Comparison of conventionally fractionated and hypofractionated schedule for post-prostatectomy salvage radiotherapy: Early results from non-randomized observational study.

Abstract

e551 Background: Data on hypofractionated radiotherapy in definitive treatment of prostate cancer are maturing; however, limited information is available for hypofractionated radiotherapy after prostatectomy. We aimed to compare hypofractionated and conventionally fractionated radiotherapy in salvage setting for biochemically recurrent prostate cancer. Methods: A retrospective analysis was performed in 106 patients with proven PSA recurrence treated to the prostate bed. Patients were non-randomly, in a alternating fashion, subjected to either 52.5 Gy in 20 fractions of 2.625 Gy over 4 weeks (N = 57, hypofractionated group) or 66 Gy in 33 fractions of 2 Gy over 6.5 weeks (N = 49, conventionally fractionated group). There was no statistically significant difference in pathologic T-stage and Gleason score distribution between the groups. In the conventionally fractionated group there were more patients with positive margins (p = 0.01), more prevalent concomitant hormonal therapy (50.9% vs 61.2%, p = 0.001), but less long-term hormonal therapy (21.4% vs 81%, p < 0.001), compared to hypofractionated group. Median follow-up was 20 months (range 6-36 months). Failure (PSA nadir+0.2) rates between the groups were compared using Cox proportional hazards model. Radiation-related side-effects were assessed using RTOG scoring scale. Results: At this early point, 13 patients (22.8%), and 6 patients (12.2%) experienced treatment failure in the hypofractionated group and conventionally fractionated group, respectively (HR 3.1, 95%CI (1.5-6.3)). More late grade 2 gastrointestinal and genitourinary side-effects were observed in conventionally fractionated group (4.1% vs 1.8%, and 2% vs 0%, p = 0.01, respectively). No grade 3 toxicities were observed. Conclusions: More initial biochemical failures were observed in hypofractionated group compared to conventionally fractionated group. However, baseline heterogeneity between the groups and short follow-up preclude any causal observation of differential efficacy between these two schedules. Randomized phase II trial is planned to prospectively compare these two regimens.