 11.5% (21/182) of patients treated with mepitiostane and in 15.6% (15/96) of patients given mitomycin C. The recurrence rates of the postmenopausal patients treated with mepitiostane and those treated with motomycin C were 3.8% (3/80) and 17.6% (18/102), respectively. In contrast, the malignancy relapsed in 24.0% (14/39) and in 2.4% (1/42) of the premenopausal patients given mepitiostane and those given mitomycin C, respectively. Estrogen and progestrone receptors (ER, PgR) were assayed in some of the primary breast cancers. Although there was no difference in recurrence rate between the ER-positive and -negative cases, the recurrence rate of the patients with ER(+)PgR(+) tumors treated with mepitiostane was shown to be lower than those with ER(+)PgR(-) or ER(-)PgR(-) tumors. The antiestrogen mepitiostane may thus be useful in postmenopausal patients, in whom the adjuvant chemotherapy was less effective in preventing the recurrence of malignancy.