Improving Diagnostic Accuracy for Malignant Nodes and N Staging in

Purpose: We investigated prospectively whether the interpretation considering the patterns of FDG uptake and the findings of unenhanced CT for attenuation correction can improve the diagnostic accuracy for assessing malignant lymph node (LN) and N stage in non-small cell lung cancer (NSCLC) using CT-corrected FDG-PET (PET/CT). Materials & Methods: Subjects were 91 NSCLC patients (M/F: 62/29, age: 60±9 yr) who underwent PET/CT before LN dissection. We evaluated the maximum SUV (maxSUV), patterns of FDG uptake, short axis diameter, and calcification of LN showing abnormally increased FDG uptake. Then we investigated criteria improving the diagnostic accuracy and correlated results with postoperative pathology. In step 1, LN was classified as benign or malignant based on maxSUV only. In step 2, LN was regarded as benign if it had lower maxSUV than the cut-off value of step 1 or it had calcification irrespective of its maxSUV. In step 3, LN regarded as malignant in step 2 was classified as benign if they had indiscrete margin of FDG uptake. Results: Among 432 LN groups surgically resected (28 malignant, 404 benign), 71 showed abnormally increased FDG uptake. We determined the cut-off as maxSUV = 3.5 using ROC curve analysis. The sensitivity, specificity, and accuracy for assessing malignant LN were 64.3%, 86.9%, 85.4 % in step 1, 64.3%, 95.0%, 93.1 % in step 2, and 57.1%, 98.0%, 95.4 % i