Sarcopenia is defined by the reduction in skeletal muscle mass and physical performance. It results in a decrease in muscle strength, overall physical activity, walking and the development of balance disorders and falls. It is one of the natural consequences of aging and contributes to frailty and the appearance of geriatric syndrome (s) (Chandapasirt et al, 2015; Cruz-Jentoft et al, 2010).

Its prevalence in patients with Head & Neck cancer is 39% (Hua et al, 2020) and is associated with an increase in postoperative complications (Achim et al, 2017; Bril et al, 2019), with greater toxicity of chemotherapy. (Wendrich et al, 2017) and reduced overall survival (Hua et al, 2020).

It is measured by CT scan (assessment of muscle volume with respect to L3 using IMAGE J software) (Teigen et al, 2018) and by clinical tests (performance tests) (Swartz et al, 2016, Cruz-Jentoft et al, 2010).

Several studies have shown a possible assessment of sarcopenia by measuring skeletal muscle mass with regard to C3 (Ufuk et al, 2019; Swartz et al, 2016).

This trial aims to evaluate the prevalence of sarcopenia in head and neck cancer evaluated by CT at C3.

Inclusion Criteria:

• patient over 18 years old,
• affiliated to the social security scheme,
• suffering from locally advanced head & neck cancer (stages I to IVB) at diagnosis,
• not operable,
• justifying treatment by radiotherapy, whether or not associated with chemotherapy or targeted therapy (eg: monoclonal antibodies, immunotherapy) whatever the proposed modalities.

Exclusion Criteria:

• patient treated by non-conservative surgery and cervical lymph node dissection making it impossible to assess muscle mass with regard to C3,
• metastatic disease,
• minor patient,
• adult patient under guardianship,
• pregnancy or breastfeeding in progress.

Adult patient diagnosed with head & neck carcinoma non operable and treated by radiotherapy and/or chemotherapy and/or targeted therapy.