UC San Diego

PURPOSE: The survival benefit of combined radiation therapy (RT) and androgen deprivation therapy (ADT) compared with ADT alone for clinically lymph node-positive prostate cancer remains controversial. METHODS AND MATERIALS: We identified patients with clinically node-positive, nonmetastatic prostate cancer diagnosed between 2000 and 2015 and treated with ADT (n = 450) or ADT-RT (n = 198) from a national Veterans Affairs database. We compared prostate cancer-specific mortality (PCSM) and all-cause mortality (ACM) between treatment groups using multivariable competing-risks regression and Cox regression, respectively. An interaction term between ADT-RT and prostate-specific antigen (PSA) level (dichotomized about the median) was included in the multivariable models. RESULTS: ADT-RT was associated with improved PCSM among patients with PSA levels less than the median of 26 ng/mL (sub-distribution hazard ratio, 0.50; 95% confidence interval [CI] 0.28-0.88; P = .02) but not greater than the median (hazard ratio [HR], 1.15; 95% CI 0.67-1.96; P = .62) (P = .038 for interaction). ADT-RT was also associated with improved ACM among patients with PSA levels less than the median (HR, 0.38; 95% CI 0.25-0.57; P < .001) but not greater than the median (HR, 0.91; 95% CI 0.60-1.38; P = .66) (P = .004 for interaction). CONCLUSIONS: Definitive treatment with ADT-RT is associated with improved PCSM and ACM among patients with clinically node-positive prostate cancer and lower baseline PSA levels. Patients with clinically node-positive disease appear to be a heterogeneous cohort, with a subset who may achieve long-term survival with combined RT and ADT.