Improved detection of metastatic lymph nodes in oesophageal squamous cell carcinoma by combined interpretation of fluorine-18-fluorodeoxyglucose positron-emission tomography/computed tomography

BACKGROUND: We sought to evaluate the diagnostic performance of fluorine-18-fluorodeoxyglucose positron-emission tomography/computed tomography ((18)F-FDG PET/CT) in the detection of metastatic lymph nodes by combined interpretation of PET/CT images in patients with oesophageal squamous cell carcinoma. METHODS: Two hundred three patients with oesophageal squamous cell carcinoma underwent (18)F-FDG PET/CT before oesophagectomy and lymph node dissection. Maximum standardized uptake value (SUV(max)), mean Hounsfield unit (HU), short axis diameter (size), and visual CT attenuation (high, iso-, low) were evaluated on noncontrast CT and PET images following PET/CT scan. In this combined interpretation protocol, the high attenuated lymph nodes were considered benign, even if the SUV(max) value was high. The diagnostic accuracy of each method was compared using the postoperative histologic result as a reference standard. RESULTS: A total of 1099 nodal stations were dissected and 949 nodal stations were proven to demonstrate metastasis. SUV(max) and size of the malignant lymph nodes were higher than those of the benign nodes, and visual CT attenuation was significantly different among the two groups (P < 0.001). Using cutoff values of 2.6 for SUV(max) and 10.2 mm for size, the combined interpretation of an SUV(max) of more than 2.6 with iso- or low CT attenuation [area under the curve (AUC): 0.846, 95% confidence interval (CI): 0.824–0.867] showed significantly better diagnostic performance for detecting malignant lymph nodes than SUV(max) only (AUC: 0.791, 95% CI: 0.766–0.815) and size (AUC: 0.693, 95% CI: 0.665–0.720) methods (P < 0.001) in a receiver operating characteristic curve analysis. CONCLUSIONS: The diagnostic accuracy of PET/CT for nodal metastasis in oesophageal squamous cell carcinoma was improved by the combined interpretation of (18)F-FDG uptake and visual CT attenuation pattern.