Clinical Value of a One-Stop-Shop Low-Dose Lung Screening Combined with ¹⁸F-FDG PET/CT for the Detection of Metastatic Lung Nodules from Colorectal Cancer

Purpose: The aim of this study was to evaluate the clinical usefulness of additional low-dose high-resolution lung computed tomography (LD-HRCT) combined with ¹⁸F-fluoro-2-deoxyglucose positron emission tomography with CT (¹⁸F-FDG PET/CT) compared with conventional lung setting image of ¹⁸F-FDG PET/CT for the detection of metastatic lung nodules from colorectal cancer. Methods: From January 2011 to September 2011, 649 patients with colorectal cancer underwent additional LD-HRCT at maximum inspiration combined with ¹⁸F-FDG PET/CT. Forty-five patients were finally diagnosed to have lung metastasis based on histopathologic study or clinical follow-up. Twenty-five of the 45 patients had ≤5 metastatic lung nodules and the other 20 patients had >5 metastatic nodules. One hundred and twenty nodules in the 25 patients with ≤5 nodules were evaluated by conventional lung setting image of ¹⁸F-FDG PET/CT and by additional LD-HRCT respectively. Sensitivities, specificities, diagnostic accuracies, positive predictive values (PPVs), and negative predictive values (NPVs) of conventional lung setting image of ¹⁸F-FDG PET/CT and additional LD-HRCT were calculated using standard formulae. The McNemar test and receiver-operating characteristic (ROC) analysis were performed. Results: Of the 120 nodules in the 25 patients with ≤5 metastatic lung nodules, 66 nodules were diagnosed as metastatic. Eleven of the 66 nodules were confirmed histopathologically and the others were diagnosed by clinical follow-up. Conventional lung setting image of ¹⁸F-FDG PET/CT detected 40 of the 66 nodules and additional LD-HRCT detected 55 nodules. All 15 nodules missed by conventional lung setting imaging but detected by additional LD-HRCT were <1 cm in size. The sensitivity, specificity, and diagnostic accuracy of the modalities were 60.6 %, 85.2 %, and 71.1 % for conventional lung setting image and 83.3 %, 88.9 %, and 85.8 % for additional LD-HRCT. By ROC analysis, the area under the ROC curve (AUC) of conventional lung setting image and additional LD-HRCT were 0.712 and 0.827 respectively. Conclusion: Additional LD-HRCT with maximum inspiration was superior to conventional lung setting image of ¹⁸F-FDG PET/CT for the detection of metastatic lung nodules from colorectal cancer (P < 0.05).