Impact of the duration of hormonal therapy following radiotherapy for localized prostate cancer.

External-beam radiotherapy (EBRT) combined with androgen deprivation therapy (ADT) is known to provide improved survival outcomes compared with EBRT alone in the treatment of prostate cancer; however, the use of ADT has been reported to be associated with adverse events. Accordingly, the aim of the present study was to clarify the adequate duration of ADT when combined with EBRT to treat patients with high-risk localized prostate cancer, with consideration of survival outcomes and toxicity. Between 2001 and 2011, 173 patients with high-risk localized prostate cancer received ADT combined with EBRT, at a median dose of 69.6 Gy. Of these, 54 (31%) underwent short-term ADT (<36 months) and 119 (69%) underwent long-term ADT (≥36 months). During the median follow-up period of 54 months, the five-year progression-free survival rate of patients receiving short-term ADT (72.9%) was significantly lower than that of patients receiving long-term ADT (92.8%) (P<0.01). Furthermore, the incidence of cardiovascular toxicity at grade II or above was significantly higher amongst patients treated with short-term ADT compared with patients treated with long-term ADT (P<0.01). Thus, the present study determined that ADT for ≥36 months combined with EBRT significantly improved the progression-free survival of patients with high-risk localized prostate cancer and exhibited an acceptable toxicity profile.