Relative value of ultrasound, computed tomography and positron emission tomography imaging in the clinically node-negative neck in oral cancer

Aim: To determine the most accurate noninvasive imaging modality for occult metastasis in clinically node-negative necks in oral squamous cell carcinoma from a granulomatous disease endemic region. Method: Prospective, observational study comparing ultrasound ( US), contrast enhanced computed tomography ( CECT) and positron emission tomography-computed tomography ( PET-CT). Level wise assessment of neck nodes with each imaging modality was performed and compared with final histopathology. Results: Eighty-five necks were evaluated in 70 patients. Sensitivity, specificity and accuracy of the three modalities were 78.9, 68.75 and 73.25% for US, 73.6, 85.4 and 80.2% for CECT, and 81.5, 54.1 and 66.2% for PET-CT, respectively. CECT performed better than US and PET-CT scan particularly in levels IB and II ( accuracy of 81.4 and 88.3% for CECT, 73.25 and 79.1% for US, and 68.6 and 68.6% for PET-CT scan, respectively). Concordance with histology was best with CECT (kappa = 0.615) followed by US (kappa = 0.461) and PET-CT (kappa = 0.337). Conclusion: The quest for the most accurate imaging modality in clinically node-negative necks continues. US alone is inadequate. While PET-CT may not be a specific imaging modality in detecting occult cervical nodal metastasis in endemic regions of chronic granulomatous diseases, the performance of PET CECT in this setting remains to be evaluated. CECT scan, routinely used in imaging for primary disease, is fairly accurate in detecting nodal metastasis. However, in early oral cancers that are generally treated without any imaging for the primary tumor, management of the neck will largely depend on clinical judgment.