Impact of Body Mass Index on Treatment Outcomes in Locally Advanced Head and Neck Cancer Patients Treated With Definitive Chemoradiotherapy or Radiotherapy Alone

ABSTRACT Background Body Mass Index (BMI) is a readily measured indicator of nutritional status; however, its impact on outcomes in head and neck cancer (HNC) patients remains understudied. This study evaluated the impact of pre‐treatment BMI on toxicities and survival in such patients. Methods This retrospective study included 212 patients of locally advanced HNC treated with definitive concurrent chemoradiotherapy or radiotherapy alone. Patients were categorized into BMI < 25 kg/m 2 and ≥ 25 kg/m 2 . Toxicities were assessed using CTCAE v5.0. Overall survival (OS) and locoregional control (LRC) were analyzed using the Kaplan–Meier method. Results Eighty‐six percent of patients had BMI of < 25Kg/m 2 . These patients experienced significantly higher rates of grade ≥ 2 mucositis, dermatitis, candidiasis, and greater need for nutritional support (44.7%; p = 0.039). Median OS and LRC were 25 and 24 months, respectively. Three‐year OS and LRC were 46.3% and 39%. BMI category, T stage, and nodal stage independently predicted OS. Conclusion BMI < 25 Kg/m 2 patients treated with definitive chemoradiotherapy or radiotherapy alone are more prone to treatment‐related toxicities and have inferior survival outcomes. Early nutritional assessment and intervention should be integrated into routine management to improve treatment outcomes.