Regional nodal staging with ¹⁸F-FDG PET-CT in non-small cell lung cancer: Additional diagnostic value of CT attenuation and dual-time-point imaging

Background: [Fluorine-18]-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET-CT) is widely performed in the regional nodal staging of non-small cell lung cancer (NSCLC). However, the uptake of ¹⁸F-FDG by tubercular granulomatous tissues may lead to false-positive diagnosis. This is of special concern in China, where tubercular granulomatous disease is epidemic. Herein, we evaluated the efficacy of an additional CT attenuation and a dual-time-point scan in determining the status of lymph nodes. Methods: Eighty NSCLC patients underwent curative surgical resection after ¹⁸F-FDG PET-CT and separate breath-hold CT examinations. The initial images were analyzed by two methods. In method 1, nodal status was determined by ¹⁸F-FDG uptake only. In Method 2, nodal status was determined by ¹⁸F-FDG uptake associated with CT attenuation. For dual-time-point imaging, the retention index (RI) of benign and malignant nodal groups with positive uptake in the initial scan was examined. Results: A total of 265 nodal groups were documented. On a per-nodal-group basis, the diagnostic sensitivity, specificity, and accuracy of Method 1 were 66.7%, 89.7%, and 85.3%, respectively, whereas those of Method 2 were 64.7%, 96.7%, and 90.6%, respectively. The improvement in diagnostic specificity and accuracy associated with the addition of CT attenuation in Method 2 as compared to Method 1 was statistically significant (p < 0.01). Thirty-nine nodal groups with positive uptake in the initial scan underwent dual-time-point imaging and the difference in the RI between benign and malignant groups showed no statistical significance (p > 0.05). Conclusion: ¹⁸F-FDG PET-CT has high diagnostic value for preoperative lymph-node (N) staging of NSCLC patients. We show that ¹⁸F-FDG uptake combined with CT attenuation improves the diagnostic specificity and accuracy of nodal diagnosis in NSCLC. For the lymph nodes with positive uptake in the initial scan, dual-time-point imaging has limited effect in differentiation.