The value of dual time point 18F-FDG PET/CT imaging in differentiating lymph node metastasis from reactive hyperplasia in bladder urothelial carcinoma

Abstract Purpose Our study explored the clinical value of dual time point FDG PET imaging for differentiating lymph node metastasis from lymph node reactive hyperplasia. Methods The study analyzed 250 lymph nodes from bladder cancer patients. All patients underwent 18F-FDG PET/CT delayed diuretic imaging. Metabolic parameters SUVmax, SUVmean, MTV, and related delay indices before and after PET delayed imaging were obtained. Relationships with outcomes were analyzed using nonparametric analysis and multivariate analysis. ROC curves and nomograms were drawn to predict lymph node metastasis. Results Delayed PET/CT imaging helps to detect more suspicious lymph nodes. If SUVmax = 2.0 or 2.5 was taken as cut-off, delayed imaging could increase the detection rate of metastatic lymph nodes by 4.1%, and 6.9%, respectively. Reactive hyperplasia lymph nodes were more likely to show increased lymph node-localized FDG uptake than metastatic lymph nodes on delayed FDG imaging. Metastatic lymph nodes were more likely to have whole, diffuse increased FDG uptake on delayed imaging. Short lymph node diameter, SUVmean, and DIMTV were three independent predictors for differentiating metastatic lymph nodes from reactive hyperplasia. Lymph node metastasis could be better differentiated from inflammatory hyperplasia ones by the combination of these three predictors. In high-risk patients, the probability of lymph node metastasis is as high as 97.6%. Conclusions Dual time point imaging is helpful to detect more suspicious lymph nodes. Some hyperplasic lymph nodes had certain image characteristics using delayed imaging. Short lymph node diameter, SUVmean, and DIMTV were three important parameters for predicting lymph node metastasis.