Objective: To evaluate the diagnostic value of PET-CT with (18)F-FDG in preoperative N staging of non-small cell lung cancer (NSCLC), especially the additional value of CT attenuation and the dual-time-point imaging in determining the lymph nodes status.
Methods: Forty-three NSCLC patients underwent curative surgical resection after integrated (18)F-FDG PET-CT examination. The initial scan images were analyzed by two methods. In the first method, the nodal status was determined by (18)F-FDG uptake only (method PET). In the second method, the nodal status was determined by uptake associated with CT attenuation (method PET and CT attenuation). Nodal uptake was interpreted visually and semi quantitatively. For dual-time-point imaging, a retention index (RI) > 10% was regarded as increasing trend. Histopathologic results served as the reference standard.
Results: On the per-nodal-station (group) basis, the diagnostic sensitivity, specificity, accuracy, PPV, and NPV were 88.0%, 88.4%, 88.3%, 59.5% and 97.4%, respectively, by the method 1; 84.0%, 94.6%, 92.9%, 75.0% and 96.8%, respectively, by the method 2. The specificity and accuracy between these two methods had statistically significant difference (P < 0.05). Twenty-eight nodal groups underwent dual-time-point imaging and the differences of DeltaSUV(max) and RI between benign and malignant groups had no statistically significant difference (P > 0.05). Eleven groups were malignant in 23 lymph nodal groups which had an increasing trend. Among the 5 nodal groups which did not show increase in delayed scan, one group was malignant.
Conclusion: (18)F-FDG PET-CT has high diagnostic value in the preoperative N staging of NSCLC, and combining uptake with CT attenuation of lymph nodes can improve the specificity and accuracy. For the lymph nodes with high uptake in the initial scan, increasing uptake in delayed scan has little effect in differential diagnosis, but no increasing in delayed phase is more prone to benign diagnosis.