A magnetic wire used to snag scarce and hard-to-capture tumor cells could prove to be a swift and effective tactic for early cancer detection, according to a study by researchers at the Stanford University School of Medicine.

The wire, which is threaded into a vein, attracts special magnetic nanoparticles engineered to glom onto tumor cells that may be roaming the bloodstream if you have a tumor somewhere in your body.

With these tumor cells essentially magnetized, the wire can lure the cells out of the free-flowing bloodstream using the same force that holds family photos to your refrigerator.

The technique, which has only been used in pigs so far, attracts from 10-80 times more tumor cells than current blood-based cancer-detection methods, making it a potent tool to catch the disease earlier.

The technique could even help doctors evaluate a patient's response to particular cancer treatments: If the therapy is working, tumor-cell levels in the blood should rise as the cells die and break away from the tumor, and then fall as the tumor shrinks.

For now, Sam Gambhir, MD, professor, and chair of radiology and director of the Canary Center at Stanford for Cancer Early Detection, is focused on the wire as a cancer-detection method, but its reach could be much broader.

"It could be useful in any other disease in which there are cells or molecules of interest in the blood," said Gambhir, who developed the wire with the help of his colleagues.

"For example, let us say you are checking for a bacterial infection, circulating tumor DNA or rare cells that are responsible for inflammation in any of these scenarios, the wire and nanoparticles help to enrich the signal, and therefore detect the disease or infection," said Gambhir.

The study will be published online July 16 in Nature Biomedical Engineering. Gambhir is the senior author. Postdoctoral scholar Ophir Vermesh, MD; surgery resident Tianjia Jessie Ge, MD; and MD-Ph.D. student Amin Aalipour share lead authorship.

No vial of blood necessary

Cells that have sloughed off the tumor and cruise the bloodstream freely, otherwise known as circulating tumor cells, can serve as cancer biomarkers, signaling the presence of the disease.

"These circulating tumor cells are so few that if you just take a regular blood sample, those test tubes likely would not even have a single circulating tumor cell in them," said Gambhir, the Virginia and D.K. Ludwig Professor of Clinical Investigation in Cancer Research.

It would be like searching for a grain of sand in a bathtub, but only scooping out a few cups of water. "We estimate that it would take about 80 tubes of blood to match what the wire can sample in 20 minutes," Gambhir said.

Of course, he continued, it is not practical to remove 80 test tubes of blood from one person; that is more than a half-liter. "So, we are hoping this approach will enrich our detection capability and give us better insight into just how rare these circulating tumor cells are, and how early on they exist once the cancer is present."