Lymph node to primary tumor SUV ratio as a valuable parameter on [ 18 F]FDG PET/CT in non-small cell lung cancer nodal staging.

Introduction: Accurate lymph node staging is essential for treatment planning and prognosis in non-small cell lung cancer (NSCLC). [ 18 F]Fluorodeoxyglucose Positron emission tomography/computed tomography ([ 18 F]FDG PET/CT) is a widely used non-invasive imaging modality. Lymph node size and maximum standardized uptake value (SUVmax) are the most utilized parameters but with known limitations. We hypothesized the lymph node-to-primary tumor SUVmax ratio (N/T SUV ratio) could mitigate the limitations and provide a more reliable diagnostic measure.

Objective: This study aims to evaluate the diagnostic accuracy of the N/T SUV ratio in comparison to other PET/CT parameters.

Materials and methods: This retrospective study evaluated consecutive patients with [ 18 F]FDG PET/CT done in Tuen Mun Hospital, Hong Kong between January 2023 and December 2023. PET/CT parameters, including SUVmax, N/T SUV ratio, visual score, and lymph node size, were analyzed. Receiver operating characteristic curves were used to determine optimal diagnostic cutoffs. Subgroup analyses were conducted based on lymph node and primary tumor characteristics.

Results: A total of 62 patients with 98 histologically confirmed lymph nodes were included. N/T SUV ratio (cutoff: 0.5) demonstrated the highest diagnostic accuracy (area under curves: 0.924), with a sensitivity of 82.69% and specificity of 95.65%. It remained consistent across patient subgroups and outperformed SUVmax, visual score, and lymph node size in distinguishing metastatic from benign nodes.

Conclusion: N/T SUV ratio (cutoff: 0.5) demonstrates the best consistency and robustness across patient subgroups, mitigating SUVmax variability. Its simplicity and reproducibility make it a valuable parameter for NSCLC nodal staging. Further studies with larger, multicenter prospective cohorts are warranted to validate its application.