Objectives: Positron emission tomography with 2-[18F] fluoro-2-deoxy-D-glucose as a tracer and computed tomography (FDG-PET/CT) are utilized for the diagnosis of lymph node (LN) metastasis from lung cancer. In this study, we analyzed the diagnostic ability of FDG-PET for N staging by focusing on the clinical features of false-positive (FP) and false-negative (FN) cases.
Methods: From March 2006 to February 2010, 112 patients underwent preoperative examinations using FDG-PET/CT followed by radical resection with hilar and mediastinal dissection. We analyzed their clinicopathological characteristics based on preoperative FDG-PET/CT findings and post-operative histopathological diagnosis of resected LNs.
Results: Based on the PET/CT results, 17 patients were misdiagnosed (9 FN and 8 FP). The sensitivity, specificity, accuracy and negative and positive predictive values for N1/N2 were 50.0, 94.5, 84.0, 93.0 and 58.3%, respectively, whereas those for N2 were 57.8, 90.3, 84.8, 90.3 and 61.1%, respectively. FP findings more frequently occurred in cases with elevated white blood cell (WBC) count (P=0.015) and smokers (P=0.04). In the FN group, the maximum standardized uptake value for the primary tumour was lower than that in the true-positive (TP) group (P=0.01). The short-axis sizes of 71 LNs differently diagnosed by PET/CT and histopathology findings were significantly smaller in the FN group than the TP group (P<0.001), whereas there was no difference between TP and FP. As for FN LNs in the TP group, there was no significant difference.
Conclusions: PET/CT showed a good ability to detect metastatic LNs, especially for N2 diagnosis. However, there were some limitations, especially in cases with elevated peripheral WBC count and/or smoking history.