Bottom Line: Newer tests are easier, quicker and can be just as effective…
Colonoscopy has generally been considered the gold standard for detecting and preventing colorectal cancer. But it’s not the only option.
What you may not realize: A handful of other tests—which are easier, cheaper and quicker—are now available and may encourage more people to actually get tested. What you need to know…
The American Cancer Society (ACS) and other major health groups have urged Americans to regularly undergo colonoscopy. And with good reason. Colonoscopy can detect more than 90% of cancers and precancerous polyps that are larger than about one-half inch.
The problem is, more than one-third of Americans who should be screened for colorectal cancer haven’t had screening—in part due to the onerous “prep” that includes fasting and drinking quarts of a foul-tasting liquid and often means spending hours on the toilet as your insides empty out.
New guidelines from the ACS advise patients with average risk for colon cancer (that is, no family history, genetic syndrome, inflammatory bowel disease or personal history of radiation to the abdomen or pelvic area to treat a prior cancer) to undergo regular screenings starting at age 45. Previously, screening started at age 50, but the age has been dropped to 45 because in recent years the percentage of colorectal cancer cases involving younger adults has risen. The recommended tests include colonoscopy, CT colonography and sigmoidoscopy (discussed later)—along with a number of high-sensitivity stool tests.
Colonoscopy is most effective at detecting precancerous polyps, but for people who won’t go for the procedure, stool-based tests (when performed regularly) can be almost as accurate as colonoscopy at detecting colorectal cancer.
Caveats: If you test positive on one of these tests, you’ll still need to follow up with colonoscopy. And the tests must be repeated every one to five years, depending on the test. Colonoscopy is typically undergone every 10 years (more frequently if polyps are detected). Other tests to discuss with your doctor…
• Guaiac fecal occult blood test (gFOBT). This test uses a chemical (guaiac) to detect a blood component in stools. The presence of blood is a common sign of cancer. The test can detect 60% to 80% of colon cancers, though it is even more accurate if done every year, as recommended.
However, all stool tests, including gFOBT, are more likely than colonoscopy to miss precancerous polyps, which are less likely to bleed than cancer. This is why gFOBT should be repeated yearly—to catch the polyps that have turned into early-stage cancer and begun to bleed.
What it involves: You use an applicator stick to smear a bit of stool on a test card. You repeat this on two or three consecutive days, then return the cards to your doctor (or mail to a testing laboratory).
Pros: gFOBT only requires a stool “smear.” The test usually costs $25 or less and is covered by insurance.
Cons: You must collect several smears…give up red meat for several days because the test can’t differentiate dietary animal blood from human blood…and temporarily quit taking medications, such as aspirin or ibuprofen (Motrin), that can cause intestinal bleeding.
• Fecal immunochemical test (FIT). A more recent variation of the gFOBT, FIT uses an antibody to detect blood hemoglobin in a stool sample. It’s about 80% effective at detecting cancers, though is even more accurate when repeated yearly, as recommended.
What it involves: Test kits vary by manufacturer, so read directions carefully. Typically, you stick a long-handled brush into a stool sample…transfer the sample to a special collection card…and mail it to a testing laboratory. The cost is about the same or slightly more than the gFOBT, and it’s covered by insurance.
Pros: You only need a single stool sample…there are no dietary restrictions…and the test only detects human hemoglobin from the lower digestive tract, which reduces false readings from dietary sources and noncancerous causes of stomach/upper-intestinal bleeding.
Cons: Like gFOBT, the test usually misses precancerous polyps. Still, due to FIT’s improved accuracy and convenience, most experts consider it to be a better test than gFOBT, but the latter remains available based on its low cost and track record of detecting cancers.
• Cologuard. This is the newest screening test. It combines blood-stool detection with the ability to detect DNA mutations often associated with colorectal cancers. Overall, Cologuard can detect about 92% of cancers—better than gFOBT and FIT. It also can detect more than 40% of “advanced” polyps (larger or with more precancerous features) compared with about 25% for FIT. The test is expensive—about $650, though it is covered by Medicare and most insurers.
What it involves: A small container is placed under the toilet seat to collect a complete stool, which is then sent to a testing laboratory.
Pros: Cologuard is done at three-year intervals rather than every year. It doesn’t require preparation or dietary restrictions.
Cons: It has more false positives (about 13%) than other tests, which lead to more unnecessary follow-up colonoscopies.
• Flexible sigmoidoscopy. Like colonoscopy, it utilizes a flexible, camera-tipped tube to examine the lower part of the colon (the sigmoid colon) and the rectum. Repeated every five years, it provides some of the same benefits as colonoscopy but doesn’t require sedation. Most insurers cover it.
The downsides: Sigmoidoscopy won’t detect polyps/cancers in the upper half of the colon. Also, the lack of sedation, while considered safer, means the procedure is more uncomfortable than colonoscopy.
• CT colonography, also known as virtual colonoscopy, is an imaging test that is comparable to colonoscopy at detecting advanced adenomas and cancers. It is noninvasive, and sedation isn’t required.
However, CT colonography requires a bowel prep, and you must drink a contrast dye. Medicare and many private insurers do not cover CT colonography. CT scans produce radiation exposure, but newer technology has lowered the amount of radiation considerably.
