ESTRO 2025 - Abstract Book

S3180

Physics - Inter-fraction motion management and offline adaptive radiotherapy

ESTRO 2025

References: Teoh S, Ooms A, George B, Owens R, Chu KY, Drabble J, Robinson M, Parkes MJ, Swan L, Griffiths L, Nugent K. Evaluation of hypofractionated adaptive radiotherapy using the MR Linac in localised pancreatic cancer: protocol summary of the Emerald-Pancreas phase 1/expansion study located at Oxford University Hospital, UK. BMJ open. 2023 Sep 1;13(9):e068906.

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Digital Poster Evaluation of delivered dose and correlation with toxicities for radiotherapy of head and neck cancers Eustache Gnacadja 1,2 , Sara Poeta 1 , Tatiana Dragan 3 , Nick Reynaert 1 , Younes Jourani 1 1 Department of Medical Physics, Université Libre de Bruxelles (ULB), Hôpital Universitaire de Bruxelles (H.U.B), Institut Jules Bordet, Brussels, Belgium. 2 MAS-PT-ID, Ion Beam Applications, Louvain-la-Neuve, Belgium. 3 Department of Radiation Oncology, Université Libre de Bruxelles (ULB), Hôpital Universitaire de Bruxelles (H.U.B), Institut Jules Bordet, Brussels, Belgium Purpose/Objective: Dysphagia and xerostomia are two of the most reported side effects in head and neck (H&N) radiotherapy. The objectives of this study are, on one hand, to correlate these side effects with selected dosimetric parameters for a cohort of patients belonging to an ongoing institutional prospective trial (1), and on the other hand, to estimate the delivered dose distribution for a selection of patients, to quantify the discrepancies between planned and delivered doses. Material/Methods: For the 46 patients included in the study, statistical analyses were conducted to determine which OARs were correlated with a dysphagia score higher than 45, and then 70, on the MD Anderson Dysphagia Inventory (MDADI) scale. The global xerostomia score reported by patients, and the Common Terminology Criteria for Adverse Events (CTCAE) scores collected by the physician were subjected to the same statistical analyses. For 5 of the 46 patients in the cohort, the delivered dose was estimated, based on deformable image registration between the planning CT and each daily CBCT. For each patient, the mean doses received by OARs related to dysphagia and xerostomia were recalculated for each session and accumulated over the entire treatment course. Accumulated and planned doses were compared. Results: Univariate statistical analyses showed that planned mean doses to the superior pharyngeal constrictor muscle, oral cavity and contra-lateral parotid gland were correlated with the MDADI score, while the mean doses to the cervical esophagus, contra-lateral submandibular gland, and sublingual gland were correlated with the xerostomia global score. Regarding CTCAE scores, no statistically significant conclusions could be observed. Multivariate analyses highlighted the middle pharyngeal constrictor muscle and soft palate as predictors of dysphagia on the MDADI scale, while the global xerostomia score was well predicted by a model including the sublingual and the contra-lateral parotid glands. Among the 5 patients for whom a dose recalculation and accumulation methodology was implemented, the 3 patients who did not receive adaptive treatment showed acceptable discrepancies (ranging from 0.01 to 3.7 Gy) between accumulated and planned mean doses. For the 2 patients who underwent adaptive treatment, larger discrepancies, up to 6 Gy for certain OARs, were observed. Conclusion: Correlation studies between toxicities and dosimetric parameters are crucial to identify the key OARs whose sparing limits dysphagia and xerostomia for H&N cancer patients treated with radiotherapy. The discrepancies observed between planned and delivered doses highlight the importance of implementing a dose evaluation technique throughout treatment for these patients.