Low rate of clinician-scored gynecomastia induced by 6 months of combined androgen blockade in a randomized trial: Implications for prophylactic breast irradiation.

Purpose: To determine the incidence and predictors of clinician-scored gynecomastia induced by 6 months of combined androgen blockade (CAB) in a randomized trial.

Methods: We studied 94 men with intermediate or high-risk prostate cancer randomized to radiation plus 6 months of neoadjuvant CAB consisting of a gonadotropin-releasing hormone agonist and antiandrogen (flutamide). Patients were assessed for breast symptoms monthly as per protocol. Patients reporting breast tenderness or enlargement were then examined shirtless.

Results: Median age at entry was 72.1 years. While 52 patients (55.3%) reported either breast tenderness or enlargement, only 9 patients (9.6%) were scored as having gynecomastia when examined shirtless by a single clinician. Four patients received radiation for self-reported breast tenderness or enlargement without clinician-scored gynecomastia. If these 4 had not been radiated, the total incidence of clinician-scored gynecomastia may have been as high as 13 of 94 (13.8%). No patient variable, such as age, body-mass index, and Adult Comorbidity Evaluation-27 score, or discontinuation of the antiandrogen, was associated with the development of gynecomastia.

Conclusions: While many patients self-reported breast tenderness or enlargement with short-course CAB, the incidence of breast enlargement noticeable to an examiner when the patient was shirtless was less than 15%, which is much lower than the 60% to 80% rates typically reported with antiandrogen monotherapy. Given that the long-term risks of prophylactic breast irradiation are not well characterized, these data suggest that prophylactic breast irradiation may not be as necessary in men receiving short-course CAB.