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The aim of the study was to analyze the cohort of head and neck squamous cell carcinoma (HNSCC) patients (pts) who underwent radiotherapy (RT) or radiotherapy with concurrent chemotherapy (RT-CHT) and their body mass index (BMI) and skeletal muscle index (SMI) pattern of variation at 3 months after treatment completion. 

From 2016 to 2020, we enrolled 73 consecutive HNSCC pts treated by with exclusive or postoperative RT (14 pts) or RT-CHT (59 pts). Pts’ t₀ (at time of diagnosis) and t₃ (3 months after treatment completion) CT scans were retrieved to measure skeletal muscle as cross-section area (CSA) in a single slice at the level of C3 vertebra. Skeletal muscle area was defined as the pixel area between the radiodensity range of -29 and +150 Hounsfield Units (HU) and SMI calculated. Charlson Score was used to assess comorbidities, resulting in a median score of 4 (range: 2-11).

Pts were followed-up up to disease progression, relapse or death. Median follow-up was 16 months (range: 3 – 70 months), local-progression-free survival was analyzed. We further analyzed the BMI and SMI variance with variables coming from patients’ clinical data, Mann-Whitney test was used and p-value <0,05 was considered as significative.

20 events were recorded: 9 disease progressions and 11 tumor relapses. The 82% of pts was free of progression at 1 year (95% C.I. 0.70-0.89). We analyzed BMI and SMI at t₀ and t₃. At t₀, average BMI was 25.79 (SD 4.06), while, at t₃, it was 24.46 (SD 3.56) with a reduction in 54 pts (73,97%). The difference was evaluated by Wilcoxon signer-rank test, showing a BMI decrease of -1,33 (SD 1.81) and p-value <0.0001.

At t₀, average SMI was 57,14 (SD 11,01), while, at t₃, it was 59,17 (SD 11,84) with a reduction in 26 pts (35,62%). The difference was evaluated by Wilcoxon signed-rank test, showing a SMI increase of 2,03 (SD 5,47) and p-value <0.0055. BMI and SMI variance did not significantly correlate with analyzed clinical variables.  

The SMI increment found in our population could be justified by the nutritional interventions and supplementation monitored by seriate nutritional follow-up. Furthermore, our study suggests that the assessment of nutritional status by BMI could be potentially insufficient since BMI variations could hide muscle mass variations, impacting in HNSCC prognosis. SMI could represent a more reliable way in muscle mass analysis that could be easily integrated in radiation oncology setting.