New colon cancer test promising
Johns Hopkins University researchers are developing a simple blood test that can help doctors determine who needs a colonoscopy, a screening procedure for colon cancer recommended for all adults older than 50 -- but one considered so unpleasant that many avoid it.
The new test, which looks for cancer-related proteins in the blood, identifies colon cancer and precancerous polyps almost as well as a colonoscopy, according to a study published in the journal Cancer Research.
The authors say their test won’t replace colonoscopies but might provide a noninvasive means of identifying high-risk patients -- and an incentive for them to undergo the more invasive procedure.
“Part of what we are trying to do here is use blood markers for cancer like we do cholesterol levels to predict heart disease risk,” said Robert H. Getzenberg, a cancer researcher at the Johns Hopkins University School of Medicine and lead author of the paper. “If I could tell you [that] you have a 92% chance of having colon cancer, you might be more willing to undergo a colonoscopy.”
The blood test might also reduce the overall number of people who need a colonoscopy by screening out low-risk patients. “Someone at high risk should have the test right away, while someone who tests negative may not need to be looked at for another year,” Getzenberg said.
As the U.S. population ages and more people need screening, he added, the number of patients will probably outpace the number of doctors available to perform colonoscopies. A blood screening could reduce demand, experts said -- if the test proves valid in larger studies and receives federal approval.
This year in the U.S., about 150,000 people will be diagnosed with colorectal cancer and 52,000 people will die of it, according to the National Cancer Institute.
Doctors use several tools to screen for colon cancer and precancerous lesions, including blood tests and imaging technologies such as X-rays and CT scans (known as “virtual” colonoscopies). Another promising new test identifies genetic markers for cancer in stool samples.
A traditional colonoscopy, however, is considered the most accurate test. The American Cancer Society recommends that patients undergo at least one colonoscopy every 10 years, beginning at age 50. African Americans and people with a family history of colorectal cancer should begin screening earlier, experts say.
The procedure requires fasting, consumption of powerful laxatives, anesthesia and the insertion of a optical scope in the rectum. It also carries the risk of a punctured colon.
