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

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).

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.

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.

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.