Objective To explore the clinical value of ¹⁸F-fluorodeoxyglucose (FDG) PET/CT metabolic parameters in the prediction of mediastinal lymph node metastasis in patients with non-small cell lung cancer (NSCLC).

Methods A total of 102 patients with NSCLC histopathologically confirmed from January 2018 to March 2021 in Fuyang People's Hospital were restrospectively analyzed in this study. The patients consisted of 59 males and 43 females aged 33–90 (66.0±11.2) years. All patients underwent ¹⁸F-FDG PET/CT imaging before operation to analyze and calculate the metabolic parameters. The coefficient of variation (CV) is the ratio of the standard deviation (SD) of the maximum standardized uptake value (SUV_max) to SUV_max of the lesion; LMV is the ratio of the SUV_max of the lymph node to the mean standardized uptake value (SUV_mean) of the mediastinal blood pool; the total lesion glycolysis (TLG) is the product of metabolic tumor volume (MTV) and SUV_mean. The receiver operator characteristic (ROC) curve was drawn to determine the optimal cut-off value for predicting lymph node metastasis and calculate the sensitivity and specificity. Enumeration data were evaluated using χ² test or Fisher's exact probability method, and continuous measurement data were compared using independent-sample t test. Univariate and multivariate Logistic regression analysis were used in screening the predictors of lymph node metastasis.

Results The univariate Logistic regression analysis results showed that when the long diameter of the lung primary tumor was over 30.0 mm or the short diameter of the lymph nodes was over 10.0 mm, lymph node metastasis was likely to occur (61.9% vs. 38.1%, 59.5% vs. 40.5%; χ²=9.16, 5.20; both P<0.05); the CV of the primary tumor and the SUV_max and LMV of lymph nodes of patients with lymph node metastasis were higher than those of patients without lymph node metastasis (46.7±6.1 vs. 29.4±6.0, 5.9±1.9 vs. 2.8±1.6, 2.2±0.6 vs. 1.4±0.3; t=13.81, 8.60, 3.97; all P<0.05). The multivariate Logistic regression analysis results suggested that the SUV_max of lymph nodes (OR=2.2, 95% confidence interval (CI): 1.30–3.80, P<0.05) and the CV of the primary tumor (OR=1.5, 95%CI: 1.20–1.80, P<0.01) were independent risk factors affecting the status of lymph node metastasis. The ROC curve analysis results showed that the area under the CV curve of the primary tumor was 0.97 (SD=0.02, 95%CI: 0.94–0.99, P<0.01). When CV>30.5, the sensitivity of diagnosis of lymph node metastasis was 97.5%, and the specificity was 41.7%. The area under the curve of lymph node SUV_max was 0.91 (SD=0.30, 95%CI: 0.85–0.97, P<0.01). When the lymph node SUV_max>3.1, the sensitivity and specificity of the diagnosis of lymph node metastasis were 95.2% and 23.3%, respectively. The combined diagnosis of the two risk factors resulted in an area under the curve of 0.98 (SD=0.01, 95%CI: 0.96–1.00, P<0.01).

Conclusion Among the metabolic parameters of ¹⁸F-FDG PET/CT, the CV of the primary tumor and the SUV_max of lymph nodes are independent risk factors for predicting mediastinal lymph node metastasis in patients with NSCLC and can provide useful information for treatment.