A modified MRI technique can effectively detect tumors in young cancer patients without exposing them to radiation, according to a small study published in The Lancet Oncology.
The method, called whole-body diffusion-weighted MRI, employs a contrast agent consisting of iron oxide nanoparticles.
This technique proved roughly as effective as 18F-FDG-PET/CT scans for detecting lymphoma and sarcoma in pediatric and young adult patients.
Researchers also noted that, as the MRI technique does not employ ionizing radiation, it might help prevent some of the adverse effects typically observed in patients who have undergone radiographic staging, particularly, secondary malignancies.
“I’m excited about having an imaging test for cancer patients that requires zero radiation exposure,” said senior study author Heike Daldrup-Link, MD, of the Stanford University School of Medicine in California.
She and her colleagues pointed out that, in the past, certain obstacles prevented physicians from using whole-body MRIs. For one, the scans take up to 2 hours, whereas a whole-body PET/CT takes only a few minutes.
In addition, in many organs, MRI does not distinguish healthy tissue from cancerous tissue. And existing contrast agents leave the tissues too quickly to be used in a lengthy, whole-body MRI.
In an attempt to overcome these obstacles, Dr Daldrup-Link and her colleagues used a contrast agent consisting of ferumoxytol nanoparticles. Injections of these iron oxide nanoparticles are approved by the US Food and Drug Administration (FDA) to treat anemia, and the researchers obtained FDA permission for use in their study.
The nanoparticles are retained in the body for days. On MRIs, they cause blood vessels to appear brighter, providing anatomic landmarks. The nanoparticles also cause healthy bone marrow, lymph nodes, livers, and spleens to appear darker, which makes tumors stand out.
The researchers compared the whole-body diffusion-weighted MRI method to PET/CTs in 22 patients, ages 8 to 33, who had lymphoma or sarcoma. Fourteen of the patients had Hodgkin lymphoma, 5 had non-Hodgkin lymphoma, 1 had Burkitt leukemia, 1 had Ewing’s sarcoma, and 1 had osteosarcoma.
The team found the MRI scans and PET/CT scans provided comparable information, although tumor detection was slightly better with PET/CT. The PET/CTs detected 163 of the 174 total tumors, and the MRIs detected 158.
The two methods had similar levels of sensitivity, specificity, and diagnostic accuracy. Sensitivity was 93.7% with PET/CT and 90.8% with MRI. Specificity was 97.7% with PET/CT and 99.5% with MRI. And diagnostic accuracy was 97.2% with PET/CT and 98.3% with MRI.
The researchers also noted that none of the patients experienced adverse reactions to the ferumoxytol nanoparticles, although the FDA previously observed a small risk of allergic reaction to the nanoparticles’ coating.
Dr Daldrup-Link said future research will aim to validate the MRI method in larger, more diverse groups of cancer patients, as well as examine its possible use for monitoring tumors over the course of cancer treatment. The technique also holds promise for scanning patients after their treatment is complete.
