Age-stratified clinical interpretation of AWGS2025 sarcopenia criteria in head and neck cancer treated with definitive chemoradiotherapy: Comparison with AWGS2019

OBJECTIVE: The AWGS2025 update extends sarcopenia diagnosis to adults aged 50-64 years, requires concurrent low muscle mass and low muscle strength, and introduces BMI-stratified muscle mass thresholds. We aimed to examine how these changes alter case identification in patients with head and neck cancer (HNC) undergoing definitive chemoradiotherapy (CRT). METHODS: We retrospectively analyzed 97 consecutive patients with HNC who underwent pretreatment assessment before definitive CRT. AWGS2025 was applied to patients aged ≥ 50 years, and AWGS2019 and AWGS2025 were cross-classified in those aged ≥ 65 years. We compared agreement, treatment selection, cisplatin completion, and selected acute toxicities in age-stratified analyses. RESULTS: Among patients aged ≥ 65 years (n = 55), sarcopenia prevalence was 23.6% by AWGS2019 and 20.0% by AWGS2025, with substantial agreement (κ = 0.79). In older adults, discordance was driven mainly by removal of physical performance from the diagnostic algorithm. Among triCDDP-treated older adults, the clearest acute-toxicity signal in sarcopenic patients was grade ≥ 3 radiation dermatitis. AWGS2025 additionally classified 6/35 (17.1%) patients aged 50-64 years as sarcopenic. In this small subgroup, treatment intensity and selected acute toxicities were not clearly increased. CONCLUSION: In HNC treated with definitive CRT, AWGS2025 represents an age-stratified diagnostic reclassification rather than a replacement for AWGS2019. In older adults, an AWGS2025 diagnosis may identify patients at increased risk of selected acute toxicities, particularly severe radiation dermatitis, whereas its clinical meaning in middle-aged adults remains exploratory.