Multidimensional Longitudinal Assessment of Oral Mucositis Burden and Functional Impact in Head and Neck Cancer Patients Undergoing Radiotherapy or Chemoradiotherapy: A Retrospective and Exploratory Observational Study

Background/Objectives: Oral mucositis is a frequent and clinically significant acute toxicity in patients undergoing radiotherapy or chemoradiotherapy for head and neck cancer, with substantial consequences for swallowing function, nutritional status, and quality of life. Conventional clinician-reported toxicity grading may not fully capture the multidimensional burden experienced by patients. This study aimed to perform a longitudinal multidimensional assessment of treatment-related oral mucositis by evaluating the relationship between clinician-reported toxicity, objective mucosal injury, patient-reported swallowing-related quality of life, and nutritional status. Methods: In this retrospective observational study, 32 of 54 consecutively screened patients with locally advanced head and neck cancer treated with curative-intent radiotherapy, with or without concurrent chemotherapy, were included. Oral mucositis was assessed using the Common Terminology Criteria for Adverse Events (CTCAE) and the Oral Mucositis Assessment Scale (OMAS). Swallowing-related quality of life was evaluated using the MD Anderson Dysphagia Inventory (MDADI). Body weight was recorded longitudinally as an indicator of nutritional status. Correlations between OMAS scores and clinical outcome measures were analyzed at predefined timepoints using Spearman’s rank correlation coefficient. Results: All patients developed treatment-related oral mucositis, with peak severity occurring during the acute treatment phase. During the acute treatment phase, OMAS scores demonstrated a moderate positive correlation with clinician-reported toxicity (CTCAE) and inverse correlations with MDADI scores. A significant inverse association between OMAS and MDADI composite score persisted at treatment completion (ρ = −0.41, p = 0.022). Body weight progressively declined during treatment, although no statistically significant correlation with OMAS severity was observed. Conclusions: A multidimensional assessment integrating clinician-reported toxicity, objective mucosal evaluation, and patient-reported functional outcomes provides a broader characterization of oral mucositis burden in patients undergoing radiotherapy-based treatment for head and neck cancer. These findings support the potential value of integrated toxicity assessment strategies to improve supportive care monitoring in clinical practice.