Prognostic Value of Tumor-to-Mediastinal Lymph Node SUVmax Ratio on PET/CT in Predicting Nodal Metastasis in Patients with Non-Small Cell Lung Cancer

Abstract

Objective: This study aimed to evaluate the prognostic value of the tumor-to-mediastinal lymph node SUVmax ratio (T/LN SUVmax) compared to the standalone lymph node SUVmax in predicting mediastinal
lymph node metastasis in patients with non-small cell lung cancer (NSCLC).
Methods: A retrospective descriptive study was conducted on 74 NSCLC patients who underwent whole-body 18F-FDG PET/CT prior to surgery, followed by tumor resection and mediastinal lymph node
dissection. A total of 311 mediastinal lymph nodes were identified on PET/CT, of which 178 showed increased FDG uptake. For each suspicious lymph node, both the node’s SUVmax and that of the primary tumor
were recorded to calculate the T/LN SUVmax ratio. Receiver operating characteristic (ROC) analysis was used to compare the diagnostic performance of T/LN SUVmax versus lymph node SUVmax alone and to
determine the optimal cut-off values.
Results: Among the 178 FDG-avid lymph nodes, 32 (17.98%) were confirmed as metastatic by histopathology. The median SUVmax of metastatic nodes was 6.14, significantly higher than that of non-metastatic
nodes (3.14; p < 0.01). A strong correlation was observed between lymph node and tumor SUVmax in metastatic nodes (rs = 0.69; p < 0.001), compared to a weaker correlation in non-metastatic nodes (rs = 0.27;
p = 0.001). The T/LN SUVmax ratio showed superior discriminatory performance, with an optimal cut-off value of 2.45, achieving a sensitivity of 86.3%, specificity of 93.7%, and area under the ROC curve (AUC) of
0.931 (p < 0.001). In contrast, lymph node SUVmax alone, with a cutoff of 4.77, provided a higher sensitivity (93.8%) but lower specificity (76.7%), with an AUC of 0.877 (p < 0.001).
Conclusion: The T/LN SUVmax ratio demonstrated significantly higher accuracy than lymph node SUVmax alone in predicting mediastinal lymph node metastasis in NSCLC. A cut-off value of 2.45 offers high
specificity while maintaining acceptable sensitivity. T/LN SUVmax is a reliable and promising parameter that should be considered in lymph node staging using PET/CT.