Dysphagia as a primary predictor of malnutrition in head and neck cancer: Psychometric validation and diagnostic accuracy of the Greek MDADI

Objectives To assess the synergistic impact of radiotherapy-induced xerostomia and dysphagia on malnutrition in Greek Head and Neck Cancer (HNC) survivors compared with matched controls, and to psychometrically validate the Greek version of the MD Anderson Dysphagia Inventory (MDADI). Materials and methods A cross-sectional, case-control study was conducted with 66 HNC patients (3 months post-RT) and 67 age- and sex-matched healthy controls (Oct 2024–Apr 2025). The study adhered to STROBE guidelines (Ethics No. 37871). Participants completed the MDADI, Xerostomia Inventory (XI), and PG-SGA Short Form. Statistical analyses included Cronbach's alpha for validation, Mann–Whitney U tests, Spearman's ρ, multivariable logistic regression, and Receiver Operating Characteristic (ROC) curve analysis to determine diagnostic accuracy. Results The Greek MDADI demonstrated excellent internal consistency (α = 0.92) and discriminant validity (Patients: 61.0 vs. Controls: 83.0, p < 0.001). Xerostomia and dysphagia were highly prevalent and strongly correlated (ρ = −0.69, p < 0.001). In the multivariable model, dysphagia emerged as the sole independent predictor of malnutrition (OR = 0.86, 95% CI: 0.77–0.95, p = 0.004), indicating a 14% risk reduction for every 1-point improvement in MDADI. ROC analysis identified an MDADI score of <53 as the optimal cutoff for detecting malnutrition risk (AUC = 0.78, Sensitivity 55%, Specificity 93%). Conclusions Dysphagia is the primary driver of malnutrition in the early post-RT period. The Greek MDADI is a valid clinical tool, and a score below 53 should serve as a "red flag" triggering immediate nutritional and speech-pathology intervention. Integrated management of the xerostomia-dysphagia-malnutrition cluster is essential for survivorship care.