ESTRO 2025 - Abstract Book

S1220

Clinical – Lower GI

ESTRO 2025

Our institutional online-ART workflow on-couch is explained in figure 2: 1st CBCT image adquisition, to asses daily anatomical changes, influencer contours modification (rectum, bowel and bladder) propagated by AI, next step evaluates target contours (CTVs, PTVs) for finally review two dosimetric plans ( Scheduled and Adapted). After clinical staff carries out plan selection, Quality Assurance assessment is mandatory. After the 2nd CBCT is reviewed, patient treatment can be administered.

Results: Online-ART workflow in rectal cancer patients, seems to be simple and quick, being able to adapt anatomical structures (influencers) with deformable image registration (DIR), just needing to edit in a few number of fractions in the rigid image registration (RIR) screen, to modify target volumes and adapt them to the new patient anatomic changes. Overall average treatment time (door-to-door) was 20min27seconds. The adapted plan was selected in 96% of fractions delivered. Conclusion: We can conclude that online-ART for rectal cancer patients is a feasible technique for locally-advanced rectal cancer treatments, significantly reducing doses to the OARs, compared to a clinically scheduled plan selection strategy, without compromising target coverage, and employing short periods of on-couch treatment time. Treatment was well tolerated in all the patients analyzed, and overall average treatment time was not increased comparing with IGRT conventional treatments.

Keywords: Online, ART, rectum

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Digital Poster Inflammatory Biomarkers and LIPI Score to Predict Treatment Response in Locally Advanced Rectal Cancer Treated with Total Neoadjuvant Therapy Zilan Başkan 1 , Ali Kaan Güren 2 , Hilal Alkış 1 , Tuğçe Bulun Akyol 3 , Mustafa Adlı 1 1 Department of Radiation Oncology, Marmara University School of Medicine, Istanbul, Turkey. 2 Department of Medical Oncology, Marmara University School of Medicine, Istanbul, Turkey. 3 Department of Internal Medicine, Marmara University School of Medicine, Istanbul, Turkey