Team Metabolic Health
Doctors can provide alternative forms of screening for colon and rectal cancer but sometimes have a good reason to stick with the colonoscope.
This year about 53,000 Americans are expected to die from colon or rectal cancer. Doctors say most people should start getting screened at age 45. Yet many who are eligible skip testing.
When most people in this country think of colon cancer screening, they think of colonoscopies, which let doctors examine the colon but can be inconvenient. Yet there are other equally acceptable options for screening.
If more people knew about other kinds of colorectal cancer testing, some experts hope, perhaps some who put off colonoscopies would be screened and deaths from colon cancer could be avoided.
A colonoscopy will find 95 percent of the time if cancer is present, but other tests that rely on fecal samples are not always as accurate .Credit: iStock/Getty Images Plus
Here’s what you need to know about colonoscopies and fecal tests, which to ask for, and why your doctor might be recommending one over the other.
How do colonoscopies and fecal tests work?
Colonoscopies are widely used, but there is another option available: fecal tests.
Both types of test attempt to find cancers and large polyps — growths on the wall of the colon — that occasionally turn into cancers. Cancers that are found early often can be cured when doctors simply cut them out. Finding and removing polyps can also prevent cancers.
Colonoscopies start with a patient’s taking strong laxatives to empty the colon. On the day of the test, the patient is sedated. Then, a doctor inserts a colonoscope — a flexible tube with a video camera at the end — into the rectum and colon and looks for polyps and cancers to remove. The doctor may also take samples for study in a lab.
If no polyps or cancers are found, the average patient can wait 10 years before having another colonoscopy.
Fecal tests can be done at home. Patients collect a stool sample and mail it to or drop it off at a testing lab.
One option is the fecal immunochemical test, or FIT, which should be repeated annually. A lab analyzes the sample for traces of blood, which can indicate a polyp or cancer. Large polyps and colon cancers sporadically ooze small amounts of blood. If blood is detected, the patient must have a colonoscopy.
Another more complex fecal test is Cologuard, repeated every three years. It looks for blood in stool and also for abnormal DNA from large polyps and colon cancers. Like the FIT test, Cologuard must be followed by a colonoscopy if blood or abnormal DNA are present.
Which option actually works better?
That depends on what is meant by “better.”
One measure is how often a test finds large polyps.
If a person who has a large polyp has a colonoscopy, the test will detect it 95 percent of the time. If that person has a Cologuard test, there is a 42 percent chance that it will be positive because of the polyp. If the person has a FIT test, there is about a 22 percent chance it will be positive.
Another measure is how likely the test is to find cancers when they are present.
Colonoscopies find 95 percent. A one-time Cologuard test will be positive 94 percent of the time if a cancer is present, and a FIT test will be positive 74 percent of the time.
The ultimate goal, though, is preventing colon cancer deaths. For now, no one really knows which test performs better. One large clinical trial by the Department of Veterans Affairs is comparing the number of colon cancer deaths among 50,000 patients randomly assigned to have a colonoscopy or an annual FIT test and followed for 10 years.
Results are expected in 2027 or 2028.
While those studies are continuing, other studies have compared a screening test with no test.
One study found that after 30 years, people who had fecal tests had a 33 percent lower death rate from colon cancer than people who were not screened. The death rate fell to 2 percent, from 3 percent.
A 10-year European study of colonoscopy found a 30 percent reduction in the risk of getting colon cancer. It was 0.84 percent in a group that had colonoscopies and 1.22 percent in a group that was not screened. There was no difference in the risk of dying from colon cancer.
Whether the reduction in the risk of getting colon cancer is worth a potential risk of injury during the surgery is “in the eye of the beholder,” said Dr. Michael Bretthauer, a gastroenterologist at the University of Oslo who led the study.
Can I ask my doctor for a fecal test if I prefer it to a colonoscopy?
Of course — if you are of average risk, meaning no family history of colon cancer and no genetic condition that predisposes to colon cancer. If you are at a higher risk, your doctor is likely to advise a colonoscopy.
When patients of average risk ask Dr. David Lieberman, a gastroenterologist at Oregon Health and Science University, if they can skip the colonoscopy, he explains that a fecal test and a colonoscopy accomplish different things. Fecal tests are likely to find cancers when they are early enough to be cured. But he says those tests are not so good at finding precancerous polyps. While the hope is that, repeated over time, the fecal tests will find polyps, colonoscopies find both with a single test.
Hearing that, he said, most patients decide they want colonoscopies.
Credit: The New York Times