151751-Najiba-Chargi

113 Surgery: skeletal muscle mass, systemic inflammation and flap reconstruction INTRODUCTION Microvascular tissue transfer is the gold standard for reconstruction of complex head and neck defects after extensive resections for head and neck cancer (HNC) or osteoradionecrosis, or traumas. Reconstructive flap surgery can lead to improved function and aesthetics but is time-consum- ing and associated with significant postoperative morbidity. Survival rate of flaps depends on various factors, among which are age, comorbidities and many unknown factors. 1–3 Ongoing research is required to identify key predictors for postoperative morbidity, to enable better pre-operative risk-analysis for development of more individualized treatment planning aiming at improving treatment outcomes. Several studies have demonstrated that poor nutritional status and body composition changes are associated with an increased risk of surgical complications. 4,5 HNC patients often present with inadequate oral intake due to tumor site and treatment-related side effects (e.g., xerosto - mia, mucositis). This may lead to a decrease of lean body mass of which skeletal muscle mass (SMM) is the largest contributor. The prevalence of low SMM, also referred to as sarcopenia, in patients with HNC is estimated to be approximately 40%. 6 Loss of SMM in patients with cancer is often accompanied with a gain in fat mass, which leads to ‘’hidden sarcopenia’’. 7 Body mass index (BMI) is therefore a poor representative of patient’s body composition. It is already known that surgically treated patients with elevated BMI tend to have longer operative times and endure more blood loss. 8,9 However, sometimes elevated BMI may have a protective effect also known as the obesity paradox. 10 Hidden sarcopenia might explain why BMI has shown to have no predictive value for surgical complications in HNC patients who undergo reconstructive surgery. 11,12 Low SMM has shown to predict surgical complications as well as dose-limiting toxicities and decreased survival. 6,13–16 SMM can be quantified on routinely performed diagnostic imaging using computed tomography (CT) or magnetic resonance imaging (MRI) at the level of the third lumbar vertebrae (L3) or the third cervical vertebrae (C3). 17–19 For head and neck patients, imaging at the level of C3 is routinely performed in the diagnostic workup and for treatment evaluation. Recently, we performed a study in HNC patients undergoing reconstruction by use of free fibular flap (FFF) and found low SMM to be predictive for complications and prognostic for survival. 20 This finding is reinforced by a recently performed study in 168 HNC patients who underwent free flap reconstruction in which low SMM was a predictor for complications. 21 Another recent study in HNC patients undergoing free flap reconstruction showed that low SMM was associated with discharge to post-acute care facilities (instead of home) indicating that patients with low SMM are less tolerant to reconstructive surgery. 22 These studies only in- cluded patients who had preoperative abdominal CT scans for SMMmeasurement at the level of the third lumbar vertebrae (L3). Although SMMmeasurements at the level of L3 is common in oncological research 23 , this may lead to an inclusion bias in HNC patients because only 7