Ferumoxytol-enhanced MRA is safe for chronic kidney disease patients

Ferumoxytol-enhanced MR angiography (MRA) appears to be safe for chronic kidney disease (CKD) patients, researchers have reported.

The findings suggest a promising alternative MRA contrast agent for patients with CKD, who are vulnerable to nephrotoxicity, wrote a team led by Perry Hampilos, MD, of Massachusetts General Hospital in Boston. The group's results were published January 27 in the International Journal of Cardiovascular Imaging.

"Even though magnetic resonance angiography can be performed without contrast, there are limitations in image quality related to artifact and sequence time," the team explained. "Hence an alternative contrast agent is needed for vascular imaging in this select subgroup."

Use of conventional contrast agents in CT and MR imaging can be hindered in patients with CKD due to potential damage to the kidneys, the authors explained. Ferumoxytol is an iron-based compound originally developed as an intravascular contrast agent for MR imaging -- and could be a good alternative for this population.

"The ultrasmall superparamagnetic iron oxide particle demonstrates T1, T2, and T2* shortening of relaxation times, yielding a strong signal in MR imaging similar to gadolinium-based contrast agents," the researchers wrote.

Hampilos and colleagues reviewed 24 MRA exams of the chest, abdomen, and pelvis performed on CKD patients. All study participants were considered suitable for ferumoxytol administration; each received a dose of 4 mg/kg of the agent and was monitored postinjection.

Three observers assessed the quality of the ascending, descending, suprarenal, and infrarenal aortic segments using a four-point scoring system (nondiagnostic, poor vascular definition, good vascular definition, and excellent vascular definition). The investigators also performed quantitative analyses that included assessment of signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and heterogeneity index.

None of the patients had adverse reactions to the ferumoxytol, the group noted. It reported the following:

• Of 72 vascular segments evaluated using ferumoxytol with MRI, 90.8% of the images were rated as having excellent vascular definition, and 9.2% were rated as having good vascular definition.
• Interobserver agreement was substantial (kappa = 0.647), and there were no statistically significant differences in ratings between observers.

"Our … review of 24 cases showed primarily excellent imaging quality with adequate SNR and CNR and low heterogeneity index," the investigators wrote.

The team noted that ferumoxytol is underused for this indication, perhaps due to a combination of cost, physician resistance to off-label use, and safety concerns regarding a prior black box warning from the U.S. Food and Drug Administration (FDA) regarding severe reactions.

But these study findings add to "the growing literature showing a strong efficacy and safety profile at doses well below iron repletion dosing that triggered the warning," they concluded, adding that "institutions should develop imaging protocols and provide information to referring clinicians to facilitate contrast-enhanced imaging of vascular anatomy and pathology in selected patient populations."

The complete work can be accessed here.