F-18 FDG PET/CT is useful to identifying metastatic mediastinal lymph node (MLN) involvement in NSCLC patients. However, the accuracy of F-18 FDG PET in nodal staging is substantially reduced by false increases in F-18 FDG uptake in the inflammatory nodes. The efficacy of this technique is controversial because of reactively increased F-18 FDG uptake in the mediastinum, especially in regions endemic for the granulomatous disease. Here, we determined the qualitative and quantitative parameters of F-18 FDG-PET/CT for evaluation of mediastinal nodes to distinguish between malignant and benign lesions.
27 patients with pathologically documented NSCLC who showed bilateral F-18 FDG-avid MLNs on pre-treatment staging PET/CT image were included. 104 MLNs were pathologically analysed through EBUS-TBNA or MLN dissection. The MLN with prominent F-18 FDG uptake compared with other F-18 FDG-avid LNs via visual assessment was qualitatively considered as metastasis. The maximum standardized uptake value (SUVmax) of LN and SUVmax of LN to the liver and blood pool were calculated for quantifying F-18 FDG uptake. SUVmax/contra was obtained to identify metastatic MLNs.
The qualitative evaluation showed sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) for separating metastatic LN from benign reactive hyperplasia of 66.7%, 87.0%, 74.3%, and 88.2%, respectively. SUVmax of LN and normalized SUVmax of LN to the liver and blood pool did not significantly differ; however, SUVmax/contra was significantly higher for metastatic LNs than benign lesions. Receiver-operating-characteristic derived SUVmax/contra cut-off was 1.18 (AUC, 0.734). The quantitative evaluation showed sensitivity, specificity, PPV, and NPV of 66.7%, 75.3%, 77.4%, and 86.4%, respectively.
Qualitative interpretation of F-18 FDG PET/CT was superior to quantitative parameters in discriminating metastatic LNs from benign reactive hyperplasia in patients with bilateral F-18 FDG-avid mediastinal LNs. We suggest SUVmax/contra may aid in the interpretation of mediastinal nodal staging in patients with NSCLC.
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Yun Seong Kim
All authors have declared no conflicts of interest.