Fadrozole hydrochloride in postmenopausal patients with metastatic breast carcinoma

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.

[A combined effect of fadrozole and tamoxifen in postmenopausal patients with recurrent breast cancer: a preliminary report: Japanese Cooperative Study Group of Fadrozole and Tamoxifen]

To elucidate the combined effects of fadrozole (nonsteroidal aromatase inhibitor) and tamoxifen, 11 postmenopausal patients with recurrent breast cancer were examined between October 1996 and June 1998. One patient, 49 years old, was ineligible due to the short period after castration. The patients were aged 53-71 years (mean 63.5). PS was 0-1. Six patients were pre-treated with tamoxifen and 6 with oral 5-FU derivatives. One had no previous treatment. The target lesions were soft tissues in 5, bone in 4, lungs in 6 and liver in 1. The response was CR in 2, PR in 2, SD (longer than 24 weeks) in 2, NC in 1 and PD in 3. Consequently, the response rate was 60% (6 out of 10 eligible cases). Hormonal concentration was measured before and after administration of two drugs in weeks 2, 4, 6, 8 and at the end of the treatment, and significant decreases in estrogens in peripheral blood were observed. Adverse effects (4 cases of low grade headache, dizziness and elevation of GOT, GPT, gamma-GTP) did not influence the continuous administration of the drugs. We conclude that combined administration of fadrozole (2nd generation aromatase inhibitor) and tamoxifen produces a good response in postmenopausal recurrent breast cancer patients, and can be a useful treatment for patients with breast cancer.

Antitumor and endocrine effects of an aromatase inhibitor (CGS 16949A) on DMBA-induced rat mammary tumor

The antitumor and endocrine effects of a new nonsteroidal aromatase inhibitor were studied using DMBA-induced rat mammary carcinomas. CGS 16949A (CGS) was administered orally once daily for 3 weeks. A marked antitumor effect was noted at doses of more than 1 mg/kg, and weight gain was dose dependent. Histologic examination showed atrophic changes of the tumors and decreased expression of estrogen receptor levels. To investigate the mechanism of the antitumor effect of CGS, we studied the changes in endocrine function in rats given this agent. In the groups receiving more than 1 mg/kg of CGS, the serum estradiol and prolactin levels were lower and the serum luteinizing hormone level was higher than in the control group. In rats treated with CGS, ovary weight was increased, while uterus and pituitary weights were decreased. These changes were dose dependent. In contrast, the serum corticosterone level and adrenal weight remained unchanged. We conclude that CGS inhibits the growth of hormone-dependent tumors by changing the hormonal environment.