Value of 18-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) in the differential diagnosis of sarcoidosis and lung cancer with lymph node metastasis: a retrospective study

BACKGROUND: Fluorine 18-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) has been proven to be valuable in guiding the diagnosis and management of sarcoidosis. However, its differential value for sarcoidosis is unclear. The objective of this study was to explore the value of 18F-FDG PET/CT in differentiation sarcoidosis from lung cancer with lymph node metastasis. METHODS: A total of 361 consecutively diagnosed sarcoidosis patients and 1,944 consecutively diagnosed lung cancer patients at Shanghai Pulmonary Hospital were retrospectively reviewed. Among them, 85 patients diagnosed with sarcoidosis and 94 lung cancer patients with lymph node metastasis were enrolled. Demographic data and 18F-FDG PET/CT parameters were analyzed by the chi-square test or independent sample Student’s t-test. Receiver operating characteristic (ROC) curves were generated to identify cut-off values. Multivariate logistic regression was performed to identify independent predictors of sarcoidosis on 18F-FDG PET/CT, and those with P<0.1 were included in a regression model using the forward log rank (LR) method to generate a ROC curve. RESULTS: The ratio of extrapulmonary lymph node involvement in sarcoidosis patients was significantly higher than that in lung cancer patients (64.7% vs. 29.8%, P<0.001). After adjusting for gender and age, extrapulmonary lymph node involvement [odds ratio (OR): 3.160; 95% confidence interval (CI): 1.105–9.035], maximum standardized uptake value (SUVmax) of mediastinum/hilar lymph nodes >13.86 (OR: 3.245; 95% CI: 1.045–10.083), and short axis of the corresponding lymph node >11.5 mm (OR: 5.470; 95% CI: 1.149–26.037) on 18F-FDG PET/CT were independent predictors of sarcoidosis, with a sensitivity and specificity of 77.5% and 69.3%, respectively. The area under the curve was 0.769. CONCLUSIONS: 18F-FDG PET/CT could be helpful to distinguish sarcoidosis from lung cancer patients with lymph node metastasis.