Outcomes of salvage radiotherapy for recurrent prostate cancer after radical prostatectomy.

Introduction: Salvage radiotherapy (SRT) provides effective biochemical control for patients with prostate cancer who have prostate-specific antigen (PSA) failure after radical prostatectomy. However, the effect of SRT on long-term clinical outcomes remains unknown. Therefore, we report the natural history of patients treated with SRT. Methods: We identified 84 Chinese patients with prostate cancer treated with SRT to the prostatic fossa alone during 2006-2017 at Tuen Mun Hospital, Hong Kong. Survival was calculated using Kaplan-Meier method. Log rank test and Cox regression were used to determine significance of clinical parameters with outcomes. Results: Median SRT dose given was 70 Gy (range, 64-76 Gy). Median pre-SRT PSA level was 0.4 ng/mL (0.2-7.4 ng/mL). After SRT, 47 (56%) patients had undetectable (< 0.1 ng/mL) PSA levels. After median follow-up of 48 months (2 months to 10 years), 25 (30%) patients had further biochemical progression. Subsequently, 12 patients received androgen deprivation therapy and nine (11%) developed distant metastasis. The 5-year biochemical progression-free survival, androgen deprivation therapy-free survival and metastasis-free survival were 62.7%, 83.5% and 86.7%, respectively. Early PSA failure after radical prostatectomy (hazard ratio=7.4), negative surgical margin (hazard ratio=2.7), positive extracapsular extension (hazard ratio=4.6), and detectable PSA levels after SRT (hazard ratio=17.3) were associated with lower biochemical progression-free survival after SRT. Conclusions: High-dose SRT with intensity-modulated radiotherapy/volumetric modulated arc radiotherapy is an effective local treatment that can prevent distant metastasis and avoid the need for androgen deprivation therapy in Chinese patients who have PSA failure after radical prostatectomy.