Deep Learning-Assisted Skeletal Muscle Radiation Attenuation at C3 Predicts Survival in Head and Neck Cancer

Head and neck cancer (HNC) patients face an increased risk of malnutrition due to lifestyle, tumor localization, and treatment effects. While skeletal muscle area (SMA) and radiation attenuation (SM-RA) at the third lumbar vertebra (L3) are established prognostic markers, L3 is not routinely available in head and neck imaging. The prognostic value of SM-RA at the third cervical vertebra (C3) remains unclear. This study assesses whether SMA and SM-RA at C3 predict locoregional control (LRC) and overall survival (OS) in HNC. We analyzed 904 HNC cases with head and neck CT scans. A deep learning pipeline identified C3, and SMA/SM-RA were quantified via automated segmentation with manual verification. Cox proportional hazards models assessed associations with LRC and OS, adjusting for clinical factors. Median SMA and SM-RA were 36.64 cm² (IQR: 30.12–42.44) and 50.77 HU (IQR: 43.04–57.39). In multivariate analysis, lower SMA (HR 1.62, 95% CI: 1.02–2.58, p = 0.04), lower SM-RA (HR 1.89, 95% CI: 1.30–2.79, p < 0.001), and advanced T stage (HR 1.50, 95% CI: 1.06–2.12, p = 0.02) were prognostic for LRC. OS predictors included advanced T stage (HR 2.17, 95% CI: 1.64–2.87, p < 0.001), age ≥70 years (HR 1.40, 95% CI: 1.00–1.96, p = 0.05), male sex (HR 1.64, 95% CI: 1.02–2.63, p = 0.04), and lower SM-RA (HR 2.15, 95% CI: 1.56–2.96, p < 0.001). Deep learning-assisted SM-RA assessment at C3 outperforms SMA for LRC and OS in HNC, supporting its use as a routine biomarker and L3 alternative.