Radiotherapy after radical prostatectomy for prostate cancer: clinical outcomes and factors influencing biochemical recurrence.

Abstract

Radiotherapy (RT) after radical prostatectomy (RP) includes adjuvant radiotherapy (ART) and salvage radiotherapy (SRT), which can prevent or cure biochemical recurrence. To evaluate long-term outcomes of RT after RP and to examine factors affecting biochemical recurrence-free survival (bRFS). Sixty-six received ART and 73 received SRT between 2005 and 2012 were included. The clinical outcomes and late toxicities were evaluated. Univariate and multivariate analyses were performed to examine factors affecting bRFS. Median follow-up from RP was 111months. Five-year bRFS and 10-year distant metastasis-free survival from RP were 82.8% and 84.5% in ART, and 74.6% and 92.4% in SRT, respectively. The most frequent late toxicity was hematuria, which was higher in ART (p = .01). No recurrence within RT field was occurred. On univariate analysis, pelvic RT was associated with favorable bRFS in ART (p = .048). In SRT, post-RP prostate-specific antigen (PSA) level (< 0.05ng/mL), PSA nadir after RT (≤ 0.01ng/mL), and time to PSA nadir (≥ 10months) were associated with favorable bRFS (p = .03, p < .001, and p = .002, respectively). On multivariate analysis, post-RP PSA level and time to PSA nadir were independent predictive factors for bRFS in SRT (p = .04 and p = .005). ART and SRT had favorable outcomes with no recurrence within RT field. In SRT, the time to PSA nadir after RT (≥ 10months) was found to be a new predictor for favorable bRFS and useful in assessing treatment efficacy.