Metabolic tumor heterogeneity analysis by F-18 FDG PET/CT predicts mediastinal lymph node metastasis in non-small cell lung cancer patients with clinically suspected N2

Objectives: Accurate prediction of pathological N2 metastasis is crucial for choosing the best therapeutic strategy for non-small cell lung cancer (NSCLC) patients. The aim of this study is to evaluate the usefulness of metabolic heterogeneity assessed by the positron emission tomography combined with computed tomography (PET/CT) using F-18 fluorodeoxyglucose (FDG) in primary NSCLC with clinically suspected N2 metastasis in predicting pathological mediastinal lymph node metastasis. Materials and methods: Fifty patients with newly diagnosed NSCLC and clinically suspected N2 on preoperative CT and F-18 FDG PET/CT were included. Pathological results were confirmed by surgical specimens and the coefficient of variation (COV) was used to evaluate the metabolic heterogeneity of primary tumor mass by using F-18 FDG PET/CT. Results: Among the 50 patients with clinically suspected N2, 23 patients were pathologically confirmed as positive mediastinal lymph node metastasis and 27 patients were negative. Pathologically confirmed positive mediastinal lymph node metastasis group presented higher COV than the negative metastasis group (p < 0.001). An optimal cut-off value of 41.9 was proposed for discriminating metastasis from non-metastasis group. The sensitivity and specificity were 65.2% and 88.9%, respectively (AUC: 0.84; p < 0.0001). In addition, compared with other metabolic parameters, metabolic heterogeneity defined as COV showed the superior predictability of the mediastinal metastasis. (p = 0.001) Conclusion: Metabolic heterogeneity which was defined as COV of primary tumor could predict pathological mediastinal lymph node metastasis in NSCLC patients with clinically suspected N2. Therefore, COV of primary tumor may play a complementary role to conventional imaging in providing nodal information before taking biopsy.