18F-FDG PET and CT/MRI in oral cavity squamous cell carcinoma: a prospective study of 124 patients with histologic correlation.

Accurate evaluation of primary tumors and cervical lymph node status of squamous cell carcinoma (SCC) of the oral cavity is important to treatment planning and prognosis prediction. In this prospective study, we evaluated the use of 18F-FDG PET, CT/MRI, and their visual correlation for the identification of primary tumors and cervical nodal metastases of SCC of the oral cavity with histologic correlation. METHODS: One hundred twenty-four patients with pathologically proven diagnoses of oral cavity SCC underwent 18F-FDG PET and CT/MRI within 2 wk before surgery. We interpreted 18F-FDG PET, CT/MRI, and visually correlated 18F-FDG PET and CT/MRI separately to assess the primary tumors and their regional lymph node status. We recorded lymph node metastases according to the neck level system of imaging-based nodal classification. Histopathologic analysis was used as the gold standard for assessment of the primary tumors and lymph node involvement. We analyzed differences in sensitivity and specificity among the imaging modalities using the McNemar test. The receiver-operating-characteristic (ROC) curve and calculation of the area under the curve were used to evaluate their discriminative power. RESULTS: The accuracy of 18F-FDG PET, CT/MRI, and their visual correlation for the identification of primary tumors was 98.4%, 87.1%, and 99.2%, respectively. The sensitivity of 18F-FDG PET for the identification of nodal metastases on a level-by-level basis was 22.1% higher than that of CT/MRI (74.7% vs. 52.6%, P < 0.001), whereas the specificity of 18F-FDG PET was 1.5% lower than that of CT/MRI (93.0% vs. 94.5%, P = 0.345). The sensitivity and specificity of the visual correlation of 18F-FDG PET and CT/MRI were 3.2% and 1.5% higher than those of 18F-FDG PET alone (77.9% vs. 74.7%, P = 0.25; 94.5% vs. 93.0%, P = 0.18, respectively). The area under the curve obtained from the ROC curve showed that 18F-FDG PET was significantly superior to CT/MRI for total nodal detection (0.896 vs. 0.801, P = 0.002), whereas the visual correlation of 18F-FDG PET and CT/MRI was modestly superior to 18F-FDG PET alone (0.913 vs. 0.896, P = 0.28). CONCLUSION: 18F-FDG PET is superior to CT/MRI in the detection of cervical status of oral cavity SCC. The sensitivity of 18F-FDG PET for the detection of cervical nodal metastasis on a level-by-level basis was significantly higher than that of CT/MRI, whereas their specificities appeared to be similar. Visual correlation of 18F-FDG PET and CT/MRI showed a trend of increased diagnostic accuracy over 18F-FDG PET alone but without a statistically significant difference, and its sensitivity was still not high enough to replace pathologic lymph node staging based on neck dissection.