Salvage Radiotherapy versus Observation for Biochemical Recurrence following Radical Prostatectomy for Prostate Cancer: A Matched Pair Analysis

SIMPLE SUMMARY: Salvage radiotherapy improves oncologic outcomes in prostate cancer patients who develop biochemical recurrence after radical prostatectomy. However, the evidence on hard clinical endpoints is scarce. Within this study, we compare the long-term oncologic outcomes of patients with biochemical recurrence after prostatectomy, who were treated with either salvage radiotherapy or no radiotherapy. Our results show that patients who were treated with salvage radiotherapy after the development of biochemical recurrence following radical prostatectomy had a lower risk of developing metastasis and lower risk of death within the follow-up. These findings further underline the curative potential of salvage radiotherapy in the case of biochemical recurrence after radical prostatectomy, and should be discussed with these patients. ABSTRACT: Background: Salvage radiotherapy (SRT) improves oncologic outcomes in prostate cancer (PCa) patients who develop biochemical recurrence (BCR) after radical prostatectomy (RP). However, evidence on hard clinical endpoints is scarce. We compare long-term oncologic outcomes of SRT versus no radiotherapy (noRT) in patients with BCR after RP. Patients and methods: Within a multi-institutional database, we identified patients with BCR after RP between 1989 and 2016 for PCa. Patients with lymph node invasion, with adjuvant radiotherapy, or with additional androgen deprivation therapy at BCR were excluded. In all patients with SRT, SRT was delivered to the prostatic bed only. Propensity score matching (PSM) was performed to account for differences in pathologic tumor characteristics. Kaplan–Meier analyses and Cox regression models tested the effect of SRT versus no RT on metastasis-free (MFS) and overall survival (OS). Results: Of 1832 patients with BCR, 32.9% (n = 603) received SRT without ADT. The median follow-up was 95.9 months. Median total SRT dose was 70.2 Gy. After 1:1 PSM, at 15 years after RP, MFS and OS rates were 84.3 versus 76.9% (p < 0.001) and 85.3 versus 74.4% (p = 0.04) for SRT and noRT, respectively. In multivariable Cox regression models, SRT was an independent predictor for metastasis (HR: 0.37, p < 0.001) and OS (HR: 0.64, p = 0.03). Conclusion: This is the first matched-pair analysis investigating the impact of SRT versus observation only in post-RP recurrent PCa. After compensating for established risk factors, SRT was associated with better long-term MFS and OS. These results on clinical endpoints underline the curative potential of SRT.