Difference in risk factors associated with biochemical recurrence after salvage RT compared to post-prostatectomy patients with negative margins.

Abstract

39 Background: Previous research has also shown that higher pathologic stage, higher Gleason score (GS) and positive margins are associated with increased rates of disease recurrence after prostatectomy and may be indicators for early intervention with adjuvant or salvage radiotherapy (SRT). Conversely, a negative surgical margin is a negative prognostic factor for the success of SRT. We sought to investigate the relative significance of prognostic factors in patients grouped by margin status and differences in their response to treatment. Methods: 227 patients were treated with SRT at our institution between Jan 2005 and Dec 2013. Patients with positive lymph nodes at surgery, those treated with adjuvant radiation and patients with metastases prior to SRT were excluded, leaving 196 for analysis. Biochemical recurrence (BCR) was defined as post-SRT PSA nadir + 0.2 ng/mL. Median follow-up was 48 mo. Covariates evaluated were factors found to be significant in previous studies on SRT (pre-SRT PSA, pathologic stage, GS) as well as treatment to the pelvis vs fossa. Patients were grouped by margins and evaluated using Kaplan-Meier and multivariate Cox regression. Results: In univariate analysis of patients with positive margins significant factors for increased rates of recurrence were pre-SRT PSA (p = 0.016), GS (p < 0.001), and pathologic stage (p < 0.001). Treatment to the pelvis was not significant. Conversely, in patients with negative margins, pre-SRT PSA and GS no longer significantly affected BCR and pathologic stage only approached significance (p = 0.061). In these patients treatment to the pelvis was significantly associated with decreased BCR (p = 0.005). On multivariate analysis these trends in significance were maintained. Conclusions: In post-prostatectomy patients with negative margins treatment to the pelvis is associated with improved bPFS, while traditional factors associated with recurrence such as pathologic stage, GS and pre-treatment PSA were not significant. Patients with negative margins and PSA recurrence after prostatectomy should be considered for treatment to the pelvic nodes, even in the absence of nodal involvement on imaging.