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Are there alternatives to colonoscopy?

Created date

September 16th, 2016
Cartoon image of a sick colon.

Cartoon image of a healthy colon.

Colorectal cancer is a collective term for cancers of the large bowel. This cancer is the second leading cancer killer in the United States and the third most common type for men and women. According to the U.S. Preventive Services Task Force (USPSTF), 134,000 persons will be diagnosed with the disease in 2016 and about 49,000 will die from it. 

The disease rarely produces symptoms in early stages. “Practically all colorectal cancers start as tiny polyps,” says Cynthia S. Rudert, M.D., F.A.C.P., a gastroenterologist in Atlanta, Ga., and medical advisor for the Celiac Disease Foundation. “Not all polyps are precancerous or cancerous, however.”

Who should get screened

“The USPSTF recommends screening from ages 50 to 75 for people with a normal risk for the disease,” says Andrew Kundrat, M.D., medical director at Riderwood, an Erickson Living community in Silver Spring, Md.. “For people 76 and up, it is an individual decision based on the patient’s health, prior history, and whether they have had prior screening.”

People at high risk for the disease, such as those with a family history, personal history, or inflammatory bowel disease, should talk to their doctor about when and how they should be screened. 

Screening options

Unlike many cancers, there are several screening tests that use different methods to detect colorectal cancer in the early stages. The USPSTF does not recommend one test over the other.

Colonoscopy

The entire colon is directly examined with a long flexible tube. If there are polyps, they can be removed at that time. Colonoscopies involve a bowel cleansing the day before and sedation during the procedure. 

Colonoscopy can detect over 90% of tumors and polyps, but screening rates remain low. “Only one out of three people who are eligible for a colonoscopy have one,” Rudert says. “Some people don’t want to go through the bowel preparation, others fear being sedated. Some people don’t want to lose a day of work.”

If you decide not to have a colonoscopy, you and your doctor can discuss which of the other screening tests may be best for your personal situation. “The doctor and the patient have a shared responsibility for colorectal cancer screening,” Kundrat says. “There should be a discussion about risks and benefits of each screening tool, and information about the patient’s current health and individual cancer risks. After the patient has all relevant information, they can make a decision, even if that decision is to forgo screening.”

Noninvasive options

Studies show that the majority of adults who are resistant to a colonoscopy will agree to one of the noninvasive screening methods: 

Virtual colonoscopy. Virtual colonoscopy is done via computerized tomography (CT) or magnetic resonance imaging (MRI). This test can detect polyps and tumors bigger than 6 millimeters. According to the National Institutes of Health (NIH), the test tends to detect insignificant lesions or benign structures outside of the colon between 40% and 70% of the time, which can lead to unnecessary treatment. Some insurances (including, as of this writing, Medicare) do not cover it. 

Fecal occult blood and fecal immunochemical blood tests. These tests look for blood in the stool. Fecal occult blood uses a chemical called guaiac to detect blood in the stool. Blood can also be present due to cancer or other reasons, such as inflammatory bowel disease. The fecal immunochemical blood test detects antibodies; thus, it is considered a more sensitive test. Both of these are recommended yearly and are done at home using a stick or brush to collect a sample. 

Stool DNA/FIT (Cologuard). This combination test, also done at home, detects abnormal DNA as well as red blood cells. “Stool DNA is a new technology,” Rudert says. “It looks for 11 DNA markers that can signal the presence of colorectal cancer. It can also detect precancerous polyps because they also shed cells with unique DNA markers.”

In a study published in the New England Journal of Medicine (which was supported in part by Exact Sciences, the manufacturer of Cologuard), this testing method detected 92% of cancers in a study sample of over 10,000. “In addition, the test was negative in 87% of patients without cancer or advanced precancerous lesions,” Rudert says.

According to the Cologuard website, false positives occur in 13% of people without cancer or precancerous lesions. “Researchers don’t yet know why,” Rudert says. “It may be that the tests are detecting abnormal cells before they become polyps or tumors.”

It is not yet known how often people should have this testing. “This is a new technology,” Rudert says. “Studies to collect longitudinal data are under way.”

A colonoscopy is highly recommended if you have a positive result on any of these noninvasive screening methods. 

Less common screening methods

A procedure called a sigmoidoscopy is similar to a colonoscopy but not as extensive. “Sigmoidoscopies are rarely recommended for screening,” Rudert says. “Only the lower third of the colon and the rectum are visualized; therefore, it can miss lesions farther up.”

Two screening tests not on the USPSTF list are double contrast barium (an enema) and methylated SEPT9 DNA (a blood test). There was not enough scientific evidence that showed they were effective in detecting cancer.

Your decision, your choice

Because of the public’s increased awareness of the life-saving importance of colon cancer screening, compliance with colorectal screening (all types) has risen from about 50% to 65% over a ten-year period.

“The overall message from the USPSTF is for people to get screened one way or the other because all of the tests can detect some cancers,” Kundrat says.

Thanks to better screening and treatments, the American Cancer Society reports there are more than one million survivors of colorectal cancer in America today.

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