Epidermoid carcinoma (SCC) is the predominant histology of cancers of the oral cavity, pharynx, and larynx. In Brazil, 11,200 new cases of oral cavity cancer are estimated in men and 3,500 in women for each year of the 2018-2019 biennium. The disease causes high mortality and morbidity, affecting swallowing and dysphagia, leading to weight loss and cachexia. Cancer cachexia is marked by involuntary muscle loss leading to progressive functional impairment and can not be reversed by traditional nutritional support. Recent publications show that muscle mass can predict certain outcomes such as survival. Methods for assessing body composition have been developed and validated for research, and the area of a skeletal muscle, which can be measured by cross-sectional images, is a valid marker of total body mass. The CT evaluation of the region of the third and fourth lumbar vertebra (L3-L4) are accurate and accepted as a method for evaluating body composition. However, given the locoregional nature of the dissemination of this SCC, usually the L3-L4 level is not available on CT, and this is a limitation for the use of CT to assess cachexia in these patients. This study will be divided into three steps. In the first step, 20 patients with cross-sectional CT images of patients with head and neck cancer diagnosis will be selected to verify the intra-class variation at different evaluation times. The second step aims to evaluate the correlation of the muscular area obtained through the L3 region with the area of the neck muscles. The third step will evaluate the prognostic role of the neck muscle area of HNSCC patients. The area of the neck muscle of the first CT scan obtained prior to the beginning of treatment will be evaluated and the ratio of this area with the survival rate will be calculated.