151751-Najiba-Chargi

276 CHAPTER 15 used as an objective measurement tool for decision making and it may offer the opportunity for timely therapeutic intervention to potentially reverse muscle wasting. Therefore, this study will evaluate the patterns and predictors of changes in SMM in LA-HNC pa - tients treated with cisplatin-based CRT. In addition, this study will determine if low SMMbefore CRT or loss of SMM after CRT have a prognostic impact on OS and DFS in LA-HNC patients. MATERIAL & METHODS ETHICAL APPROVAL The design of this study was approved by the Medical Ethical Research Committee of the University Medical Center Utrecht, METC ID: 17-365/C. The requirement for informed consent from patients was waived because of its retrospective design. STUDY DESIGN A retrospective cohort study was conducted. All patients diagnosed with LA-HNC and treated with cisplatin-based CRT in primary or postoperative setting between 2012 and 2018 in our tertiary referral center were screened for inclusion. Inclusion criteria for this study required that patients had CT or MRI imaging of the head and neck area within 1 month before CRT and follow-up CT or MRI imaging within 1 year after completion of CRT. Relevant demographic and clinical variables were retrieved from patients’ electronic medical records. THERAPY Chemotherapy regimen consisted of three cycles of intravenous cisplatin-based chemotherapy on days 1, 22 and 43 of CRT. Chemotherapy dose was 100 mg/m 2 . CRT was given in a primary setting for patients with (technical or functional) irresectable LA-HNC and in a postoperative setting in case of positive resection margins and/or in the presence of extranodal tumor ex- tension in resected lymph node metastases. Radiotherapy was administered in 35 fractions of 2 Gy to make a total dose of 70 Gy (primary setting) and in 33 fractions of 2 Gy to make a total dose of 66 Gy (postoperative setting). SKELETAL MUSCLE MEASUREMENTS Skeletal muscle area (SMA) was segmented using the Slice-O-matic software. Patients’ SMA was segmented on pre-CRT imaging and post-CRT imaging. At the level of the third cervical vertebra (C3), a single slice was used for SMA segmentation. The first slide to completely show the entire vertebral arc when scrolling through the C3 vertebra in caudal to cephalic direction was selected. For CT imaging, muscle area was defined as the pixel area between the radi - odensity range of -29 and +150 Hounsfield Units (HU), which is specific for muscle tissue. 23 For MRI, muscle area was manually segmented, and fatty tissue was manually excluded. The overall intraclass correlation coefficient (ICC) for the muscle SMA obtained by CT and MRI has shown to be excellent (ICC 0.9, p<0.01) 24 , and can therefore be used interchangeably for