TNM Staging of Non–Small Cell Lung Cancer: Comparison of PET/MR and PET/CT

RATIONALE: To compare the diagnostic accuracy of whole-body non-contrast-enhanced PET/MR with that of PET/CT in determining the stage of non-small-cell lung cancer. METHODS: This study was approved by the institutional review board and by national government authorities. Forty-two consecutive patients referred for the initial staging of non-small-cell lung cancer underwent whole-body imaging with a sequential trimodality PET/CT-MR system. PET/MR and PET/CT datasets were evaluated separately, and a tumor-node-metastasis (TNM) stage was assigned based on the image analysis. Nodal stations in the chest were identified according to the mapping system of the American Thoracic Society. The standard of reference was histopathology for the tumor stage in 20 subjects, for the nodal stage in 22 patients and for extrathoracic metastases in 5 subjects. All other lesions were confirmed by at least one different imaging method. Wilcoxon signed-ranks test was used for comparing PET/MR with PET/CT. RESULTS: PET/MR did not provide additional information compared with PET/CT. The diagnostic accuracy of both imaging modalities was equal (T staging: P = 0.177, N staging: P = 0.114, M staging: P = 0.465), however with advantages for PET/CT by trend. In the subgroup with histopathological confirmation of T stage and N stage, the situation was similar (T staging: P = 0.705, N staging: P = 0.334). CONCLUSION: This study indicates that PET/MR using a fast MR protocol does not improve the diagnostic accuracy of the staging of non-small-cell lung cancer.