Background: Reduced muscle mass has been associated with increased treatment complications in several tumor types. We evaluated the impact of skeletal muscle index (SMI) on prognosis and immune-related adverse events (IrAEs) in a cohort of recurrent/metastatic (R/M) head and neck squamous cell carcinoma (HNSCC) treated with immune checkpoints inhibitors (ICI).Methods: A single-institutional, retrospective study was performed including 61 consecutive patients of R/M HNSCC diagnosed between July 2015 and December 2018. SMI was quantified using a CT scan at L3 to evaluate body composition. Median baseline SMI was used to dichotomize patients in low and high SMI. Kaplan-Meier estimations were used to detect overall survival (OS) and progression-free survival (PFS). Toxicity was recorded using Common Terminology Criteria for Adverse Event v4.3.Results: Patients were 52 men (85.2%) with mean of age 57.7 years (SD 9.62), mainly oral cavity (n = 21; 34.4%). Low SMI was an independent factor for OS in the univariate (HR, 2.06; 95% CI, 1.14–3.73, p = 0.017) and multivariate Cox analyses (HR, 2.99; 95% CI, 1.29–6.94; p = 0.011). PFS was also reduced in patients with low SMI (PFS HR, 1.84; 95% CI, 1.08–3.12; p = 0.025). IrAEs occurred in 29 (47.5%) patients. There was no association between low SMI and IrAEs at any grade (OR, 0.56; 95% CI, 0.20–1.54; p = 0.261). However, grades 3 to 4 IrAEs were developed in seven patients of whom three had low SMI.Conclusions: Low SMI before ICI treatment in R/M HNSCC patients had a negative impact on OS and PFS. Further prospective research is needed to confirm the role of body composition as a predictive biomarker in ICI treatment.

Background: Growth Differentiation Factor 15 (GDF15) has emerged as a key biomarker and therapeutic target in oncology, with roles extending beyond cancer cachexia. Elevated GDF15 levels correlate with poor prognosis across several solid tumors, including colorectal, gastric, pancreatic, breast, lung, prostate, and head and neck cancers. GDF15 modulates tumor progression through PI3K/AKT, MAPK/ERK, and SMAD2/3 signaling, thereby promoting epithelial-to-mesenchymal transition, metastasis, immune evasion, and chemoresistance via Nrf2 stabilization and oxidative stress regulation. Methods: We performed a narrative review of the literature focusing on the role of GDF15 in solid tumors, with a particular emphasis on head and neck cancers. Results: In head and neck squamous cell carcinoma (HNSCC), GDF15 overexpression is linked to aggressive phenotypes, radioresistance, poor response to induction chemotherapy, and failure of immune checkpoint inhibitors (ICIs). Similar associations are observed in colorectal, pancreatic, and prostate cancer, where GDF15 contributes to metastasis and therapy resistance. Targeting the GDF15-GFRAL axis appears therapeutically promising: the monoclonal antibody ponsegromab improved cachexia-related outcomes in the PROACC-1 trial, while visugromab combined with nivolumab enhanced immune response in ICI-refractory tumors. Conclusions: Further investigation is warranted to delineate the role of GDF15 across malignancies, refine patient selection, and evaluate combinatorial approaches with existing treatments.