New MRI technique could offer radiation-free option for pediatric cancer staging

A new whole-body MRI test that does not emit radiation could be an alternative to standard PET/CT imaging for cancer assessment in pediatric patients, according to a study published by The Lancet Oncology on Feb. 19.

Growing concern over ionizing radiation exposure in children undergoing 18F-fludeoxyglucose (18F-FDG) PET/CT imaging has led to the increased use of MRI for whole-body staging in this demographic.

“However, despite these recent advances, three major limitations have prevented the adoption of whole-body diffusion-weighted MRI for tumor staging in clinical practice,” wrote the study’s senior author, Heike E. Daldrup-Link, MD, of the Stanford University School of Medicine in California, and colleagues. These challenges include similar signals between the spleen and bone marrow during diffusion-weighted imaging, the short-term effect of contrast-agent enhancement, and limited background information.

The researchers strove to overcome these hindrances through the creation of a highly effective, clinically feasible, and ionizing radiation-free staging method based on whole-body diffusion-weighted MRI and the iron supplement ferumoxytol. Ferumoxytol, used in this study as an off label contrast agent, is comprised of ultrasmall superparamagnetic iron oxide particles that are detectable with MRI.

The study screened 22 children and young adults with malignant lymphomas and sarcomas using both whole-body MRI and 18F-FDG. Sensitivity (93.7 percent vs. 90.8 percent), specificity (97.7 percent vs. 99.5 percent), and diagnostic accuracy (97.2 percent vs. 98.3 percent) were found to be similar across the board for both screening techniques.

The average exposure to ionizing radiation was 12.5 mSv for 18F-FDG and was zero for whole-body MRI. No adverse reactions to the ferumoxtol were observed.

Not only does the new technique eradicate radiation exposure, but it is also cost-effective. The technique does not require specific equipment and can be easily used on different MRI scanners for about the same cost as an 18F-FDG exam.

“Present techniques used for diagnosis and treatment, albeit effective, might bear certain risks and thus do not meet our high standards on patient care. This new imaging test might solve this conundrum of the need for diagnostic cancer staging procedures and concurrent risk of secondary cancer development later in life,” concluded Daldrup-Link and colleagues.

In an associated commentary, Thomas C. Kwee, MD, of the University Medical Centre Utrecht in the Netherlands, wrote: “Although the technical feasibility and potential diagnostic value of using ultrasmall superparamagnetic iron oxide particles in a whole-body diffusion-weighted MRI protocol has been shown in these patients, further work is needed before it can become a clinical alternative to 18F-fludeoxyglucose.