Development and validation of equations for predicting appendicular skeletal muscle mass in male patients with head and neck cancer and normal hydration status.

Objective: Muscle mass is typically assessed by abdominal computed tomography, magnetic resonance imaging, and dual-energy x-ray absorptiometry. However, these tests are not routinely performed in patients with head and neck cancer (HNC), making sarcopenia assessment difficult. The aim of this study was to develop and validate equations for predicting appendicular skeletal muscle mass (ASM) from data obtained in daily medical practice, with bioelectrical impedance analysis (BIA)-measured appendicular skeletal muscle mass (BIA-ASM) as a reference.
Methods: This cross-sectional study included 103 men with HNC who were randomly placed into development and validation groups. The prediction equations for BIA-ASM were developed by multiple regression analysis and validated by Bland-Altman analyses. The estimated skeletal muscle mass index (eSMI) was also statistically evaluated to discriminate the cutoff value for BIA-measured SMI according to the Asian Working Groups for Sarcopenia.
Results: Two practical equations, which included 24-h urinary creatinine excretion volume (24hUCrV), handgrip strength (HGS), body weight (BW), and body height (BHt), were developed: ASM (kg) = -39.46 + (3.557 × 24hUCrV [g]) + (0.08872 × HGS [kg]) + (0.1263 × BW [kg]) + (0.2661 × BHt [cm]) if available for 24hUCrV (adjusted R ²  = 0.8905), and ASM (kg) = -42.60 + (0.1643 × HGS [kg]) + (0.1589 × BW [kg]) + (0.2807 × BHt [cm]) if not (adjusted R ²  = 0.8589). ASM estimated by these two equations showed a significantly strong correlation with BIA-ASM (R > 0.900). Bland-Altman analyses showed a good agreement, and eSMI accuracy was high (>80%) in both equations.
Conclusions: These two equations are a valid option for estimating ASM and diagnosing sarcopenia in patients with HNC in all facilities without special equipment.
Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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