New PET/CT criterion for predicting lymph node metastasis in resectable advanced (stage IB-III) lung cancer: The standard uptake values ratio of ipsilateral/contralateral hilar nodes.

Background: The aim of the present study was to use surgical and histological results to develop a simple noninvasive technique to improve nodal staging using preoperative PET/CT in patients with resectable lung cancer.

Methods: Preoperative PET/CT findings (pStage IB-III 182 patients) and pathological diagnoses after surgical resection were evaluated. Using PET/CT images to determine the standardized uptake value (SUV) ratio, the SUV of a contralateral hilar lymph node (on the side of the chest opposite to the primary tumor) was measured simultaneously. The I/C-SUV ratio was calculated as ipsilateral hilar node SUV/contralateral hilar node SUV. Receiver operating characteristic (ROC) curves were then used to analyze those data.

Results: Based on ROC analyses, the cutoff I/C-SUV ratio for diagnosis of lymph node metastasis was 1.34. With a tumor ipsilateral lymph node SUV ≥2.5, an IC-SUV ratio ≥1.34 had the highest accuracy for predicting N1/N2 metastasis; the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy of nodal staging were 60.66, 85.11, 84.09, 62.5 and 71.29%, respectively.

Conclusions: When diagnosing nodal stage, a lymph node I/C-SUV ratio ≥1.34 can be an effective criterion for determining surgical indications in advanced lung cancer.