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 suppression therapy (AST) is used to treat men with clinically localized adenocarcinoma of the prostate, but outcome using this combined therapy compared with RT alone is not known. Objective To determine the relative efficacy of RT plus AST vs RT alone among men with clinically localized prostate cancer. Design, Setting, and Patients Retrospective cohort study of 1586 men with prostate 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 Radiology 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 not statistically different among low-risk patients (P = .09), whereas intermediate- and high risk patients treated with RT plus AST had significantly better outcomes than those treated with RT alone (P < .001 and = .009, respectively). 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 for men with clinically localized prostate cancer in intermediate- and high-risk groups treated with RT plus AST vs those treated with RT alone. Results from prospective randomized trials currently under way are needed to validate these findings.