S1096
Clinical – Upper GI
ESTRO 2026
Digital Poster 3209
Progressive margin reduction in Pancreas SBRT on MR-Linac with target intrafraction tracking and gating using Comprehensive Motion Management (CMM) MICHELE RIGO 1 , CHIARA DE-COLLE 1 , ANDREA GAETANO ALLEGRA 1 , NICCOLO` GIAJ-LEVRA 1 , LUCA NICOSIA 1 , CAROLINA ORSATTI 1 , EDOARDO PASTORELLO 1 , FRANCESCO RICCHETTI 1 , ANDREA ROMEI 1 , NICOLA BIANCHI 1 , RICCARDO BORGESE 1 , ANTONIO DE SIMONE 1 , DAVIDE GURRERA 1 , STEFANIA NACCARATO 1 , GIANLUISA SICIGNANO 1 , ROBERTO PELLEGRINI 2 , RUGGERO RUGGIERI 1 , FILIPPO ALONGI 1,3 1 Advanced Radiation Oncology Department, IRCCS Sacro Cuore Don Calabria Hospital, Negrar di Valpolicella, Italy. 2 Medical Affair, Elekta AB, Stockholm, Sweden. 3 Radiation Oncology School, University of Brescia, Brescia, Italy Purpose/Objective: MR-guided stereotactic body radiotherapy (MRgSBRT) provides a breakthrough treatment option for patients with pancreatic cancer, where other radiotherapy treatment modalities often lack efficacy due to dose - limiting organs at risk (OARs), poor target visibility and reduced possibility to account for target motion. MR- Linac allows for improved treatment accuracy through better target and OARs visualization due to high soft tissue image quality and daily plan adaptation. Furthermore, newly clinically introduced CMM allows for target intrafraction tracking and gating without need of fiducials, enabling GTV-PTV margin reduction, OARs sparing and dose escalation. Here we report our experience of pancreas MRgSBRT with margin reduction using the CMM. Material/Methods: In September 2023 CMM was installed at our Institution and used for pancreas MRgSBRT. Schedules ranged from 5 to 10 fractions with total dose of 45 to 60 Gy. The following variables were reported: patients and treatment characteristics, beam-on time (treatment administration duration), beam-hold time (interruption due to gating) duty-cycle (total beam-on time on the entire delivery phase), positioning shifts. Results:
Between February 2024 and October 2025, 44 patients received pancreas SBRT on 1.5T MR-Linac using daily CMM, in free-breathing, without compression belt or abdominal mask. Mean age was 66 years. For online motion management we select GTV as “Anatomic Position Monitoring” structure and PTV as “Gating Envelope” and set the VOICE threshold at 95%. A 5 mm isotropic PTV margin was used for the first 16 patients and 1 mm for the last 28. All patients completed the planned treatment. The mean duty cycle for the 183 fractions was 91.35% (95%CI84.6-95.1%). Mean beam-
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