151751-Najiba-Chargi

114 CHAPTER 7 advanced-stage HNC patients are likely to undergo abdominal imaging as part of screening for distant metastasis with PET-CT. 24 Another marker receiving increased attention across various cancer types is an elevated neu- trophil-to-lymphocyte ratio (NLR), a biomarker for systemic inflammation. An elevated NLR has shown to be prognostic for decreased survival in a variety of cancers such as breast cancer, 25 colorectal cancer, 26 esophageal cancer, 27 and pancreatic cancer 28 . Elevated NLR is also pre - dictive for surgical complications in patients with cancer. 29,30 NLR can be easily quantified by dividing routinely measured neutrophil count by lymphocyte count. This study aims to investigate the impact of pre-operative low SMM and elevated systemic inflammation (elevated NLR-ratio) on postoperative complications, length of hospital stays, and disease-free survival (DFS) and overall survival (OS) in patients undergoing head and neck microvascular free flap reconstruction. MATERIAL AND METHODS PATIENTS AND STUDY DESIGN In a retrospective study, all patients who underwent flap reconstructive surgery at the de- partment of Oral and Maxillofacial Surgery of Queen Elizabeth hospital in Birmingham, United Kingdom, between January 2007 and January 2020, were included. All clinical and demograph - ic variables were collected by use of electronic medical records. SKELETAL MUSCLE MASS SMM was measured as skeletal muscle area (SMA) on pre-treatment imaging of the head and neck at the level of the third cervical vertebrae (C3). The axial slide which showed both trans - verse processes and the entire vertebral arc was selected for segmentation of muscle tissue. On CT, muscle area was defined as the pixel area between the muscle-specific radiodensity range of -29 and +150 Hounsfield Units (HU). SMA was calculated as the sum of the delineated areas of the paravertebral muscles and both sternocleidomastoideus muscles. Segmentation of muscle tissue was manually performed using the commercially available software package SliceOmatic (Tomovision, Canada) by a single researcher (N.C). An example of segmentation at the level of C3 is shown in supplemental figure 1. SMA at the level of C3 was converted to SMA at the level of L3 using a previously published formula as shown in formula 1. 17 The lumbar skeletal muscle index (LSMI) was calculated by correcting SMM at the level of L3 for squared height as shown in formula 2. Low SMM was defined as a LSMI below 43.2 cm 2 /m 2 , this cutoff value was determined in a separate cohort of HNC patients. 13