Impact of FDG-PET and Dynamic Contrast-Enhanced MRI in Comparison with DWI for N-Staging in Lung Cancer Patients

Background: Regarding mediastinal N-staging in lung cancer patients, computed tomography (CT), magnetic resonance imaging (MRI), and integrated (18)Fluorine-fluorodeoxyglucose-positron emission tomography/CT (F-18-FDG-PET/CT) are the most widespread imaging methodologies in clinical routine. Objectives: In order to further extract information from non-invasive staging, we evaluated the use of F-18-FDG-PET/CT and dynamic contrast enhanced (DCE) and diffusion-weighted imaging (DWI) MRI using histopathology as the diagnostic gold standard. Patients and Methods: A total number of 50 patients had undergone MRI of the chest within two weeks prior to surgery for histopathological proof. DCE-MRI was evaluated on the basis of region of interest (ROI)-based signal intensity/time (SI(T) curves in the respective mediastinal lymph nodes (LNs). In total, 28 LNs could be allocated to the corresponding histopathological findings, as well as to corresponding findings in F-18-FDG-PET/CT. Results: Malignant LNs presented with significantly higher FDG uptake in PET. Significant differences between malignant and benign LNs were found for DCE-MRI regarding the parameters MaxE, 4-minutes value, SE, EP and EP/MaxE. In DWI-MRI, malignant LNs presented with significantly lower signal intensity compared to benign LNs (p < 0.01). An apparent diffusion coefficient (ADC) threshold of 1528 mm(2)/s was found to exclude malignancy for LNs that are above the threshold. Conclusion: F-18-FDG-PET in addition with MRI that includes DWI might improve mediastinal N-staging, which is of interest in cases of FDG-equivocal LNs. An ADC threshold of 1528 mm(2)/s might potentially help to further classify LNs with indefinite PET-findings. DCE-MRI of mediastinal LNs seems not yet to be approved for clinical routine.