Top Prospects in Colon Screening

Screening for colon cancer may soon involve swallowing a camera—a tiny one embedded in a pill-shaped capsule. One such device, the PillCam colon, recently became available to patients in Israel and Europe. As the 31-by-11-millimeter capsule passes through the digestive tract, it takes four images per second and beams them to a data recorder worn on the waist. Patients aren't exposed to radiation, as they are in virtual colonoscopy, but a laxative prep is required, same as with virtual and traditional colonoscopy. Last month, the Food and Drug Administration turned down the application by Given Imaging Ltd., the PillCam's Israeli manufacturer, to market the device in the United States, but the company is expected to try again when it has more data.

A blood test that can screen the colon is also in the works, and researchers at Johns Hopkins say it may become available in as little as two or three years. "I think we're going to use these tests like we use cholesterol [tests]," says Robert Getzenberg, a Hopkins cancer researcher who is investigating several proteins in the blood that serve as telltale signs of growths in the colon. Because the amount of one particular protein appears to correlate with the size of a polyp, patients with elevated levels could be monitored carefully, while those with the highest levels (indicating a more advanced growth) could be sent on for a colonoscopy. After analyzing samples from 236 volunteers, Getzenberg's group reported this month in Clinical Cancer Research a 97 percent success rate in correctly identifying patients with either cancer or an advanced precancerous growth.

Protein tests aren't the only game in town. Bert Vogelstein, another leading cancer researcher at Johns Hopkins, is investigating how DNA mutations that can also be identified in blood samples could become screening tools for colorectal cancer—and other malignancies.

While these experimental tests may soon make screening even simpler and more palatable, there's still only one way to remove a threatening polyp. And that requires the tried-and-true, albeit invasive, colonoscopy.