Tamoxifen for flutamide/finasteride-induced gynecomastia

Current therapies for advanced prostate carcinoma lead to a marked decrease in serum testosterone levels, which renders patients impotent. In preliminary studies, combination therapy with flutamide and finasteride has been used as an alternative therapy for the treatment of prostate carcinoma because potency can be preserved. Both of these agents can cause gynecomastia and breast/nipple tenderness.

Six men being treated for advanced prostate carcinoma with flutamide/finasteride combination therapy developed painful gynecomastia, which was treated with tamoxifen 10 to 30 mg/day for 1 month. Clinical follow-up included breast measurements and determination of prostate-specific antigen (PSA), testosterone, and estradiol levels.

While on this combination therapy for prostate carcinoma, 4 of 6 patients experienced a decrease in PSA level to less than 0.5 ng/mL. All patients remained potent. Serum testosterone increased in each patient who had a baseline level drawn. Estradiol levels were noted to be elevated in 4 of 6 patients at the time of evaluation for gynecomastia. After treatment with tamoxifen, circulating estradiol levels increased in 3 patients from 1.3 to 2.2 times the baseline level. Five patients experienced complete resolution of breast and nipple pain on tamoxifen 10 mg/day within the first month. The other patient had to be treated with 30 mg/day for 1 additional month, which subsequently resulted in pain resolution.

These preliminary results suggest that low-dose tamoxifen is useful in treating painful gynecomastia for those patients on flutamide/finasteride combination therapy for advanced prostate carcinoma.