Value of 18F-FDG PET/CT metabolic parameters of primary lesions for predicting occult lymph node metastasis in lung adenocarcinoma

1044 Objectives: To investigate the predictive value of 18F-fluorodeoxyglucose (FDG) PET/CT metabolic parameters for occult lymph node metastasis (OLM) in lung adenocarcinoma. Methods: A total of 162 patients (56 males, 106 females; age (61.0±8.1) years) who underwent 18F-FDG PET/CT at the Third Affiliated Hospital of Soochow University from January 2013 to December 2018 and preoperatively diagnosed with clinical N0 stage (cN0) were retrospectively enrolled. All patients underwent anatomical pulmonary resection with systematic lymph node dissections within 3 weeks after 18F-FDG PET/CT examinations. According to the presence or absence of lymph node metastasis, patients were divided into OLM[f1] positive (OLM+) group and OLM negative (OLM-) group. Parameters of primary lesions, such as the maximum diameter (Dmax), tumor sites, morphological features, maximum standardized uptake value (SUVmax), mean standardized uptake value (SUVmean), metabolic total volume (MTV), total lesion glycolysis (TLG), tumor SUVmax to liver SUVmean standardized uptake ratio (TLRmax), tumor TLG to liver SUVmean standardized uptake ratio (TLRTLG) were analyzed. Independent sample T test, Mann-Whitney U test and χ2 test were used to compare the parameters between groups. Multivariable logistic regression was used to analyze the independent risk factors for OLM. Receiver operating characteristic (ROC) curve analysis was used to evaluate the diagnostic value of different parameters. Results: Among 162 patients, 21(13.0%) of them were diagnosed as OLM. In OLM+ group, 39 lymph nodes were pathologically positive for metastasis, including 23 N1 disease and 16 N2 disease. Dmax, lobulation, SUVmax, TLG, TLRmax and TLRTLG of the primary lesions in OLM + group were significantly higher than those in OLM-group (all P<0.05). Multivariable logistic regression analysis showed that TLRmax and Dmax were independent risk factors for OLM. TLRmax yielded the highest area under curve (AUC=0.819) with the threshold of 3.12, and the sensitivity, specificity, accuracy, positive predictive value and negative predictive value for predicting OLM were 90.5%, 69.5%, 71.6%, 30.2% and 98.0%, respectively. Conclusions: TLRmax of tumor were independent risk factor for OLM in NSCLC patients. TLRmax could sensitively predict OLM preoperatively in patients with NSCLC.