ESTRO 2022 - Abstract Book

S1206

Abstract book

ESTRO 2022

F. Matrone 1 , G. Fanetti 1 , A. Revelant 1 , J. Polesel 2 , P. Chiovati 3 , G. Franchin 1 , R. Bortolus 1

1 Centro di Riferimento Oncologico di Aviano (CRO) IRCCS, Division of Radiation Oncology, Aviano, Italy; 2 Centro di Riferimento Oncologico di Aviano (CRO) IRCCS, Unit of Cancer Epidemiology, Aviano, Italy; 3 Centro di Riferimento Oncologico di Aviano (CRO) IRCCS, Division of Medical Physics, Aviano, Italy Purpose or Objective Hypofractionation in salvage radiotherapy (SRT) for biochemical recurrence (BCR) of prostatic cancer after prostatectomy is a debated issue. We report the outcomes of 2 moderately hypofractionated schedules in pts who received SRT to prostate bed for BCR. Materials and Methods Pts treated with Image Guided-VMAT and a total dose of 65 Gy/26 fractions (Group A; BED=173.4 Gy for α / β =1.5) or 66 Gy/30 (Group B; BED=162.8 Gy for α / β =1.5) were considered. Inclusion criteria were: pN0/pNx, PSA at BCR ≥ 0.2 ng/ml and ≤ 1 ng/ml, no evidence of pelvic/extrapelvic disease at restaging (when indicated), no pelvic irradiation or boost on macroscopic local recurrence, follow-up ≥ 2 years and available pre/post SRT data. Concomitant ADT was used prevalently in pts with high risk features. Early and late toxicities were assessed using CTCAE Vers. 4.0. Results 150 pts were identified (Tab 1). Median follow-up was 67 months (IQR: 52-81) in group A and 38 (IQR: 30-46) in Group B (p<0.001). 3-year recurrence rate of biochemical, local and distant failure in Group A and Group B were 30.6% and 32.2% (p=0.928), 4.2% and 6.1% (p=0.562), 23.5% and 25.9% (p=0.961), respectively (Fig 1). Among pts with a distant failure pattern of relapse, 23 pts (82.1%) in Group A and 15 (71.4%) in Group B had oligometastatic relapse (p=0.494); 5 pts (17.9%) in Group A and 6 (28.6%) in Group B had polimetastatic relapse. 5 pts in Group A (2 oligoprogressive pts) and 4 pts in Group B (1 oligoprogressive pt) developed mCRPC; median hormone-sensitive time was 57 months in Group A and 14 in Group B. 3-year OS was 100% in group A and 92.2% pts in Group B (p=0.158), disease specific OS was 100% in Group A and 96.1% in Group B (p=0.319). On multivariate analysis, ISUP score ≥ 4 was associated with worse biochemical failure (HR=2.29, 95% CI: 1.25-4.23; p=0.008); ISUP score ≥ 4 (HR=2.08, 95% CI: 1.05-4.10, p=0.036) and time to BCR<24 months (HR=2.24, 95% CI: 1.09-4.62, p=0.028) were significantly associated with worse distant failure. Among pts undergoing concomitant ADT, pts in Group A reported a lower rate of biochemical (HR=0.19; 95% CI: 0.07-0.52) and distant failure (HR=0.17; 95% CI: 0.06- 0.49) than Group B (Fig 1). A significantly higher late genitourinary toxicity rate was observed in Group A (p=0.032).