Dose–Dependence Relationship Between Radiotherapy and Oral Mucositis in Patients With Head and Neck Cancer: A Retrospective Study

Introduction and Purpose To evaluate the association between radiotherapy (RT) exposure and the presence and severity of radiation‐induced oral mucositis (RIOM) in patients with head and neck cancer (HNC). Methods This retrospective observational study analyzed medical records of 121 patients with HNC treated with 3D conformal RT at a referral hospital in Brazil (2020–2023). Sociodemographic, clinical, and RT‐related variables were collected. RIOM was clinically assessed using World Health Organization (WHO) criteria and analyzed using three approaches: presence of RIOM, overall severity (grades 0–4), and severity among affected patients (grades 1–4). Analyses included descriptive, bivariate, and adjusted multivariable binary and ordinal logistic regression models. Results RIOM was identified in 51 patients (42.1%). No cases of WHO grade 4 were observed. In multivariable analysis, intraoral tumor (aOR = 9.06; 95% CI: 3.51–23.38; p < 0.001), number of RT sessions (aOR = 1.11 per session; 95% CI: 1.04–1.17; p < 0.001), cumulative dose (aOR = 1.05 per Gy; 95% CI: 1.02–1.08; p = 0.001) and female sex (aOR = 3.10; 95% CI: 1.13–8.43; p = 0.027) were independently associated with RIOM presence. Intraoral tumor and increasing RT exposure remained significantly associated with greater RIOM severity ( p < 0.01) in ordinal models. Preventive laser therapy showed a protective trend in bivariate analysis but did not remain significant after adjustment. Conclusion RT exposure and intraoral tumor location were the main factors associated with both the presence and severity of RIOM, highlighting the importance of anatomical site and radiation burden for risk stratification.