Early Multiple Primary Lung Cancer without Fluorodeoxyglucose Uptake on Positron Emission Tomography-Computed Tomography and Displaying Different EGFR Molecular Profiles

Application of Dynamic 18F-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 ¹⁸F-FDG PET/CT in patients with multiple lung cancer nodules. We enrolled patients with multiple pulmonary nodules who had undergone dynamic ¹⁸F-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 ¹⁸F-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.