In this study, we examined whether additional, delayed regional FDG PET scans could increase the accuracy of the lymph node staging of NSCLC patients.

Among 87 patients who underwent open thoracotomy or mediastinoscopic biopsy under the suspicion of NSCLC, 35 (32 NSCLC and 3 infectious diseases) who had visible lymph nodes on both preoperative whole body scan and regional FDG PET scan were included. The following 3 calculations were made for each biopsy-proven, visible lymph node: maximum SUV of whole body scan (WB SUV), maximum SUV of delayed chest regional scan (Reg SUV), and the percent change of SUV between WB and regional scans (% SUV Change). ROC curve analyses were performed for WB SUVs, Reg SUVs and % SUV Changes.

Seventy lymph nodes (29 benign, 41 malignant) were visible on both preoperative whole bodyscan and regional scan. The means of WB SUVs, Reg SUVs and % SUV Changes of the 41 malignant nodes, 3.71±1.08, 5.18±1.60, and 42.59±33.41%, respectively, were all significantly higher than those of the 29 benign nodes, 2.45±0.73, 3.00±0.89, and 22.71±20.17%, respectively. ROC curve analysis gave sensitivity and specificity values of 80.5% and 82.8% at a cutoff of 2.89 (AUC 0.839) for WB SUVs, 87.8% and 82.8% at a cutoff of 3.61 (AUC 0.891) for Reg SUVs, and 87.8% and 41.4% at a cutoff of 12.3% (AUC 0.671) for % SUV Changes.

Additional, delayed regional FDG PET scans may improve the accuracy of lymph node staging of whole body FDG PET scan by providing additional criteria of Reg SUV and % SUV Change.