A microchip that captures and stores images of rare cancer cells circulating in the blood may provide a way to monitor patients after surgery and could eventually guide treatment, U.S. researchers said in a study published on Wednesday.

Circulating tumor cells, or CTCs, shed from a tumor like seeds and can grow into new tumors. The presence of CTCs in the blood might tip off doctors that a cancer could spread to other parts of the body, the researchers said in the journal Science Translational Medicine.

CTCs might also help doctors quickly tell whether a patient is responding well to chemotherapy or other treatment, the article said.

"We're very interested in these cells because we believe these are the ones that are going to give us the most insight into cancer biology as well as cues to how cancer metastasizes," lead author Shannon Stott, of Massachusetts General Hospital and Harvard Medical School in Boston, said in a telephone interview.

With the help of a substance that works like a biological "glue," the microchip captures only the cells the researchers want to examine, Stott said. In this case it was the prostate specific antigen, which indicates the presence of prostate cancer. The device is coupled with a microscope which takes at least 6,000 images of the cells, Stott said.

"There's no preprocessing. You just draw the blood and stick it through the device," she said.

The hope is that the device will enable clinicians to learn more about tumors without having to cut into patients, Stott added.

"You could just do this blood test, so it's like a blood biopsy to get insight into the biological properties of the tumor," she said.

In the study, Stott and colleagues collected and, for the first time, counted circulating tumor cells from 55 cancer patients. The team monitored the cells before and after surgery.

"You can look at, not only the absolute number of CTCs that you have, but whether or not they have this ability to proliferate and divide," she said.

The team found that, in some patients, circulating tumor cells rapidly disappeared after surgery, while in others the cells persisted months afterward.

Researchers do not yet know whether the persistence or disappearance of the circulating tumor cells have a role in cancer recurrence, Stott said, stressing that this was an early pilot study.

"We're scaling up ... enrolling more patients to get a larger scale-critical study going to figure out what this means," she said.