Biochemical outcome following external beam radiation therapy with or without androgen suppression therapy for clinically localized prostate cancer

Context Combined treatment using radiation therapy (RT) and androgen suppre ssion therapy (AST) is used to treat men with clinically localized adenocar cinoma of the prostate, but outcome using this combined therapy compared wi th RT alone is not known. Objective To determine the relative efficacy of RT plus AST vs RT alone amo ng men with clinically localized prostate cancer. Design, Setting, and Patients Retrospective cohort study of 1586 men with p rostate cancer who were treated between January 1989 and August 1999 using 3-dimensional conformal RT with (n = 276) or without (n = 1310) 6 months of AST. Main Outcome Measure Relative risk (RR) of prostate-specific antigen (PSA) failure (defined according to the American Society for Therapeutic Radiolog y and Oncology consensus statement), by treatment and high-, intermediate-, or low-risk group based on serum PSA level, biopsy Gleason score, and 1992 American Joint Commission on Cancer clinical tumor category. Results Estimates of 5-year PSA outcome after RT with or without AST were n ot statistically different among low-risk patients (P = .09), whereas inter mediate- and high risk patients treated with RT plus AST had significantly better outcomes than those treated with RT alone (P < .001 and = .009, resp ectively). The RR of PSA failure in low-risk patients treated with RT plus AST was 0.5 (95% confidence interval [CI], 0.3-1.1) compared with patients treated with RT alone. The RRs of PSA failure in intermediate-risk and high -risk patients treated with RT plus AST compared with RT alone were 0.2 (95 % CI, 0.1-0.3) and 0.4 (95% CI, 0.2-0.8), respectively. Conclusions Our data suggest a significant benefit in 5-year PSA outcomes f or men with clinically localized prostate cancer in intermediate- and high- risk groups treated with RT plus AST vs those treated with RT alone. Result s from prospective randomized trials currently under way are needed to vali date these findings.