Preoperative diagnosis of lymph node metastases of colorectal cancer by FDG-PET/CT

Purpose: The purpose of this study was to assess the diagnostic value of 18F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) for lymph node (LN) metastasis of colorectal cancer. Methods: FDG-PET/CT was used to preoperatively evaluate 88 patients with colorectal cancer. In this study, LN sites were divided into proximal and distant according to their distance from the primary tumor. The FDG-PET/CT images were evaluated by three criteria; nodal diameter, abnormal uptake and maximum standardized uptake value (SUV). We compared the diagnostic ability of these methods for LN metastasis at proximal and distant sites. Results: The mean SUV of the malignant LNs was significantly higher than that of the benign LNs. The sensitivity, specificity and accuracy of diagnosis by abnormal uptake were 28.6, 92.9 and 75.0%, those by nodal diameter using cutoff value of 10 mm were 30.6, 95.3 and 74.4% and those by SUV using cutoff value of 1.5 were 53.1, 90.6 and 80.1%, respectively. The sensitivity, specificity and accuracy of diagnosis based on optimal SUV were 51.2, 85.1 and 69.3% in the proximal site and 62.5, 92.5 and 89.7%, respectively, in the distant site. Conclusions: FDG-PET/CT is useful for preoperative diagnosis of distant LN metastases of colorectal cancers.