Elective Pelvic Lymph Node Radiation Therapy and the Risk of Death in Patients With Unfavorable-Risk Prostate Cancer: A Postrandomization Analysis

Abstract

PURPOSE Although a contemporary randomized clinical trial has led to the use of whole-pelvic radiation therapy (WPRT), long-term data evaluating a potential reduction in mortality are lacking and are addressed in the current study. MATERIALS AND METHODS From 2005 to 2015, 350 men with localized, unfavorable-risk prostate cancer (PC) were randomly assigned to receive androgen deprivation therapy (ADT) and RT plus docetaxel versus ADT and RT. Treatment of the pelvic lymph nodes was at the discretion of the treating physician. Multivariable Cox and Fine and Grays regression analyses were performed to assess whether a significant association existed between radiation treatment volume and all-cause mortality (ACM) and PC-specific mortality (PCSM), respectively, adjusting for known PC prognostic factors and comorbidity. An interaction term between age (categorized by dichotomization at 65 years to enable clinical interpretation and applicability of the results and which approximates the median (66 years [IQR, 61-70]) and radiation treatment volume was included in the analysis. RESULTS After a median follow-up of 10.20 years (IQR, 7.96-11.41), 89 men died (25.43%); of these, 42 died of PC (47.19%). Of the 350 randomly assigned patients, 88 (25.14%) received WPRT. In men younger than 65 years, WPRT was associated with a significantly lower ACM risk (adjusted hazard ratio [AHR], 0.33 [95% CI, 0.11 to 0.97]; P = .04) and lower PCSM risk (AHR, 0.17 [95% CI, 0.02 to 1.35]; P = .09) after adjusting for covariates, whereas this was not the case for men 65 years or older. CONCLUSION WPRT has the potential to reduce mortality in younger men with unfavorable-risk PC.