Tamoxifen is more effective than radiotherapy at preventing gynecomastia and breast pain in men with prostate cancer, according to trial results published online April 13th by Lancet Oncology.

The drug bicalutamide has been licensed in some European countries as adjuvant therapy to surgical prostate removal or radiotherapy for early prostate cancer. Gynecomastia and breast pain are common side effects of bicalutamide therapy and can cause some patients to withdraw from treatment. Because early withdrawal from treatment may compromise outcome, effective management strategies for these complications are needed. Currently, the most commonly used preventive treatment is low-dose radiotherapy. Trials have suggested that preventative treatment with anti-estrogen drugs such as tamoxifen could also be effective.

Giuseppe Di Lorenzo, MD, and his Italian colleagues conducted a clinical trial to compare the effectiveness of tamoxifen with that of electron-beam radiotherapy for prevention and treatment of gynecomastia and breast pain caused by bicalutamide therapy. They recruited 151 men who had received primary treatment for prostate cancer between January 2002 and February 2004. Roughly one third (51) of patients were randomized to 150 mg bicalutamide per day, 50 patients to 150 mg bicalutamide per day and 10 mg tamoxifen per day for 24 weeks, and 50 patients to 150 mg bicalutamide per day and one dose of radiotherapy at the start of treatment.

Patients were followed for an average of 25 months. The investigators found that 35 of the 51 (70 percent) patients assigned to bicalutamide alone developed enlarged breasts compared with 4 of 50 (8 percent) assigned bicalutamide and tamoxifen and with 17 of 50 (34 percent) assigned bicalutamide and radiotherapy. Of 51 patients on bicalutamide only, 29 developed breast pain compared with 3 of 50 receiving additional tamoxifen and 15 of 50 receiving radiotherapy.

The 35 patients assigned to bicalutamide only who subsequently developed breast enlargement or had moderate to severe breast pain were randomized to 10mg tamoxifen or one dose of radiotherapy. In this subgroup, tamoxifen substantially reduced the frequency of breast enlargement and pain compared with radiotherapy. The treatments were well tolerated and the groups did not differ in quality of life or relapse-free survival.

Dr Di Lorenzo concluded: “We have shown that tamoxifen and radiotherapy can prevent breast enlargement and breast pain in some patients receiving bicalutamide therapy for prostate cancer, and that tamoxifen is more effective than radiotherapy.”