S555
Clinical – Head & neck
ESTRO 2026
27.71 (SD=23.39). Nearly half of the patients reported functional impairment (MDADI physical<60: 46.99%; FACT-H&N HNCS<24: 50.60%). MIO significantly predicted EORTC OM difficulty (p<0.001), explaining 36.6% of variance. Each 1 mm decrease in MIO corresponded to 1.067-point increase in symptom score (Table 1A). Thresholds of MIO associated with functional impairment were identified as 36/41mm with predicted probability <0.5 respectively. Figure 1 shows trends in MIO and PROs over time post-RT.As exploratory analysis, quantitative MIO was further divided into 4 severity categories (Normal:>40mm (55.15%); mild:31-40mm (36.36%); moderate:21-30mm (7.88%); severe: ≤ 20mm (0.61%)) for cross-tabulation with agreement metrics with 4 levels of EORTC OM results. Only slight agreement was found (Kappa value=0.188, p-value<0.001).By defining MIO<35mm and EORTC OM level ≥ 3 as mouth-opening impairment (2-3), we identified patients with mismatched objective and PRO scores into 4 discordance groups. Sociodemographic variables of age, sex, year-post-RT were found significant predictors in multinomial logistic regressions. Parameter estimates are shown in Table 1B. In residual analysis, 5 predictor variables (age, sex, year-post-RT, educational level and employment status) explained 12.2% of residual variance (R ² =0.122, p-value<0.001). Older age and female were associated with lower residuals.
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Integrating objective and subjective measures of trismus in post-radiotherapy nasopharyngeal carcinoma patients: Comparison and concordance analysis Si Wing Tsui 1,2 , James C. H. Chow 1 , Jiang Zhang 2 , Karus P. S. Yeung 3 , Haylie P. Y. Wong 1 , Winkie W. K. Chong 1 , Tiffany K .K. Tse 3 , Alex K. C. Leung 1 , Ka Man Cheung 1 , Kwok Hung Au 1 , Benny C. Y. Zee 4 , Wai Tong Ng 5 , Wing Cheung Vincent Wu 2 , Jing Cai 2 1 Department of Clinical Oncology, Queen Elizabeth Hospital, Hong Kong, Hong Kong. 2 Department of Health Technology and Informatics, The Hong Kong Polytechnic University, Hong Kong, Hong Kong. 3 Department of Occupational Therapy, Queen Elizabeth Hospital, Hong Kong, Hong Kong. 4 Centre for Clinical Research and Biostatistics, Jockey Club School of Public Health and Primary Care, The Chinese University of Hong Kong, Hong Kong, Hong Kong. 5 Department of Clinical Oncology, School of Clinical Medicine, The University of Hong Kong, Hong Kong, Hong Kong Purpose/Objective: Trismus (reduced mouth-opening) is long-term complication following radiotherapy (RT) in nasopharyngeal carcinoma (NPC) patients. Clinicians frequently underestimate severity and frequency of treatment-related adverse effects compared to patient self-reports (1).This study aimed to compare objective measurement of trismus with patient-reported outcomes (PROs) related to oral and swallowing function in NPC, explore concordance and quantify extent to which objective measure explains variation in subjective outcomes, for optimizing patient-centred care. Material/Methods: This cross-sectional study included 166 disease-free NPC patients ( ≥ 3 years post-RT, 66-74Gy, treated between 2008-2020). Objective measurement of post- RT trismus was assessed using OraStrech maximum interincisal opening (MIO), while PROs were collected via validated instruments within 3 months: EORTC QLQ-H&N35 (Head and neck cancer-specific symptoms), MDADI physical subscale (swallowing distress), and FACT-H&N questionnaires (eating, speaking, discomfort). Primary analysis examined relationship between MIO and EORTC Opening Mouth (OM) Symptom Subscales using univariable linear regression. Secondary analyses included correlation tests, agreement metrics, discordance classification, and residual analysis for other PROs. IBM SPSS was used for statistical analysis. Results: Mean MIO was 41.07 mm (SD=7.98) at average of 7.89 years post-RT (SD=3.03). Mean EORTC OM score was
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