Androgen Deprivation Therapy Use in the Setting of High-dose Radiation Therapy and the Risk of Prostate Cancer–Specific Mortality Stratified by the Extent of Competing Mortality

Abstract

The addition of androgen deprivation therapy (ADT) to radiation therapy (RT) is the standard of care for men with intermediate- and high-risk prostate cancer (PC). However, whether competing mortality (CM) affects the ability of ADT to improve, survival remains unanswered. We calculated a CM risk score using a Fine-Gray semiparametric model that included age and cardiometabolic comorbidities from a cohort of 17,669 men treated with high-dose RT with or without supplemental ADT for nonmetastatic PC. Fine and Gray competing risk regression analysis was used to assess whether ADT reduced the risk of PC-specific mortality for men with a low versus a high risk of CM among the 4550 patients within the intermediate- and high-risk cohort after adjustment for established PC prognostic factors, year of treatment, site, and ADT propensity score. After a median follow-up of 8.4years, 1065 men had died, 89 (8.36%) of PC. Among the men with a low CM score, ADT use was associated with a significant reduction in the risk of PC-specific mortality (adjusted hazard ratio 0.35, 95% confidence interval 0.14-0.87, P=.02) but was not for men with high CM (adjusted hazard ratio 1.33, 95% confidence interval 0.77-2.30, P=.30). Adding ADT to high-dose RT appears to be associated with decreased PC-specific mortality risk in men with a low but not a high CM score. These data should serve to heighten awareness about the importance of considering competing risks when determining whether to add ADT to RT for older men with intermediate- or high-risk PC.