Prostate cancer-specific mortality after definitive radiation therapy: Who dies of disease?

Background: A competing risks analysis was undertaken to identify subgroups at greatest risk of dying from prostate cancer (PC) after definitive external beam radiation therapy (RT) ± androgen deprivation therapy (ADT) in the prostate specific antigen (PSA) era. Methods: Outcomes of 2675 men with localised PC treated with RT ± ADT from 1987-2007 were analysed. Prostate cancer-specific mortality (PCSM) and non-PCSM rates were calculated after stratifying patients according to National Comprehensive Cancer Network (NCCN) risk-group, RT dose, use of ADT and age at treatment. Results: Only 0.2% of low-risk men died of PC 10 years after treatment. All of these deaths occurred in patients treated with <72 Gy, and only one patient ≥70 years old who received ≥72 Gy died of PC at last follow-up. Likewise, none of the patients with intermediate-risk disease treated with ≥72 Gy and ADT died of PC at 10 years, and the highest 10-year rate of PCSM was seen in men ≥70 years old treated with <72 Gy without ADT (5.1%). Among high-risk men <70 years old, treatment with RT dose <72 Gy without ADT yielded similar 10-year rates of PCSM (15.2%) and non-PCSM (18.5%), whereas men treated with ≥72 Gy and ADT were twice as likely to die from other causes (16.2%) than PC (9.4%). In high-risk men ≥70 years old, dose-escalation with ADT reduced 10-year PCSM from 14% to 4%, and most deaths were due to other causes. Conclusion: Low- and intermediate-risk patients treated with definitive RT are unlikely to die of PC. PCSM is higher in men with high-risk disease but may be reduced with dose-escalation and ADT, although patients are still twice as likely to die of other causes.