Radiation Therapy After Radical Prostatectomy is Associated With Higher Other-Cause Mortality

Abstract PURPOSE:To test the association between external beam radiotherapy (EBRT) after radical prostatectomy (RP) vs RP only on rates of other-cause mortality (OCM) in men with prostate cancer (PCa).PATIENTS AND METHODS:Within the 2004-2016 Surveillance, Epidemiology and End Results database, we identified 181,849 localized PCa patients, of whom 168,041 received RP only vs 13,808 who received RP+EBRT. Cumulative incidence plots displayed OCM between RP vs RP+EBRT after propensity score matching for age, PSA, clinical T and N stages, and biopsy Gleason scores. Multivariable competing risks regression models addressed OCM, after adjustment for cancer-specific mortality (CSM). Stratifications were made according to low- vs intermediate- vs high-risk groups and additionally according to age groups of ≤60, 61-70 and ≥71 years, within each risk group.RESULTS:In low-, intermediate- and high-risk patients, RP+EBRT rates were 2.7, 5.4 and 17.0% respectively. After matching, ten-year OCM rates between RP and RP+EBRT were 7.7 vs 16.2% in low-, 9.4 vs 13.6% in intermediate- and 11.4 vs 13.5% in high-risk patients (all p<0.001), which respectively resulted in multivariable HR of 2.1, 1.3 and 1.2 (all p<0.001). In subgroup analyses, excess OCM was recorded in low-risk RP+EBRT patients of all age groups (all p≤0.03), but only in the older age group in intermediate-risk patients (61-70 years, p=0.03) and finally, only in the oldest age group in high-risk patients (≥71 years, p=0.02).CONCLUSIONS:Excess OCM was recorded in patients exposed to RT after RP. Its extent was most pronounced in low-risk patients, decreased in intermediate-risk patients and was lowest in high-risk patients.