The value of dual-energy computed tomography quantitative parameters in differentiating the sensitivity of small lymph nodes to chemoradiotherapy in nasopharyngeal carcinoma

PURPOSE: To evaluate the value of dual-energy computed tomography (DECT) quantitative parameters in differentiating the sensitivity of small lymph nodes (short-axis diameter 5-9 mm) that are negative on magnetic resonance imaging (MRI) to chemoradiotherapy in patients with nasopharyngeal carcinoma (NPC). METHODS: Newly diagnosed NPC patients underwent DECT before treatment. The reference standard was the radiographic regression status of lymph nodes at 1 year after radiotherapy. They were classified into the effective disease (ED) group and the stable disease (SD) group based on their sensitivity to chemoradiotherapy. The characteristics of small lymph nodes, DECT parameters, and diagnostic value were compared. RESULTS: One year after radiotherapy, 65 and 60 small lymph nodes were detected in the ED and SD groups, respectively; the proportion of small lymph nodes in the lower neck was higher in the ED group than in the SD group, and all such nodes achieved complete response (CR). Normalized iodine concentration (NIC), and slope of the energy spectrum (λHU) were independent risk factors for differentiating the sensitivity of small lymph nodes to chemoradiotherapy (P < 0.05). In the venous phase, λHU demonstrated the strongest diagnostic performance among all DECT parameters, with an area under the curve (AUC) of 0.803 and an optimal cutoff value of 4.465. The diagnostic power of the combined parameters was higher, especially when the short-axis diameter of small lymph nodes was 7-9 mm, the location was in the lower neck, and λHU was > 4.46 in the venous phase; the diagnostic power AUC of the combined parameters reached 0.870. CONCLUSION: DECT quantitative parameters can effectively assess the sensitivity to chemoradiotherapy of MRI-negative small lymph nodes in NPC and aid in evaluating metastatic risk. λHU in the venous phase is the most reliable single DECT parameter. Combining short-axis diameter and nodal region provides an optimized reference for metastatic risk assessment of small lymph nodes.