151751-Najiba-Chargi

70 CHAPTER 4 only adjust for coronal head tilt. Using our center’s patient positioning protocol, we expected very little to no sagittal tilt in our imaging. We corrected the observed MCSA by dividing by squared body height to determine a masseter muscle mass index (MSMI). The masseter muscle characteristics are dependent on various factors such as dental status and craniofacial structure. 22,27 MCSAwas adjusted by body height, as it has been established that muscle mass corrected by body height is an accurate adjust- ment method for other CSA measurements. 28 Although we found a significant difference in skeletal muscle mass and body composition indicators for groups based on MSMI, we only found a near significant difference in overall survival between patients classified as normal or lowMSMI (p=0.069). Conversely, in multivariate analysis lowMSI classification significantly predicted all-cause mortality. Another limitation of our retrospective design is that patient frailty and sarcopenia as de- fined by the European Working Group on Sarcopenia in Older People (EWGSOP) could not be assessed. Sarcopenia is diagnosed by evaluating muscle mass and muscle function. 6 Further prospective studies are needed that correlate masseter findings with muscle strength (e.g., by grip strength) and physical performance (e.g., by the Short Physical Performance Battery and the Timed Up and Go-test). Finally, whole-body PET-CT-scans are only performed in patients with advanced disease (stage III and IV). We expected that this would not cause any significant bias in our study as Swartz et al. found no significant difference in C3 or L3 CSA between patients with traumatic injury and head and neck cancer allowing for extrapolation to both healthy patients and patients with malignant disease. CONCLUSION We conclude that several masseter muscle parameters, namely MV, masseter CSA and MT, are significantly correlated (varying from moderate to strong) with cross-sectional muscle area at cervical and lumbar level. Additionally, MSMI, defined as masseter CSA divided by squared patient’s height in meters, proved to be a significant prognostic factor for decreased overall survival (HR 3.03). In patients without cross-sectional imaging at the level L3 or C3 or with impaired C3 measurements, masseter muscle parameters could serve as an alternative for assessment of skeletal muscle mass. We recommend further studies to determine factors in - fluencing masseter parameters as to formulate an improved method to correct for individual patient factors, e.g., dental status, previous dental disease, previous cancer treatment and facial morphologic features. Subsequently, this research should correlate masseter parame - ters with muscle strength and physical performance.