ESTRO 2025 - Abstract Book

S988

Clinical – Head & neck

ESTRO 2025

Trismus is a detrimental radiation-induced side-effect that significantly jeopardizes the patients quality of life. This interim analysis suggests a potential correlation between the dosimetry of the LPs’ muscles and the onset of radiation-induced trismus. Further analysis will be provided at completed accrual. Keywords: Trismus, Head&Neck, Radiotherapy References: 1) Spahiu O, Grossi C, Cavallin C, Chiofalo V, Cuffini EM, Lo Zito B, Catena F, Tortarolo A, Levis M, Piancino MG, Ricardi U, Iorio GC. Definitive radiotherapy and trismus in HNC patients: A critical review. Crit Rev Oncol Hematol. 2024 Nov;203:104486. doi: 10.1016/j.critrevonc.2024.104486. Epub 2024 Aug 27. PMID: 39197668.

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Digital Poster Cephalometric findings predict trismus in HNC patients: interim analysis of a prospective international study Cristiano Grossi 1 , Orges Spahiu 2 , Alessandro Tortarolo 3 , Elena Gallio 1 , Chiara Cavallin 1 , Valeria Chiofalo 1 , Erica Maria Cuffini 1 , Francesca Catena 1 , Chiara Casale 1 , Ada Celislami 1 , Mario Levis 1 , Maria Grazia Piancino 3 , Umberto Ricardi 1 , Giuseppe Carlo Iorio 1 1 Department of Oncology, Radiation Oncology, University of Turin, Turin, Italy. 2 Radiation Therapy Unit, University Hospital Center "Mother Teresa", Tirana, Italy. 3 Department of Surgical Sciences, Dental School, University of Turin, Turin, Italy Purpose/Objective: Trismus is a potential side effect for head and neck cancer (HNC) patients undergoing RT, defined as a maximum interincisal opening (MIO) ≤ 35 mm [1]. To date no consistent associations between baseline cephalometric/dental parameters and trismus incidence in nonmetastatic HNC patients treated with definitive RT (+/- chemotherapy) have been identified. This analysis aims to prospectively investigate potential cephalometric and dental trismus predictors. Material/Methods: Nonmetastatic HNC patients candidate to RT (either LINAC-based or Tomotherapy, +/- chemotherapy) were prospectively enrolled in an international study. Details on pre-existing conditions of the oral cavity, masticatory muscles, temporomandibular joint and structural craniofacial features were collected at baseline. MIO measurements to assess trismus were performed through the TheraBite use at baseline, RT-end, 1, 3-, 6-, 9-, and 12-months post-RT. Baseline dental status evaluations and skull teleradiographies were performed by orthodontist specialists. The correlation between these factors and changes in MIO (from pre-RT to the 6-months follow-up) was assessed using a linear regression model. Results: From November 2022 to August 2023, 38 patients were enrolled among two centers. 37 were eligible for the present analysis. Cephalometric tracings available for 28 patients showed that 64% had a mesodivergent cranial structure, 11% hypodivergent, and 25% hyperdivergent. Pre-RT dental screening led to preventative tooth extractions for 54% of patients, with a median of three teeth removed per patient. Following extraction, the median remaining teeth per patient was 18, with 22% fully edentulous and 59% having fewer than 20 teeth. Linear regression analysis showed that neither the number of teeth pre-RT nor intermaxillary divergence (SpP^GoGn, mean = 21.6° ± 6.1°) were correlated with MIO reduction (mean = -1.75 mm ± 4.3 mm) over time. However, a significant association (Fig.1) was found between increased mandibular posterior rotation (SpP^CoOr, mean = 1.6° ± 3.7°) and MIO reduction (p=0.01, regression coefficient = 0.64). No association was observed between