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.
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.
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% of the time. If that person has a Cologuard test, there is a 42% chance that it will be positive because of the polyp. If the person has a FIT test, there is about a 22% chance it will be positive.
Another measure is how likely the test is to find cancers when they are present.
Colonoscopies find 95%. A one-time Cologuard test will be positive 94% of the time if a cancer is present, and a FIT test will be positive 74% 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% lower death rate from colon cancer than people who were not screened. The death rate fell to 2%, from 3%.
A 10-year European study of colonoscopy found a 30% reduction in the risk of getting colon cancer. It was 0.84% in a group that had colonoscopies and 1.22% 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.
The ultimate goal, though, is preventing colon cancer deaths. (Source: Freepik)
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.
What do the tests cost?
Many patients pay little or nothing because insurance, including Medicare, covers the tests. But testing does cost the health care system.
Prices for the testing vary, but one estimate says a colonoscopy for people with private insurance costs the insurer about $3,442. A single Cologuard test costs about $763, and a single FIT test costs about $91.
Why do doctors prefer colonoscopies?
Many doctors think they are saving patients’ lives with colonoscopies.
“The idea of finding and removing cancer precursor lesions became very attractive to physicians,” Lieberman said.
But there is also a financial incentive for the procedure.
“Colonoscopy is a massive revenue generator for hospital systems,” said Dr. Adewole Adamson, of the University of Texas at Austin, who studies cancer screening.
Doctors profit too, said Dr. Samir Gupta, a gastroenterologist at the University of California, San Diego. “When we do the procedure, that’s part of our income,” he said. “We are all conflicted.”
Many other countries with modern national health systems use FIT tests because they are cheap, and because they lack the capacity for wider use of colonoscopies.
But there are places in the U.S. that don’t emphasize colonoscopies. Most VA centers mail FIT tests to eligible patients every year.
So does Kaiser Permanente, one of the nation’s largest medical care providers. In the company’s lab in Northern California, for instance, testing is done “on an industrial scale,” said Dr. Theodore Levin, a Kaiser gastroenterologist, with 15,000 to 20,000 FIT tests processed each week.
In describing some of Kaiser’s motivation for offering FIT, Levin added, “All the physicians are salaried, so they are not doing screening to support their practice.”
Dr. Amitpal S. Johal, director of gastroenterology at Geisinger, a large health care system in Pennsylvania, says Cologuard is preferred because of its greater accuracy and because it only needs to be done every three years. The test is useful for the system’s large rural population for whom a center that does colonoscopies can be far away.
“Some of these people can’t drive five hours” for the test, he said, while “Cologuard will mail the test to them, and UPS will pick it up.”
When can I get a blood test instead of these options?
The Food and Drug Administration recently approved a blood test called Shield by the company Guardant Health. The test looks for fragments of DNA shed from colon cancers and polyps. If it finds evidence of cancer or large polyps, you need a colonoscopy.
The problem is that the test is not very accurate and does especially poorly at finding large polyps. Still, gastroenterologists say it is better than nothing.
The blood test also is expensive at $1,495. Medicare will pay for it every three years, Guardant said.
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. (Source: Freepik) 
The ultimate goal, though, is preventing colon cancer deaths. (Source: Freepik)
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