Most medical experts consider colonoscopy the best colorectal cancer screening option. Studies show it to be the most effective way to detect cancer or polyps that may lead to cancer. Because gastroenterologists can remove suspicious findings at the time of screening, colonoscopy performed correctly can prevent cancer.
But, not everyone who should have a colonoscopy gets one. “Many people put off a colonoscopy because the test is bothersome, requiring time off from work and what is viewed as an unpleasant bowel prep,” says Lawrence R. Schiller, M.D., director of gastroenterology at Baylor University Medical Center at Dallas. “Also, patients are usually sedated during the exam and will need a companion to see them home afterward.”
Nearly one in three adults ages 50 to 75 hasn’t undergone the recommended colorectal cancer screening. To increase screening rates and save more lives, the United States Preventive Services Task Force (USPSTF), a federal panel of medical experts, has emphasized several noninvasive options to encourage more people to be tested. Even though these tests—outlined in the June 2016 issue of the Journal of the American Medical Association—may be less effective than colonoscopy, the USPSTF feels that the best screening test is the one that gets done.
But you’ll have to undergo a colonoscopy to look for polyps or cancer if abnormalities are detected with a less invasive test.
The USPSTF still recommends screening for all individuals ages 50 to 75 who are at average risk for colorectal cancer and who have no symptoms.
The task force doesn’t recommend routine screening for people ages 76 to 85 but says older patients should decide with their doctors whether screening may be beneficial. Screening in people older than 85 is not recommended.
The decision is typically based on three factors: whether the patient is healthy enough to sustain cancer treatment, has a life-limiting condition, or has been screened before.
An expanded choice of tests
The USPSTF suggests that these screenings be used to detect colorectal cancer:
• Colonoscopy (every 10 years). Colonoscopy, which remains the gold standard for colorectal cancer screening, involves inserting a flexible tube with a camera through the anus and rectum and advancing it through the entire colon. Risks include the possibility of perforation, bleeding, infection, or complications associated with sedation.
• Flexible sigmoidoscopy (every five years). A short, flexible tube is used to inspect only your rectum and lower portion of the colon. No sedation is used, but some bowel prep is required. It has the same rare bleeding and perforation risks as colonoscopy but to a lesser extent.
The test can be combined with a stool-based fecal immunochemical test (FIT), reducing frequency to every 10 years, but the stool test is required annually; experts say that this combined method is likely more accurate and dependable than either method alone.
• Stool-based tests (every one to three years). One of three tests may be used: a high-sensitivity guaiac-based fecal occult blood test (hsFOBT), a FIT, or a stool DNA test. Each involves testing the stool—which you collect at home using a provided kit and then submit to your doctor or a lab—for the presence of blood.
The USPSTF doesn’t recommend any single test, but the DNA test, sold on the market as Cologuard, has more false-positives than the other tests and may lead to unnecessary follow-up colonoscopy. The hsFOB, when performed annually, is believed to be just as effective as screening colonoscopy done every 10 years as long as colonoscopy is used to check those with positive tests.
• Computed tomography (CT) colonography (every five years). Also called a virtual colonoscopy, this noninvasive test uses two- and three-dimensional images of the colon and rectum to look for abnormalities.
However, a small tube is inserted into the colon to infuse gas to distend the colon before you’re moved through the scanner. Although you don’t have to be sedated for the test, bowel prep is required. The test also exposes you to radiation.
• Epi proColon. Though not on the list of the USPSTF’s recommended colorectal cancer screening tests, the Epi proColon, approved by the U.S. Food and Drug Administration in April 2016, is a blood serum test that can detect abnormal DNA associated with colorectal cancer.
According to the USPSTF, the test detects signs of cancer only slightly more than half the time (like flipping a coin), which means that if your test results come back negative (no evidence of cancer), it doesn’t ensure that you’re colorectal-cancer free. The Epi proColon is not meant to be a primary screening tool; instead, doctors may suggest it as a “last resort” test to patients who refuse to undergo other screenings.
One test you’ll no longer see on the updated list of approved tests is the double-contrast barium enema, because newer tests have surpassed its sensitivity and reliability.
Which test is best?
The USPSTF doesn’t recommend one test over another for colorectal cancer screening, but implies that the tests with the best balance of benefits and harms are colonoscopy, CT colonography, FIT and combined FIT, and flexible sigmoidoscopy.
Factor in cost, too: Not all health insurers cover CT colonography, for example, and some may not consider follow-up colonoscopies for positive noninvasive tests to be screening tests, so they may cost more.
“Providers tend to focus on colonoscopy and may not mention other options,” Schiller says. “For patients who refuse colonoscopy, certain noninvasive screening exams are a reasonable alternative when performed at the proper intervals.”
Ultimately, the best test for you is the one you’re willing to undergo and repeat.
A new blood-based test
Though not on the list of the USPSTF’s recommended colorectal cancer screening tests, the Epi proColon, approved by the U.S. Food and Drug Administration in April 2016, is a blood serum test that can detect abnormal DNA associated with colorectal cancer.
According to the USPSTF, the test detects signs of cancer only slightly more than half the time (like flipping a coin), which means that if your test results come back negative (no evidence of cancer), it doesn’t ensure that you’re colorectal-cancer free.
The Epi proColon is not meant to be a primary screening tool; instead, doctors may suggest it as a “last-resort” test to patients who refuse to undergo other screenings.
This article was first published on Sept. 16, 2016, but has been updated.