Is FDG-PET/CT Scan Useful in the Detection of Subcentimeter Mediastinal Lymph Node Involvement in Patients With Lung Carcinoma?

Background Early staging of lung carcinoma (CA) is pivotal in planning the treatment. Lymph node metastasis can be detected by imaging and invasive procedures. The 18F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) is an emerging noninvasive imaging modality in detecting nodal metastasis. Objective This study aimed to determine the usefulness of the FDG-PET/CT scan in detecting subcentimeter mediastinal lymph node involvement in lung CA patients by taking histopathology as the gold standard. Materials and methods We conducted a retrospective cross-sectional study at a tertiary care cancer hospital in Pakistan over four and half years, from January 2015 to June 2019. All patients suffering from non-small cell lung CA (NSCLC) having avid subcentimeter nodes on FDG-PET/CT were included. The findings obtained on FDG-PET/CT were correlated with histopathological findings after endobronchial ultrasound (EBUS). The results were formulated using IBM SPSS Statistics for Windows, Version 21 (Released 2012; IBM Corp., Armonk, New York, United States). Results Results showed that 42/380 total lung CA patients had avid subcentimeter lymph nodes obtained on FDG-PET/CT. A total of 22/42 (52.4%) lymph nodes appeared to be benign, and 20/42 (47.6%) lesions were malignant on histopathology. FDG-PET/CT sensitivity is calculated to be 95%, specificity is 68%, positive predictive value is 73%, negative predictive value is 94%, and accuracy is 80.9%. Using the receiver operating characteristic (ROC) curve, sensitivity and specificity were seen in nodes of size 7.5 mm and the maximum standardized uptake value (SUV max) of 5.5 as cutoff values as manifested by area under the curve (AUC). Conclusion FDG-PET/CT was proven to have high sensitivity and accuracy but a low specificity rate to detect nodal involvement in lung CA patients. The high false-positive rates are mainly due to increased prevalence of endemic lung infectious disease.