Value of FDG PET/CT in the differential diagnosis of benign and malignant hilar mediastinal lymph nodes in patients with non-small cell lung cancer / 中华核医学与分子影像杂志

ABSTRACT

Objective:To investigate the diagnostic value of 18F-fluorodeoxyglucose (FDG) PET/CT in detecting N 1 or N 2 metastasis of lymph node (LN) with different densities in patients with non-small cell lung cancer (NSCLC). Methods:A total of 118 patients (68 males, 50 females, age range 27-87 (65.4±10.8) years) with N 0-N 2 M 0 NSCLC in Beijing Hospital between October 2007 and December 2017 were included in this study. All patients underwent 18F-FDG PET/CT, followed by surgery within 1 month. The pathological findings of the resected hilar mediastinal LN were taken as the gold standard, and ratios of LN metastasis were calculated for different density groups (calcification, partial calcification, hyper density, hypodensity/isodensity). The cut-off values of LN size (short diameter) and the maximum standardized uptake value (SUV max) in the detection of N 1 and N 2 metastases was determined by the receiver operating characteristic (ROC) curve, and the diagnostic efficiencies were calculated. Independent-sample t test, Mann-Whitney U test and χ2 test (partition of χ2) were used for data analysis. Results:A total of 433 LN has the histopathologic results: 365 LN was in stage N 0, 68 LN was in stage N 1-N 2. There were no metastases in calcification group (0/8). The metastatic LN proportions in partial calcification group (28.6%, 8/28), hypodensity/isodensity group (20.3%, 44/217) were significantly higher than that in the hyper density group (8.9%, 16/180; χ2 values 7.369, 9.945, both P<0.017 (threshold for partition of χ2)). There was no significant difference between the partial group and hypodensity/isodensity group ( χ2=1.021, P>0.017). The SUV max of N 1+ N 2 group was significantly higher than that in N 0 group (6.94 (4.51, 11.36) vs 2.45 (1.93, 3.42); z=-10.388, P<0.01). According to the ROC curve, the cut-off value of SUV max in detecting hilar and mediastinal LN was 3.66. The diagnostic sensitivity, specificity and accuracy for N 1+ N 2 metastasis was 85.3%, 78.9%, 80.0% respectively. The cut-off values of SUV max for hypodensity/isodensity group and hyper density group were 3.66 and 2.79 respectively, and the corresponding sensitivities, specificities, accuracies and positive predictive values (PPV) were 93.2%, 86.7%, 88.0%, 64.1% vs 93.8%, 57.9% ( χ2=10.724), 61.1% ( χ2=7.326, P<0.01), 17.9%( χ2=32.971, P<0.01). The specificity of LN size (1.0 cm)+ SUV max was significantly higher that of LN size or SUV max alone (94.2% vs 80.9%, 86.7%; χ2 values 14.048, 5.661, both P<0.05) in hypodensity/isodensity group. The specificity and accuracy of LN size (1.0 cm)+ SUV max were significantly higher those of SUV max alone ( χ2 values 58.043, 37.037, both P<0.01) in hyper density group. Conclusions:18F-FDG PET/CT is useful in diagnosing the N 1+ N 2 metastases in hypodensity/isodensity LN, but has limitation in diagnosing the partial calcification LN. Combination of lymph node short diameter and SUV max cut-off value can improve the diagnostic specificity or accuracy of 18F-FDG PET/CT for hypodensity/isodensity and high density LN.