Prostate Cancer-Specific Mortality After Definitive Radiation Therapy: Who Dies Of Disease?

181 Background: A competing risks analysis was undertaken to identify patient subgroups at greatest risk of dying from prostate cancer (CAP) after treatment with definitive external beam radiation therapy (RT) +/− androgen deprivation therapy (ADT) in the PSA era, and to determine which factors predict for survival from disease. Methods: A total of 2,675 men with localized CAP treated with RT +/− ADT at M. D. Anderson Cancer Center from 1987-2007 were evaluated. Prostate cancer-specific mortality (PCSM) and other cause mortality rates were calculated after stratifying patients according to NCCN risk group, RT dose, use of ADT, and age at treatment. In total, 21% had low-risk, 40% had intermediate-risk, and 39% had high-risk disease. Multivariate analysis (MVA) was performed using Cox regression modeling. Results: Median age was 68.5 years and median follow-up was 6.4 years. For patients with low-risk disease, only 0.2% died of CAP 10 years after treatment. None of the low-risk patients <70 years old who received ≥72 Gy died of CAP. The majority of deaths in the intermediate-risk group were also due to other causes; men ≥70 years old who received <72 Gy had the highest 10-year PCSM (5%). High-risk patients <70 years old who received <72 Gy without ADT had similar 10-year rates of CAP (15.2%) and non-CAP (18.5%) mortality. Men with high-risk disease <70 years old treated with higher doses >72 Gy were twice as likely to die from non-CAP causes (15.9%) than die from CAP (8.6%). In older men ≥70 years old with high risk disease, dose-escalation with ADT reduced 10-year PCSM from 14% to 4%, and most deaths were due to other causes (41% and 20%). On MVA, dose (p=0.002), ADT (p=0.007), PSA (p<0.0001) and Gleason score (p<0.0001) were predictive of PCSM in the high-risk group. Conclusions: Men with low- and intermediate-risk CAP treated with definitive RT are unlikely to die of disease. PCSM is higher in men with high-risk disease but can be reduced with dose escalation and ADT, although patients are still twice as likely to die of other causes. No significant financial relationships to disclose.