ESTRO 2024 - Abstract Book

S2238

Clinical - Upper GI

ESTRO 2024

2206

Digital Poster

First pilot worldwide adaptive treatment with Comprehensive Motion Management with 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:

1.5T MR-linac improves target volume and adjacent OARs visualization, ensuring high precision in radiation treatment delivery. Daily MR-imaging allows on-table adapted planning and real-time intra-fraction imaging without additional exposure to radiation. We aim to report the first pilot worldwide adaptive treatment with true tracking and automatic gating by means of high-field MR-Linac. This implementation allows to compensate for any respiratory and/or accidental movements of the target during RT delivery.

Material/Methods:

On 25th September 2023, we treated a 60-year-old female affected by liver oligometastasis from high grade serous ovarian carcinoma. For treatment simulation we used a 3D T2-navigated MR sequence in full exhale. On this sequence we contoured the target and the organs-at-risk. The PTV from GTV were 5 mm in all directions except 10 mm caudally. A 12-fields IMRT plan was prepared and daily adapted with adapt-to-shape workflow during every fraction. The treatment dose was 50 Gy in 5 daily fractions. The treatment was delivered in free-breathing modality.

Comprehensive Motion Management (CMM) was set to deliver the treatment when at least 95% of the GTV overlapped with the PTV. We collected details and times of all treatment phases.

Results:

The median on-table time was 36 minutes. The median daily 3D T2-navigated sequence acquisition lasted 10 minutes, the registration between daily sequence and reference sequence lasted 2 minutes, the daily target and OARs contour definition lasted 1 to 3 minutes, since no target shape correction was provided. The daily plan adaptation lasted between 5 and 7 minutes. The median delivery time was 15 minutes with a median beam-on time of 6 minutes (range 5-8 minutes) and a median gating efficiency of 33% (30-38%). No drift corrections were needed. The patient performed all the sessions without any clinical problems.

Conclusion: