Prognostic Nutritional Index as a Predictor of Treatment-Related Toxicity in Head and Neck Cancer Patients Undergoing Chemoradiotherapy.

Background The Prognostic Nutritional Index (PNI) is a straightforward marker that reflects nutritional and inflammatory status, derived from serum albumin and lymphocyte count. The significance of predicting treatment-related toxicity in patients with head and neck cancer (HNC) receiving radiotherapy in conjunction with chemotherapy continues to hold clinical importance. This study aimed to assess the predictive capability of baseline PNI regarding severe acute and late radiation-induced toxicities (mucositis, dysphagia, xerostomia, weight loss)in HNC patients undergoing radiotherapy with either induction or concurrent chemotherapy. Methodology This retrospective cohort study comprised 150 patients with HNC who received treatment at a tertiary center from January 2021 to December 2025. The PNI was determined utilizing Onodera's formula, and patients were classified into low (<49.0) and high (≥49.0) PNI categories. The outcomes evaluated comprised severe acute toxicity (Common Terminology Criteria for Adverse Events, version 4.0 grade ≥3), weight loss exceeding 10% during treatment, and late toxicities (grade ≥2). Analyses using multivariable logistic and Cox regression were conducted. Results The median PNI was recorded at 49.0, with 50% of participants classified as having low PNI. Severe acute toxicity was observed in 64% of patients, whereas 20% experienced notable weight loss. Patients with low PNI experienced greater weight loss (32% compared to 8%) and a heightened risk after adjustment (odds ratio = 4.12). A low PNI was similarly linked to the occurrence of late mucositis (hazard ratio = 1.82). Conclusions A low baseline PNI serves as a predictor for treatment-related toxicity and may assist in identifying high-risk HNC patients who would benefit from early nutritional intervention.