Determinants of Prostate Cancer–Specific Survival After Radiation Therapy for Patients With Clinically Localized Prostate Cancer

Abstract

PURPOSE: Identifying pretreatment and posttreatment predictors of time to prostate cancer–specific death (PCSD) after external-beam radiation therapy (RT) was the subject of this study. PATIENTS AND METHODS: A Cox regression analysis was used to evaluate the ability of the pretreatment risk group to predict time to PCSD for 381 patients who underwent RT for clinically localized prostate cancer. Posttreatment factors analyzed for the 94 patients who experienced prostate-specific antigen (PSA) failure included the time to PSA failure, the posttreatment PSA doubling time (DT), and the timing of salvage hormonal therapy. RESULTS: Despite the median age of 73 years at diagnosis, 45% of patients with high-risk disease were estimated to die from prostate cancer within 10 years after RT compared with 0% (P = .004) and 6% (P = .05) for patients with low- or intermediate-risk disease, respectively. Predictors of time to PCSD after PSA failure included PSA DT (P = .01) and delayed use of hormonal therapy (P ≤ .002). Nearly identical estimates of PCSD and all-cause death after PSA failure were noted for patients with a short PSA DT (ie, ≤ 12 months). CONCLUSION: Prostate cancer was a major cause of death during the first decade after RT for patients with clinically localized but high-risk disease, and the cause of death for patients with a short PSA DT after RT was nearly always prostate cancer. These data provide evidence to propose the hypothesis that a short posttreatment PSA DT may serve as a possible surrogate for PCSD. Prospective validation is needed.