We determined the risk of recurrence in men enrolled on a randomized trial for prostate cancer who were treated with radiation therapy (RT) alone or in conjunction with combined or less than combined androgen suppression therapy (AST).

Between 1995 and 2001, 206 men with localized but unfavorable-risk adenocarcinoma of the prostate were randomly assigned to receive RT or RT and AST, which was defined as 6 months of both a luteinizing hormone-releasing hormone agonist and an antiandrogen. A post-random assignment hypothesis that was generated by multivariable Cox regression analyses was used to evaluate whether the risk of prostate-specific antigen (PSA) recurrence was significantly associated with months of antiandrogen use; regression analysis adjusted for known prognostic factors, comorbidity score, and medications that can elevate liver function tests sufficiently to necessitate discontinuation of the antiandrogen.

After a median follow-up of 8.2 years (interquartile range,7.0 to 9.5 years), 81 men sustained PSA recurrence. An increasing PSA level (P < .001); Gleason score of 8, 9, or 10 (P < .001); and clinical category T2 disease (P = .005) were significantly associated with an increased risk of recurrence. However, recurrence risk was significantly decreased (adjusted hazard ratio, 0.81; 95% CI, 0.72 to 0.92; P = .001) with each additional month of antiandrogen use after analysis was adjusted for these known prognostic factors.

Men with localized but unfavorable-risk prostate cancer who were treated with RT and 6 months of planned combined AST appear to have an increased risk of recurrence when treated with less than as compared with 6 months of the antiandrogen.