DIAGNOSTIC ACCURACY OF FDG-PET/CT AND MRI FOR THE DETECTION OF T1-T2 HNSCC

626 Objectives Head and neck squamous cell carcinoma (HNSCC) classified T1-T2 regarding WHO classification are more difficult to detect by conventional imaging than higher stage tumours due to their small size. It remains however a diagnostic challenge in the therapeutic management of patients. The aim of this study was also to assess and compare the diagnostic accuracy of FDG-PET/CT and MRI to detect T1-T2 HNSCC. Methods Thirty-five consecutive patients with histologically proven T1-T2 HNSCC were retrospectively included. All patients underwent pre-therapeutic FDG-PET/CT and MRI. Two nuclear medicine physicians and 2 radiologists blindly reviewed all FDG-PET/CT and MRI, respectively. A 5-points qualitative scale was used to estimate tumour detection ability. Sensitivity of each modality was compared together using a McNemar test. SUVmax in FDG-PET/CT and gadolinium enhancement (GE) in MRI of each tumour were recorded and compared with T stage using a Mann-Whitney test. Inter-observer variability was assessed by Kappa index (k) of Cohen statistics. Results Among the 35 tumours, 29 were detected by FDG-PET/CT and 22 by MRI. MRI detected none of the 6 lesions incorrectly identified by FDG-PET/CT. FDG-PET/CT correctly identified 7 of the 13 MRI false negative results. The sensitivity of FDG-PET/CT (83%) was significantly higher than those of MRI (63%) (p= 0.015). There was no significant correlation between T staging and SUVmax (p=0.16) or GE (p=0.97). Inter-observer analysis revealed respectively a good (k=0.73) and a moderate agreement (k=0.53) for PET-CT and MRI interpretation. Conclusions Our study showed a higher diagnostic accuracy of FDG-PET/CT than MRI to detect T1-T2 HNSCC with a good inter-observer agreement.