Application of Dynamic (18)F-FDG PET/CT for Distinguishing Intrapulmonary Metastases from Synchronous Multiple Primary Lung Cancer

It has been a big challenge to distinguish synchronous multiple primary lung cancer (sMPLC) from primary lung cancer with intrapulmonary metastases (IPM). We aimed to assess the clinical application of dynamic (18)F-FDG PET/CT in patients with multiple lung cancer nodules. We enrolled patients with multiple pulmonary nodules who had undergone dynamic (18)F-FDG PET/CT and divided them into sMPLC and IPM groups based on comprehensive features. The SUV(max), fitted K(i) value based on dynamic scanning, and corresponding maximum diameter (D(max)) from the two largest tumors were determined in each patient. We determined the absolute between-tumor difference of SUV(max)/D(max) and K(i)/D(max) (ΔSUV(max)/D(max); ΔK(i)/D(max)) and assessed the between-group differences. Further, the diagnostic accuracy was evaluated by ROC analysis and the correlation between ΔSUV(max)/D(max) and ΔK(i)/D(max) from all groups was determined. There was no significant difference for ΔSUV(max)/D(max) between the IPM and sMPLC groups, while the IPM group had a significantly higher ΔK(i)/D(max) than the sMPLC group. The AUC of ΔK(i)/D(max) for differentiating sMPLC from IPM was 0.80 (cut-off value of K(i) = 0.0059, sensitivity 79%, specificity 75%, p < 0.001). There was a good correlation (Pearson r = 0.91, 95% CI: 0.79-0.96, p < 0.0001) between ΔSUV(max)/D(max) and ΔK(i)/D(max) in the IPM group but not in the sMPLC group (Pearson r = 0.45, p > 0.05). Dynamic (18)F-FDG PET/CT could be a useful tool for distinguishing sMPLC from IPM. K(i) calculation based on Patlak graphic analysis could be more sensitive than SUV(max) in discriminating IPM from sMPLC in patients with multiple lung cancer nodules.