Cut-off values for low skeletal muscle mass at the level of the third cervical vertebra (C3) in patients with head and neck cancer

Background: Low skeletal muscle mass is associated with adverse outcomes in patients with cancer. For patients with head and neck cancer (HNC), skeletal muscle mass is often assessed at the third cervical vertebra on head and neck imaging. Due to the unavailability of standardized cut-off values for low skeletal muscle mass in patients with head and cancer, there is heterogeneousness of cut-off values for low skeletal muscle mass described in literature. Therefore, we aim to provide standardized cut-off values for low skeletal muscle mass in HNC patients. Methods: A retrospective cohort study was performed. Between 2008 and 2018, HNC patients with head and neck imaging were included. Skeletal muscle area (SMA) was manually delineated at the level of the third cervical vertebra and corrected for patients squared height to obtain the cervical skeletal muscle mass index. Gender and body-mass index specific cut-off values for low skeletal muscle mass were calculated based on mean cervical skeletal muscle mass index minus 2 standard deviations as suggested in literature. Results: Of the 1,415 included patients, the majority was male (69.8%) and had a body mass index below 25 kg/m2 (59.2%). A primary tumor localization in the oropharynx (35.3%) and a tumor, node, metastasis stage IV tumor (60.5%) were most frequently observed. Cervical skeletal muscle mass index was significantly correlated with gender (r(2)=0.4, P<0.01) and body mass index (r(2)=0.4, P<0.01). For male patients with a body mass index <25 and >= 25 kg/m(2), a cervical skeletal muscle mass index of respectively <= 6.8 and <= 8.5 cm(2)/m(2) was defined for low skeletal muscle mass. For female patients with a body mass index <25 and >= 25 kg/m(2), a cervical skeletal muscle mass index of respectively <= 5.3 and <= 6.4 cm(2)/m(2) was defined for low skeletal muscle mass. Conclusions: This study is the first to provide standardized cut-off values for low skeletal muscle mass at the level of the third cervical vertebra in patients with HNC. This information may aid in the uniformity of low skeletal muscle mass definition in research.