Moderately hypofractionated salvage radiotherapy in patients with biochemical recurrence of prostate cancer after prostatectomy: long-term results and comparative analysis of two schedules

 Fabio Matrone, Alessandra Donofrio, Giuseppe Fanetti, Alberto Revelant, Jerry Polesel, Paola Chiovati, Roberto Bortolus

Abstract:

Hypofractionation in salvage radiotherapy (HSRT) for biochemical recurrence of prostatic cancer after prostatectomy is a debated issue and at present, it should be considered purely investigational because of the lack of evidence supporting its use. In this study, we report the outcomes of patients presenting with biochemical recurrence after radical prostatectomy who received HSRT. The additional aim of this study is to compare two moderately HSRT schedules. Patients treated to prostate bed with daily Image Guided-VMAT and a total dose of 65 Gy/26 fractions (Group A) or 66 Gy/30 fractions (Group B) were included in the study. Inclusion criteria were: pN0/pNx, pre-HSRT PSA ≥0.2 ng/ml and ≤1 ng/ml, no evidence of pelvic/extrapelvic disease at restaging, no pelvic irradiation or dose boost on macroscopic local recurrence, no neoadjuvant/concomitant Androgen Deprivation Therapy (ADT), follow-up ≥36 months, and available pre/post HSRT data. Genitourinary (GU) and gastrointestinal (GI) toxicities, early and late, were assessed using CTCAE Vers. 5.0. One hundred patients were retrospectively identified to 50 in each group. Median follow-up was 59 months. All patients completed the prescribed HSRT. 5-year biochemical failure-free survival, local control, distant relapse-free survival, and ADT- free survival were 52.1%, 85.9%, 63.7%, and 73.2%, respectively. No significant differences in these outcomes were found between the two groups. On multivariate analysis, a hypofractionation schedule was not associated with any outcome, but ISUP score ≥ 4 and pre-HSRT PSA were associated with worse biochemical failure-free survival while only ISUP score ≥ 4 was associated with worse distant relapse-free survival. No Grade 3 GU/GI acute event was reported; 6 (6%) and 2 (2%) patients experienced late Grade ≥ 2 GU and GI events, respectively. No difference was found between the two groups neither in acute nor in late GU/GI toxicities. Our findings demonstrate that HSRT is feasible, effective, and safe. Our analysis did not show any significant difference between the two hypofractionated schedules. Further studies and randomized controlled trials are required in order to confirm these results and to identify the optimal hypofractionated schedule in the salvage setting.