ESTRO 2024 - Abstract Book

S2513

Clinical - Urology

ESTRO 2024

year outcomes of the HYPO-RT-PC randomised, non-inferiority, phase 3 trial. Lancet. 2019 Aug 3;394(10196):385 395. doi: 10.1016/S0140-6736(19)31131-6. Epub 2019 Jun 18. PMID: 31227373.

2) Brand DH, Tree AC, Ostler P, van der Voet H, Loblaw A, Chu W, Ford D, Tolan S, Jain S, Martin A, Staffurth J, Camilleri P, Kancherla K, Frew J, Chan A, Dayes IS, Henderson D, Brown S, Cruickshank C, Burnett S, Duffton A, Griffin C, Hinder V, Morrison K, Naismith O, Hall E, van As N; PACE Trial Investigators. Intensity-modulated fractionated radiotherapy versus stereotactic body radiotherapy for prostate cancer (PACE-B): acute toxicity findings from an international, randomised, open-label, phase 3, non-inferiority trial. Lancet Oncol. 2019 Nov;20(11):1531-1543. doi: 10.1016/S1470-2045(19)30569-8. Epub 2019 Sep 17. PMID: 31540791; PMCID: PMC6838670.

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Phase II Study of MR-guided Prostate Stereotactic Body Radiotherapy in Seven Days: Toxicity Analysis

Jens Van Loon, Jacques Bodenstein Bezuidenhout, Benedikt Engels, Guy Soete, Tim Everaert, Anne-Sophie Bom, Benjamin Vanspeybroeck, Nele Platteaux, Sven Van Laere, Thierry Gevaert, Mark De Ridder

UZ Brussel, VUB, Radiotherapy, Brussels, Belgium

Purpose/Objective:

Ultra-hypofractionated stereotactic body radiotherapy (SBRT) is gaining prominence as the primary therapeutic approach for clinically localized prostate cancer due to its low α/β -ratio. Here we present the toxicity profile of a prospective trial, called Proseven, where we administer 36 Gy (5 x 7.2Gy) to the PTV prescribed on the 90% isodose line, 40Gy (5 x 8Gy) to the CTV and a simultaneous integrated boost on the gross tumor volume (GTV) up to a total dose of 42Gy (5 x 8.4Gy), within an overall treatment time (OTT) of seven calendar days. The primary aim of this study was to evaluate the safety of dose-escalation on the GTV using MRI-guided radiotherapy on the MRIdian system (Viewray Inc).

Material/Methods:

This phase II Study of MR-guided prostate SBRT in seven days was approved by the Ethics committee of UZ Brussels (EC-2021-192 and NCT04896801). A sample size of 120 was required to detect an increase of 10% in grade 2+ (grade 2 or higher) genitourinary (GU) and gastro-intestinal (GI) toxicity, compared to the PACE B trial (grade 2+ toxicity for GU and GI were respectively 30.8% and 15.7% according to Common Terminology Criteria for Adverse Events (CTCAE v4.03)) (1). We report intermediate toxicities found in the first 98 enrolled patients. Toxicity was scored using CTCAE guidelines, based on an intention-to-treat analysis. Proseven trial recruitment and follow-up are still ongoing.

Results: