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

Summary 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 18 F-fluorodeoxyglucose ( 18 F-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 18 F-FDG PET/CT scans. Tumour staging results were compared using Cohen's κ 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 18 F-FDG PET/CT compared with zero for whole-body diffusion-weighted MRI. 18 F-FDG PET/CT detected 163 of 174 malignant lesions at 1325 anatomical regions and whole-body diffusion-weighted MRI detected 158. Comparing 18 F-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 κ 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 18 F-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. Funding Thrasher Research Fund and Clinical Health Research Institute at Stanford University.