Cancer Tracker

Surgical removal of a tissue sample is now the standard for diagnosing cancer. Such procedures, known as biopsies, are accurate but offer only a snapshot of the tumor at a single moment in time. Monitoring a tumor for weeks or months after the biopsy would be much more valuable, says Michael Cima, an MIT professor of materials science and engineering. He has developed the first implantable device that can do just that.

“What this does is basically take the lab and put it in the patient,” says Cima, who is also an investigator at the David H. Koch Institute for Integrative Cancer Research at MIT.

The device, which could be implanted at the time of a biopsy, would provide up-to-the-minute information about a tumor–whether it’s growing or shrinking, whether chemotherapy drugs have reached it, and whether it has metastasized or is about to do so. In a paper published in the journal Biosensors & Bioelectronics, Cima and his colleagues recently reported that their device successfully tracked for one month a chemical produced by human tumors growing in mice.

The cylindrical, five-­millimeter implant contains magnetic nanoparticles coated with antibodies specific to target molecules such as hormones produced by tumor cells. When target molecules enter the implant through a semipermeable membrane, they bind to the particles and cause them to clump together. Magnetic resonance imaging can detect the clumps–and track whether they’re getting bigger or smaller.

Implants that can test for pH levels, which reveal a tumor’s metabolism and its response to chemotherapy, could be commercially available in a few years, Cima says. These would be followed by devices that test for complex chemicals such as hormones and drugs.

Unlike biopsies, such technologies could alert doctors that the original tumor has started shedding cancer cells before those cells can form new tumors. “This is one of the tools we’re going to need if we’re going to turn cancer from a death sentence to a manageable disease,” Cima says.