Ionising radiation-free whole-body MRI versus 18F-fluorodeoxyglucose PET/CT scans for children and young adults with cancer: a prospective, non-randomised, single-centre study

Background Imaging tests are essential for staging of children with cancer. However, CT and radiotracer-based imaging procedures are associated with substantial exposure to ionising radiation and risk of secondary cancer development later in life. Our aim was to create a highly effective, clinically feasible, ionising radiation-free staging method based on whole-body diffusion-weighted MRI and the iron supplement ferumoxytol, used off-label as a contrast agent. Methods We compared whole-body diffusion-weighted MRI with standard clinical F-18-fluorodeoxyglucose (F-18-FDG) PET/CT scans in children and young adults with malignant lymphomas and sarcomas. Whole-body diffusion-weighted magnetic resonance images were generated by coregistration of colour-encoded ferumoxytol-enhanced whole-body diffusion-weighted MRI scans for tumour detection with ferumoxytol-enhanced T1-weighted MRI scans for anatomical orientation, similar to the concept of integrated F-18-FDG PET/CT scans. Tumour staging results were compared using Cohen's. statistics. Histopathology and follow-up imaging served as the standard of reference. Data was assessed in the per-protocol population. This study is registered with ClinicalTrials.gov, number NCT01542879. Findings 22 of 23 recruited patients were analysed because one patient discontinued before completion of the whole-body scan. Mean exposure to ionising radiation was 12.5 mSv (SD 4.1) for F-18-FDG PET/CT compared with zero for whole-body diffusion-weighted MRI. F-18-FDG PET/CT detected 163 of 174 malignant lesions at 1325 anatomical regions and whole-body diffusion-weighted MRI detected 158. Comparing 18F-FDG PET/CT to whole-body diffusion-weighted MRI, sensitivities were 93.7% (95% CI 89.0-96.8) versus 90.8% (85.5-94.7); specificities 97.7% (95% CI 96.7-98.5) versus 99.5% (98.9-99.8); and diagnostic accuracies 97.2% (93.6-99.4) versus 98.3% (97.4-99.2). Tumour staging results showed very good agreement between both imaging modalities with a. of 0.93 (0.81-1.00). No adverse events after administration of ferumoxytol were recorded. Interpretation Ferumoxytol-enhanced whole-body diffusion-weighted MRI could be an alternative to F-18-FDG PET/CT for staging of children and young adults with cancer that is free of ionising radiation. This new imaging test might help to prevent long-term side-effects from radiographic staging procedures.