151751-Najiba-Chargi

405 The elderly head and neck cancer patient: skeletal muscle mass and frailty Muscle function: muscle strength Overall muscle strength is strongly related with isometric handgrip strength (HGS). 17 HGS was measured using a Jamar hydraulic handheld dynamometer according to the recommendations of the American society of hand therapist’s (ASHT) and expressed in kilograms (kg). Patients were asked to squeeze maximally with each hand. The average score of the left and right hands was used for analysis. Patients had low HGS if the mean HGS was below 27kg (men) or below 16kg (women). 13 Skeletal muscle mass SMM was measured as cross-sectional muscle area (CSMA) on pretreatment CT or MRI imag - ing of the head-and-neck area at the level of the third cervical vertebrae (C3). The axial slide of the imaging which showed both transverse processes and the entire vertebral arc was selected for the segmentation of muscle tissue. For CT imaging, muscle area was defined as the pixel area between the radio density range of −29 and +150 Hounsfield units (HU), which is specific for muscle tissue. 18 For MRI, muscle area was manually segmented, and fatty tissue was manually excluded (Figure 1). Figure 1. Example of segmentation of skeletal muscle tissue at the level of the third cervical vertebra (C3) Two identical axial contrast enhanced computed tomography (CT) slides at the level of C3; left shows the muscle tissue unsegmented, right shows both sternocleidomastoid and paravertebral muscles segmented in red. Segmentation of muscle tissue was manually performed using the commercially available software package SliceOmatic (version 5.0, Tomovision, Canada) by a single researcher (C.M.) who was blinded for outcome regarding frailty and sarcopenia. Cross-sectional muscle area at the level of C3 was converted to CSMA at the level of L3 using a previously published formula. 19 The lumbar skeletal muscle index (SMI) was calculated by correcting SMM at the level of L3 for height. Patients had a low SMI if this value was ≤43.2 cm 2 /m 2 ; this cut-off value was established in a separate cohort of patients with head-and-neck cancer. 14 20