Fast, gadolinium-free whole-body cancer imaging proves feasible for young patients

Stanford researchers have developed a PET/MRI system for whole-body staging of solid tumors in young people that uses an iron supplement rather than a gadolinium-based MRI contrast agent and yields accurate results in less than an hour.

Molecular Imaging and Biology published the team’s report online July 18.

In the prospective trial testing the “Stanford approach,” Anne Muehe, MD, of Lucile Packard Children’s Hospital and colleagues imaged 20 patients with solid tumors on a 3T PET/MRI scanner following intravenous injection of standard fluorodeoxyglucose (¹⁸FDG) and, off label, the iron supplement ferumoxytol.

The patients ranged in age from 11 to 30.

The researchers compared time needed for patient preparation, PET/MRI image acquisition and data processing before (n = 5) and after (n = 15) time-saving interventions they developed.

Then they compared the ferumoxytol-enhanced PET/MRI images with clinical standard staging tests on radiation exposure and tumor staging results.

“Tailored workflows significantly reduced scan times from 36 to 24 minutes for head to mid-thigh scans,” the authors report, adding that the obtained their streamlined PET/MRI scans with significantly reduced radiation exposure: mean 3.4 millisieverts vs. 13.1 millisieverts in PET/CT with diagnostic CT.

The ferumoxytol-enhanced PET/MR scans provided equal or superior tumor staging results compared to clinical standard tests in 17 out of 20 patients, Muehe and colleagues write.

Compared to PET/CT, the Stanford-approach PET/MR technique had comparable detection rates for pulmonary nodules with diameters of equal or greater than 5 millimeters (94 vs. 100 percent). However, the technique detected significantly fewer nodules with diameters of less than 5 millimeters (20 vs. 100 percent).

FDG-avid nodules (those that took up the FDG, signaling cancer) were detected with slightly higher sensitivity on the PET of the PET/MRI compared to the PET of the PET/CT (59 vs. 49 percent).

Noting that the experimental technique’s detection of small pulmonary nodules with PET/MR needs to be improved, the authors underscore that using the iron supplement ferumoxytol “off label” as an MRI contrast agent avoided gadolinium chelate administration.

“Our streamlined ferumoxytol-enhanced PET/MR protocol provided cancer staging of children and young adults in less than one hour with equivalent or superior clinical information compared to clinical standard staging tests,” they write.