ESTRO 2022 - Abstract Book

S1193

Abstract book

ESTRO 2022

Materials and Methods We evaluated the effect of WPRT and retroperitoneal RT on hematological toxicity in patients treated for pN1 PCa in the PART trial (NCT03079323), a prospective phase 2 single-arm trial, and searched for predictive dose-volume effects for BM. Blood counts were depicted in time evolution of delta levels, and time to recovery with respect to baseline. HemT was graded according to the CTCAE v4.0. BM was delineated as lumbosacral spine (LSS), iliac crests (IC), lower pelvis (LP), whole pelvis (WP), retroperitoneal (RP) and combined WP+RP (ALL), and the relative dose-volume histograms were calculated. Results The first 50 patients of the PART study were included in this trial. HemT was very acceptable, with no G3 or higher toxicity except for absolute lymphocyte count (ALC). Acute and late G3 ALC was present in 49% and 16% of the patients, respectively. More than 50% of the patients had full hematological recovery at the last time of follow-up, except for white blood cell count (WBC) and lymphocytes. BM volume LSS V50 Gy was significantly correlated with late % lymphocytes decline, and IC V50 Gy was correlated with both acute and late decline of ALC. None of the dose on the BM volumes was significantly associated with the time to recovery. Conclusion This is the first trial reporting on HemT and dose-volume effects for BM caused by extended-field radiotherapy in chemo- naive patients. General toxicity appeared to be low, except for decline in ALC. L. Nicosia 1 , C. Vitale 2 , F. Cuccia 2 , V. Figlia 2 , N. Giaj-Levra 2 , R. Mazzola 2 , F. Ricchetti 2 , M. Rigo 2 , R. Ruggero 2 , S. Cavalleri 3 , F. Alongi 2 1 Advanced Radiation Oncology Department, IRCCS Sacro Cuore Don Calabria Hospital, Negrar, Italy; 2 IRCCS Sacro Cuore Don Calabria Hospital, Advanced Radiation Oncology Department, Negrar, Italy; 3 IRCCS Sacro Cuore Don Calabria Hospital, Urology Division, Negrar, Italy Purpose or Objective conventionally fractionated postoperative radiotherapy demonstrated to reduce biochemical relapse in prostate adenocarcinoma (PCa), and early-salvage RT (esRT) demonstrated similar oncological results as compared with adjuvant RT (aRT), but with a safer toxicity profile. Given the PCa low α / β ratio would be of interest to evaluate the role of hypofractionation also in the postoperative setting. Materials and Methods the mono-institutional data of 304 PCa patients were retrospectively analyzed. 105 patients underwent aRT, 77 esRT, and 122 salvage RT (sRT). Mild-hypofractionated treatment dose in 30 fractions were 66 Gy in the aRT group, and 67.5 Gy in the salvage group. End-point of the study was the progression-free survival (PFS), biochemical relapse-free survival (BRFS), overall survival (OS) and toxicity. Results the median follow-up was 33 months. The 3-year PFS and BRFS was 85.2% and 82%, respectively. The factors associated with a worst PFS at the univariate analysis (UVA) were: high Gleason score, pT ≥ 3, esRT, concomitant hormone therapy (HT), and pelvic RT. In particular, aRT and sRT reported a significantly higher 3-year PFS compared to esRT at the UVA (93%, 85.4%, and 74.1%; p=0.000). Nevertheless, at the multivariate analysis (MVA) only Gleason score, pT and concomitant HT remains significantly correlated with PFS. Treatment of the relapse was: HT in 43% cases, stereotactic body radiotherapy (SBRT) in 43% patients, and HT+SBRT in 14% patients. At the last follow-up 8 patients deceased since, only two of which by PCa progression. Grade 1-2 GU toxicity during RT was: urgency (36%), dysuria (23%), increased urinary frequency (12.1%), and urinary retention (11.8%). Nevertheless, the majority of symptoms were present at the baseline. Grade 3 severe toxicity was represented by 10 (3.2%) cases of incontinence and 3 (1%) cases of urgency. The incidence of any-grade RT-related GU toxicity was significantly higher in the aRT group than the salvage group (esRT + sRT) (83.8% versus 64.5%). When comparing the incidence of any-grade RT-related GU toxicity in the aRT, esRT, and sRT groups we observed a significant correlation favoring sRT, over esRT, and aRT. Conclusion mild-hypofractionated RT seems to be safe and to provide local control rates similar to conventionally fractionated regimens at three-year follow-up. Hypofractionated early-salvage radiotherapy reported similar results as the adjuvant regimen, and confirms its safer toxicity profile. No unexpected severe toxicity was reported, the majority of which were already present at the baseline. PO-1407 Postoperative hypofractionated RT: toxicity and efficacy in a series of 304 prostate adenocarcinoma

PO-1408 Two-fraction prostate SABR vs. two-fraction HDR brachytherapy: does dose heterogeneity matter?

R. Correa 1 , G. Morton 1 , H. Chung 1 , C. Tseng 1 , P. Cheung 1 , W. Chu 1 , S. Liu 1 , M. McGuffin 1 , A. Shahid 1 , M. Davidson 1 , A. Ravi 2 , J. Helou 3 , Y. Alayed 4 , L. Zhang 1 , A. Mamedov 1 , A. Loblaw 1