New Cancer Screening Reduces Radiation Risk

Traditional full body cancer screening exposes patients to high levels of radiation. Recently, researchers have developed a method for scanning patients for cancer tumors without exposing them to radiation. This is especially significant for young cancer patients, who are vulnerable to developing secondary cancers later in life from early radiation exposures.

Researchers at the Stanford University School of Medicine and Lucile Packard Children's Hospital Stanford developed the new method, described in The Lancet Oncology. They modified magnetic resonance imaging (MRI) to employ a novel contrast agent to find tumors. The new MRI-based method is as effective as scans that use ionizing radiation, according to a press release announcing the findings.

The currently used whole-body PET-CT technology is effective at cancer detection but a single scan can expose patients to "as much radiation as 700 chest X-rays." For children and teenagers, who are still growing, these exposures are especially dangerous.

"I'm excited about having an imaging test for cancer patients that requires zero radiation exposure," said senior author Dr. Heike Daldrup-Link, associate professor of radiology at Stanford and a diagnostic radiologist at the hospital. "That is a big deal."

To develop their method, the team compared their modified MRI technique to the standard PET-CTs in 22 patients ages 8 to 22 who had lymphoma or sarcoma.

In the past, whole-body MRI scans, which the team modified for their method, took up to two hours to complete and could not differentiate between healthy and cancerous tissues in many organs. The whole-body PET-CT takes only a few minute and is effective at tissue differentiation, making it the go-to scan for cancer detection.

To modify the MRI scan to make it more effective, the Stanford team used a new contrast agent consisting of nanoparticles of iron. Injections of iron nanoparticles are used on patients to treat anemia and are approved by the FDA. The particles cause healthy bone marrow, lymph nodes, liver and spleen cells to appear darker, which helps tumors stand out.

When comparing the PET-CTs to the adjusted MRI scans, the researchers found that the PET-CTs detected 163 of 174 total tumors in 22 patients while the MRIs found 158 of 174 tumors. "The two methods had similar levels of sensitivity, specificity and diagnostic accuracy," according to the release.

"We were able to find a new way to integrate anatomical and physiological MRI information and make it more efficient," said Dr. Christopher Klenk, a postdoctoral scholar and the paper's lead author.