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Ferumoxytol-enhanced whole-body diffusion-weighted MRI can be an alternative to 18F-FDG PET/CT for staging of children and young adults with cancer

Imaging tests are essential for staging of children with cancer. However, computed tomography ( CT ) and radiotracer-based imaging procedures are associated with substantial exposure to ionising radiation and risk of secondary cancer development later in life.

The aim of the study 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.

Researchers have compared whole-body diffusion-weighted MRI with standard clinical 18F-Fluorodeoxyglucose ( 18F-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 18F-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.

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 for 18F-FDG PET/CT compared with zero for whole-body diffusion-weighted MRI.

18F-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% versus 90.8%; specificities 97.7% versus 99.5%; and diagnostic accuracies 97.2% versus 98•3%.

Tumour staging results showed very good agreement between both imaging modalities with a κ of 0.93.

No adverse events after administration of Ferumoxytol were recorded.

In conclusion, Ferumoxytol-enhanced whole-body diffusion-weighted MRI could be an alternative to 18F-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. ( Xagena )

Klenk C et al, The Lancet Oncology 2014; 15: 275-285