Exploration of the evolving role of ¹⁸ F-FDG PET/CT in evaluating extrahepatic cholangiocarcinoma lymph node metastasis.

e16218 Background: The presence of lymph node metastases at diagnosis is one of the most relevant negative prognostic factors in patients with extrahepatic cholangiocarcinoma (eCCA). This study aims to identify the diagnostic criteria of 18 F-FDG PET/CT for lymph node metastasis in eCCA, and to develop a more accurate predictive model of lymph node metastasis based on these results. Methods: All pathologically diagnosed cases of 98 lymph nodes from 71 patients of extrahepatic cholangiocarcinoma preoperatively were retrospectively analyzed. The distributional differences between malignant and benign groups were compared. The variables for constructing the metastasis prediction model of the lymph nodes were determined through further univariate and multivariate analyses of the variables exhibiting distributional differences. Results: It was observed that lymph nodes with tumor metastasis displayed greater size and metabolism. Following multifactorial analysis, a lymph node metastasis prediction model comprising of three variables: short diameter, aspect ratio and SUVmax. This model demonstrated favorable outcomes in our cohort's validation (AUC 0.932, sensitivity 87.5%, specificity 90.3%). In addition, these factors were used to construct the nomogram model, which showed good concordance and accuracy. Conclusions: In this study, a lymph node metastasis prediction model for extrahepatic cholangiocarcinoma based on short diameter, aspect ratio, and SUVmax has been developed. However, a larger sample size and a multicenter study are necessary to authenticate the model's efficacy.