151751-Najiba-Chargi

201 Systemic therapy: skeletal muscle mass and chemoradiotherapy simulation was performed in all patients. All patients were treated with intensity-modulated radiotherapy (IMRT) or volumetric modulate arc therapy (VMAT). The radiation treatment con - sisted of 46 Gy of elective irradiation to both sides of the neck (level II-IV in case of node-neg - ative neck and level II-V in case of cervical lymph node metastases), followed by a boost of 24 Gy in 12 fractions to the primary tumor and the involved nodes in case of node-positive disease, to a total dose 70 Gy. IMAGE EVALUATION Measurement of SMM was performed at the level of C3 according to a method previously described by Swartz et al. 18 In brief, a single axial CT-slide at level C3 was selected using a standard procedure: the first slide to completely show the entire vertebral arc when scroll- ing through the C3 vertebra from caudal to cephalic direction was selected. Skeletal muscle tissue was identified using Hounsfield unit (HU) ranges settings from -29 to +150 HU, to avoid overestimation of skeletal muscle area and to exclude fatty tissue (which has a HU value below -30). 19 The outer contours of the sternocleidomastoid and paravertebral muscles were traced manually (figure 1) using the Worldmatch Research Software Package, an in-house software package designed for image evaluation, registration and delineation for radiotherapy. The cross-sectional muscle area (CSMA) at the level of C3 was calculated as the sum of the de - lineated areas of the paravertebral muscles and both sternocleidomastoid muscles within HU ranges of -29 to +150 in cm 2 . All CT slides were analyzed by a single researcher (S.B.). The CSMA at the level of C3 was then normalized for stature to calculate a cervical skeletal muscle index (CSMI). 20 Figure 1. Skeletal muscle area segmentation at the level of C3. STATISTICAL ANALYSIS All analyses were performed using SPSS version 23.0 (SPSS Inc. Chicago IL, USA). Continuous data are represented as mean ± standard deviation (SD). Categorical data are represented as the number and percentage of total. The optimum SMM cut-off value based on CDLT was ob - tained using the optimal point in a receiver optimum stratification for binary outcomes (in this 11