Primary tumor PET/CT [¹⁸F]FDG uptake is an independent predictive factor for regional lymph node metastasis in patients with non-small cell lung cancer

Abstract

Aim: To investigate the correlation between [¹⁸F]fluorodeoxyglucose (FDG) uptake in a primary tumor and pathologic N stages, and to further analyze the possible risk factors contributing to the regional lymph node metastasis.

Patients and methods: Eighty patients with non-small cell lung cancer (NSCLC) who underwent positron emission tomography/computed tomography were enrolled in the study. The FDG uptake in the primary tumor was compared for the different N staging groups and further correlation was performed. The degree of FDG uptake in the primary tumor and other possible variables related to the incidence of lymph node metastasis were examined by univariate and logistic multivariate analysis. FDG uptake was quantitated using the maximum standardized uptake value (SUVmax).

Results: Statistically significant differences were found in the SUVmax of the primary tumors among different N staging groups (F = 4.124, P = 0.023), and the correlation between them was also statistically significant (r = 0.438, P = 0.000). Univariate analysis showed that blood tumor markers, primary tumor size, histologic grade, and SUVmax of the primary tumor were significantly associated with lymph node involvement. Logistic multivariate analysis showed that blood tumor makers and SUVmax of primary tumor might be considered as significant predictive factors for lymph node metastasis in patients with NSCLC.

Conclusion: Our results show that there is a significant relationship between the SUVmax of the primary tumor and the pathologic N stage of NSCLC. FDG uptake by the primary tumor may be an independent predictor of regional lymph node metastasis in patients with NSCLC.

Figure 1

A 67-year-old woman, with blood CEA of 14.95 ng/ml, was diagnosed with poorly differentiated adenocarcinoma in the inferior lobe of the left lung. Three different slices of integrated FDG-PET/CT images (A–C) and maximum intensity projection showed an SUV_max of the primary tumor of 9.4. Although there was no obvious mediastinal lymph nodal metastasis on imaging, the high SUV_max of the primary tumor and CEA level indicated that the patient might be at risk for lymph nodal metastasis. Pathologic results after surgery showed micro-metastases in subaortic and subcarinal lymph nodes (N2).