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.

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 8.4 years, 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.

International journal of radiation oncology, biology, physics. 2016 Aug 22 [Epub]

Brent S Rose, Ming-Hui Chen, Jing Wu, Michelle H Braccioforte, Brian J Moran, Daniel E Doseretz, Michael J Katin, Rudolf H Ross, Sharon A Salenius, Anthony V D'Amico

Harvard Radiation Oncology Program, Brigham and Women's Hospital/Dana-Farber Cancer Institute, Boston, Massachusetts. Electronic address: ., Department of Statistics, University of Connecticut, Storrs, Connecticut., Prostate Cancer Foundation of Chicago, Westmont, Illinois., 21st Century Oncology, Inc, Fort Myers, Florida., Department of Radiation Oncology, Brigham and Women's Hospital/Dana-Farber Cancer Institute, Boston, Massachusetts.