Early salvage versus adjuvant post-prostatectomy radiation therapy: Long-term results of a large institutional experience.

Abstract

99 Background: Randomized trials and consensus statements support consideration of adjuvant radiation therapy (ART) after radical prostatectomy (RP) for adverse pathologic features (pT3, positive margins), although its use remains low. Whether early salvage radiation therapy (ESRT) is as effective as ART remains unknown. The objective of this study was to compare outcomes after ART and ESRT. Methods: We performed a retrospective institutional analysis of 719 consecutive patients receiving post-RP RT from 1992 to 2013. ESRT was defined as RT for biochemical failure (BF) with post-RP PSA ≤ 0.5 ng/ml. All included ART and ESRT patients had adverse surgical pathologic features. Outcomes examined were freedom from BF (FFBF; rising PSA ≥ 0.2 ng/ml with subsequent confirmation), freedom from subsequent androgen deprivation therapy (FFADT), freedom from distant metastases (FFDM), and overall survival (OS). ART and ESRT were compared using multivariable analyses (MVA) with propensity score (PS) matching for pre-RP PSA, age at RT, Gleason score, pT-stage, and margin status. Results: 537 patients received salvage RT, of whom 195 received ESRT; 181 patients received ART. Median follow-up from RP was 7.0 and 8.1 years in the ART and ESRT cohorts, respectively. Median time to BF after RT was 4.4 and 4.7 years in the ART and ESRT cohorts, respectively. On MVA, ART was associated with improved 10-year FFBF (74 vs 60%, HR 0.36 [95% CI: 0.23-0.58], P < 0.0001) and 10-yr FFADT (91 vs 83%, HR 0.37 [95% CI: 0.18-0.76], P = 0.007). There were no significant differences in FFDM (96 vs 92%, HR 0.58 [95% CI: 0.19-1.7], P = 0.3), and OS (98 vs 95%, HR 1.24 [95% CI: 0.4-3.89], P = 0.7). After PS matching, ART (n = 169) remained significantly associated with improved FFBF (p < 0.0001) and FFADT (p = 0.01), compared to ESRT (n = 176). Conclusions: Post-prostatectomy RT confers excellent long-term prostate cancer control, a finding supported by the long follow-up in this series. ART is associated with improved FFBF and FFADT compared to ESRT, although there were no statistically significant differences in FFDM and OS. Optimal timing of postoperative RT further awaits the results of ongoing randomized trials.