The maximum standardized uptake value of fluorodeoxyglucose positron emission tomography of the primary tumour is a good predictor of pathological nodal involvement in clinical N0 non-small-cell lung cancer

Objectives: Fluorodeoxyglucose positron emission tomography (FDG-PET) plays an important role in the evaluation of resectable non-small-cell lung cancer (NSCLC). However, this modality cannot be used to detect histological nodal involvement, which can result in stage-migration for resectable lung cancer. In this study, we tried to evaluate the possibility of predicting histological nodal involvement in patients with NSCLC using the maximum standardized uptake value (SUVmax) of FDG-PET of the primary tumour instead of that of the lymph nodes.

Methods: Between February 2008 and September 2011, 898 patients underwent lung cancer surgery at our institute. Among them, we retrospectively analysed 265 patients with clinical N0 NSCLC, who underwent preoperative FDG-PET. The relationships between clinicopathological features, including the findings of FDG-PET and pathological nodal involvement, were investigated. The factors investigated were age, gender, preoperative carcinoembryonic antigen titre, maximum tumour dimension, consolidation/tumour dimension ratio (C/T ratio), SUVmax in the primary tumour and smoking history.

Results: Of the 265 clinical N0 NSCLC patients, 214 (80.8%) had pathological N0 status and 27 (10.2%) and 24 (9.0%) had pathological N1 and N2 disease. In a multivariate analysis, the C/T ratio (P = 0.046) and SUVmax of the primary tumour (P = 0.016) were significant predictors of pathological nodal involvement. With regard to pathological N1-2 disease, the sensitivity, specificity, accuracy and positive and negative predictive values of mediastinal node involvement in patients with NSCLC with an SUVmax for FDG-PET of 10 or more were 49.0, 83.2, 76.6, 41.0 and 87.3%, respectively. Of the 61 patients with NSCLC with an SUVmax for FDG-PET of 10 or more, 25 (41.0%) had pathological N1-2 disease, while only 26 (12.7%) of the remaining 204 patients with an SUVmax for FDG-PET of <10 had nodal disease (P < 0.0001).

Conclusions: Postoperative nodal status was significantly predicted by the SUVmax of FDG-PET of the primary tumour instead of the lymph nodes themselves. The patients with NSCLC in particular who show strong uptake values of SUVmax in the primary tumour could have occult nodal metastases, and may be indicated for a further preoperative modality for an accurate staging.