AbstractBackgroundResponse rates of immune checkpoint inhibitor (ICI) therapy for recurrent and/or metastatic head and neck squamous cell carcinoma (R/M HNSCC) are low.Patients and MethodsThis retrospective multicentre cohort study evaluates the predictive and prognostic value of weight loss and changes in body composition prior and during therapy. Patient, tumor, and treatment characteristics of 98 patients were retrieved, including neutrophil and platelet‐lymphocyte‐ratio (NLR and PLR). Programmed death‐ligand 1 (PD‐L1) expression was determined on residual material. Cachexia was defined according to Fearon et al. (2011). Skeletal muscle (SM), visceral adipose tissue (VAT), and subcutaneous adipose tissue (SAT) were evaluated on computed tomography scans at the third lumbar vertebrae level. Univariable and multivariable regression analyses were performed for 6 months progression free survival (PFS6m) and overall survival (OS).ResultsSignificant early weight loss (>2%) during the first 6 weeks of therapy was shown in 34 patients (35%). This patient subgroup had a significantly higher NLR and PLR at baseline. NLR and PLR were inversely correlated with SM and VAT index. Independent predictors of PFS6m were lower World Health Organization performance status (HR 0.16 [0.04–0.54] p = 0.003), higher baseline SAT index (HR 1.045 [1.02–1.08] p = 0.003), and weight loss <2% (HR 0.85 [0.74–0.98] p = 0.03). Baseline cachexia in combination with >2% early weight loss remained a predictor of OS, independent of PD‐L1 expression (HR 2.09 [1.11–3.92] p = 0.02, HR 2.18 [1.13–4.21] p = 0.02).ConclusionWe conclude that the combination of cachexia at baseline and weight loss during ICI therapy is associated with worse OS in R/M HNSCC patients, independent of PD‐L1 expression.