Functional and oncological outcomes of salvage external beam radiotherapy following robot-assisted radical prostatectomy in a Canadian cohort

Introduction: We sought to determine the impact of salvage radiotherapy (SRT) on oncological and functional outcomes of patients with prostate cancer after biochemical recurrence (BCR) following robot-assisted radical prostatectomy (RARP).Methods: Data of 70 patients with prostate cancer treated with SRT after developing BCR were retrospectively analyzed from a prospectively collected RARP database of 740 men. Oncological (prostate- specific antigen [PSA]) and functional (pads/day, International Prostate Symptom Score [IPSS], and Sexual Health Inventory for Men [SHIM]) outcomes were reported at six, 12, and 24 months after RT and adjusted for pre-SRT status.Results: Men who underwent SRT had a mean age, PSA, and time from radical prostatectomy (RP) to RT of 61.8 years (60.1‒63.6), 0.5 ng/ml (0.2‒0.8), and 458 days (307‒747), respectively. Freedom from biochemical failure (FFBF) post-SRT, defined as a PSA nadir <0.2 ng/mL, was observed in 89%, 93%, and 81%, at six, 12, and 24 months, respectively. Undetectable PSA was observed in 14%, 35%, and 40% at the same time points, respectively. There was no significant difference in urinary continence post-SRT (p=0.56). Rate of strict continence (0 pads/day) was 71% at 24 months compared to 78% pre-SRT. Mean IPSS at six, 12, and 24 months was 3.4, 3.6, and 3.6, respectively compared to pre-RT score of 3.3 (p=0.61). The mean SHIM score pre-SRT was comparable at all time points following treatment (p=0.86).Conclusions: In this unique Canadian experience, it appears that early SRT is highly effective for the treatment of BCR following RARP with little impact on urinary continence and potency outcomes.