Is radiotherapy after radical prostatectomy associated with higher other-cause mortality?

Purpose: The aim of this study was to reveal the association between the other-cause mortality (OCM) and post-radical prostatectomy (RP) salvage radiotherapy (sRT) in men with prostate cancer (PCa). Methods: A retrospective study was carried out with patients who had PCa and underwent RP ± sRT in a high-volume cancer center between 2005 and February 2019. Data from 1955 patients were subjected to a 1:1 matching for age, initial PSA, pathological (p)T/N stages, and ISUP score, which yielding 439 RP + RT (group 1) vs 439 RP-only cases (group 2), without any residual difference. Primary and secondary endpoints of the study were OCM and cancer-specific mortality (CSM). Kaplan–Meier, log-rank, and cox regression tests were used for purpose of the study. Results: The median follow-up time after RP was 5.3 years (interquartile range: 4.0–7.3). After matching, of all deaths that occurred during the study period, 16 in group 1 and 35 in group 2 were attributed to other causes (p = 0.006). 5-year OCM rate of patients who received sRT (1.2%) was significantly lower compared to patients that underwent RP-only (4.4%, p < 0.001). 19 versus 16 patients died of PCa, respectively (p = 0.61). There was no CSM risk difference between groups (p = 0.29). Older patients had an increased risk of OCM (hazard ratio [HR]:1.10 [95%CI 1.05–1.17], p < 0.001) and post-RP RT was associated with lower OCM (HR: 0.28 [95%CI 0.15–0.51], p < 0.001) in multivariable model. pT/N stages and ISUP score were strongly associated with CSM, but not with OCM. Conclusion: OCM was not higher in patients who had sRT with or without ADT. Excess OCM in favor of RP-only patients may be cautiously explained with higher-performance status/life expectancy of patients who selected for RT after RP in our cohort.