Fadrozole hydrochloride in postmenopausal patients with metastatic breast carcinoma

Abstract

Background: Fadrozole hydrochloride (CGS-16949A) belongs to the class of aromatase inhibitors that lowers circulating estrogen levels by inhibiting the conversion of androgens to estrogens, thereby causing tumor regression in patients with breast carcinoma.

Methods: This was a prospective, randomized, Phase II study of fadrozole hydrochloride in postmenopausal patients with metastatic breast carcinoma. The three treatment groups received, respectively, fadrozole hydrochloride 0.6 mg three times daily, 1 mg twice daily, and 2 mg twice daily orally.

Results: Fifty-six patients were entered on protocol and 54 were eligible (2 patients were perimenopausal). Eight patients had received no prior therapy, 15 patients had received prior hormonal therapy, 5 patients had received prior chemotherapy, and 28 patients had received both. After 12 weeks of treatment, 2 complete and 3 partial responses were observed. Forty patients continued treatment beyond 12 weeks, and 3 additional responses were achieved. Thus, 8 of 56 patients responded (14% overall response rate). Responses did not appear to be dose-related. The median duration of response was 36 months (range, 8-45 months). Subjective toxicity was mild to moderate and appeared more frequent on the 2 mg twice daily dosing schedule. No objective toxicity in laboratory parameters was observed. No patient had severe or life-threatening toxicity. Fadrozole hydrochloride plasma concentrations (obtained every 2 weeks for 12 weeks) appeared to be dose-dependent and noncumulative.

Conclusions: This study confirms modest activity of fadrozole hydrochloride in a heterogeneous group of patients with breast carcinoma treated at three different dose levels.