18F-FDG PET/CT and contrast-enhanced CT evaluation of lymph node status after neoadjuvant immunochemotherapy in patients with esophageal squamous cell carcinoma.

PURPOSE To assess the detectability of residual tumor-involved lymph nodes (LNs) using 18F-FDG PET/CT and contrast-enhanced CT (CECT) parameters in patients with esophageal squamous cell carcinoma (ESCC) following neoadjuvant immunochemotherapy (NICT). METHODS This retrospective study analyzed 161 ESCC patients who received esophagectomy following NICT. All patients underwent preoperative 18F-FDG PET/CT, and 137 also received CECT. Metastatic and nonmetastatic LNs, confirmed pathologically, were evaluated according to the Japanese Esophageal Society (JES) staging system. Diagnostic accuracy was assessed using receiver operating characteristic (ROC) curve analysis and logistic regression was used to integrate metrics for the prediction of LNs status. RESULTS For overall lymph node analysis, there was no significant difference in diagnostic performance between the optimal PET parameter, total lesion glycolysis (TLG), and the best CECT parameter, short-axis diameter (SAD) (AUC: 0.830 vs. 0.797, P = 0.08). Nevertheless, a combined model incorporating TLG and SAD of PET/CT demonstrated significantly superior diagnostic performance compared to SAD of CECT (AUC: 0.863 vs. 0.797, P < 0.001). In subregional analyses, TLG performed best in the paraesophageal group and abdominal area, with AUCs of 0.824 and 0.857. The SUVmax ratio of lymph nodes to liver blood pool (LLR) demonstrated the highest diagnostic performance in the recurrent nerve group and subcarinal area, with AUCs of 0.885 and 0.884, respectively. CONCLUSION 18F-FDG PET/CT is superior to CECT in assessing LNs status in ESCC patients after NICT. The optimal predictive parameters and thresholds vary across LN regions, underscoring the importance of region-specific diagnostic criteria.