ESTRO 2022 - Abstract Book

S507

Abstract book

ESTRO 2022

Conclusion The significant changes in IPSS indicate a notable effect on patient-reported urinary toxicity in the first three months following MR-guided prostate cancer SBRT using a 1.5T MR-Linac. A clinically relevant increase in IPSS was observed in a large proportion of patients, thus leaving room for improvement. Currently, we are investigating the association between the accumulated dose to the bladder and bladder wall and patient-reported acute urinary toxicity. This approach is feasible due to the availability of high-quality 1.5T MR images and treatment plan data for each fraction.

PD-0578 Long term toxicity of prostate-only or pelvic SBRT: A Comparative Study

Withdrawn

PD-0579 Ultra-hypo compared to moderate-hypo fractionated prostate IGRT with HDR brachytherapy boost.

A. Martin 1 , D. Carignan 2 , M. Beaudry 1 , É. Ménard 3 , W. Foster 1 , É. Vigneault 1 , S. Magnan 1 , B. Lachance 1 , É. Poulin 1 , F. Lacroix 1 , L. Archambault 4 , L. Beaulieu 4 , P. Després 5 1 CHU de Québec - Université Laval, Radiation Oncology, Quebec, Canada; 2 CRCHU de Québec, CRCEO, Quebec, Canada; 3 CHRCHU de Québec , CRCEO, Quebec, Canada; 4 CRCHU de Québec - Université Laval, Physique médicale, Quebec, Canada; 5 CRCHU de Québec - Université Laval , Physique médicale, Quebec, Canada Purpose or Objective To compare treatment tolerability & toxicity of an HDR brachytherapy (BB) combined to an ultra-hypo fractionated (UHF) prostate radiation therapy regimen as opposed to two moderate hypo fractionated (MHF). Materials and Methods This interim analysis of a prospective mono centric phase 2 study includes 75 prostate cancer patients, mostly intermediate risk, recruited between July 2015 and September 2021. Using an image guided radiation therapy technique (IGRT), 25 Gy in 5 fractions plus 15 Gy HDR BB were delivered to the experimental arm (Exp). The control groups consisted of contemporary patients treated with IGRT and HDR BB (15 Gy HDR) with either 37.5 Gy in 15 fractions (Ctrl; n=225) or 36 Gy in 12 fractions (Ctrl-2; n=119). IGRT treatment time is reported. Patient reported outcomes were collected using the International Prostate Symptom Score (IPSS) questionnaire at baseline and at each follow-up visits. A comparative linear mixed model analysis was performed on log transformed IPSS values. Expanded prostate cancer index composite-26 (EPIC-26) was also reported and compared for the Exp and Ctrl population with a mixed model analysis. Biochemical relapse-free survival (BRFS) is reported. Results The 3 groups were similar with no statistical differences regarding: the median age (68 years), stage (T1C), Gleason scores (7), PSA (<10) and risk grouping (favorable intermediate). Median follow-up was 8, 63 and 49 months respectively for Exp, Ctrl & Ctrl-2. The mixed model analysis showed that mean IPSS scores diverge significantly, favoring the Exp compared to Ctrl for all time points except at 9 and 48 months. When comparing to Ctrl-2, there were significant differences in favor of Exp at 6, 12 and 24 months. Analysis of EPIC-26 data showed no differences throughout follow-up between Exp and Ctrl-2 in all domains. The median treatment time to deliver IGRT was 7 days in the UHF group compared to 17 and 22 days in the control groups. Considering a short follow-up in the Exp group, its BRFS was 100% compared to 94.6 and 88.5% for Ctrl-2 & Ctrl respectively, these differences are not significative.