ESTRO 2024 - Abstract Book

S2571

Clinical - Urology

ESTRO 2024

2820

Digital Poster

First clinical application of Comprehensive Motion Management on prostate SBRT using 1.5T MR-linac

Michele Rigo 1 , Niccolò Giaj-Levra 1 , Rosario Mazzola 1 , Luca Nicosia 1 , Francesco Ricchetti 1 , Edoardo Pastorello 1 , Andrea Gaetano Allegra 1 , Lorenzo Granello 1 , Antonio De Simone 1 , Davide Gurrera 1 , Stefania Naccarato 1 , Gianluisa Sicignano 1 , Riccardo Borgese 1 , Roberto G. Pellegrini 2 , Ruggero Ruggieri 1 , Filippo Alongi 3 1 IRCCS Sacro Cuore Don Calabria Hospital, Advanced Radiation Oncology Department, Negrar di Valpolicella, Italy. 2 Elekta AB, Medical Affairs, Stockholm, Sweden. 3 University of Brescia, Radiation Oncology School, Brescia, Italy

Purpose/Objective:

High-field MR-linac allows improved soft-tissue visualization of the tumour and the surroundings tissues. Furthermore, daily MR-imaging allows on-table adapted planning and real-time intra-fraction imaging without additional exposure to radiation. The recent implementation of Comprehensive Motion Management (CMM) guarantees more precise radiation treatments by interrupting the delivery when the target moves outside the defined position and enables radiation oncologist to perform target drift corrections. We report our first clinical experience on prostate adaptive SBRT with true tracking and automatic gating with high-field MR-Linac.

Material/Methods:

Between 26th September and 13rd October 2023, we treated 5 male patients affected by low-to-favourable intermediate prostate cancer. For treatment simulation we used a T2-weighted MR sequence that lasts 2 minutes. On this sequence we contour the target and the organs-at-risk. The GTV-to-PTV margins were 5 mm in all directions and 3 mm posteriorly. A 16-fields IMRT plan was prepared and daily adapted with adapt-to-shape workflow during every fraction. The 5-fraction delivered total dose was 35 Gy in low risk and 36.25 Gy in intermediate risk. The motion management was set to deliver the treatment when 100% of the GTV was contained within the PTV. We collected details and times of all treatment phases.

Results:

The median on-table time was 34 minutes. The daily 3D T2-weighted sequence acquisition lasted 2 minutes, the registration between daily sequence and reference sequence lasted 1 minute, the daily target and OARs contour definition lasted 4 to 5 minutes and the daily plan adaptation lasted between 7 and 9 minutes. The median delivery time was 17 minutes (range 15-20 minutes) with a median beam-on time of 14 minutes (range 13.5-17 minutes) and a median gating efficiency of 85% (range 82%-91%). Among the 25 delivered fractions only one drift corrections was needed and the baseline shift replanning lasted 1 minute. The patients performed all the sessions without any clinical issue.