Colon cancer screening saves lives. If you are 50 years or older, you need to be screened (or earlier if you have a family history). But what test should you choose? The good news is that you have several options for colon cancer screening. The bad news is that they aren’t all equivalent, and choosing the best test can be confusing. The most recent US Preventive Services Task Force recommendations endorsed the following screening options, but left it to patients and medical providers to decide which is best. Here’s a synopsis to help inform that decision:
- The gold standard (I’m biased, but you can’t top the accuracy of a colonoscopy)
- Sensitivity > 95%*
- Specificity > 95%*
- The only screening test that is also preventive. This is key. By removing polyps, we can prevent future cancers.
- Average national cost: $1390
- Frequency: every 10 years, if negative
- Time commitment: 1 day
- Risks: colonoscopy is invasive, and there is a potential, though rare, risk of bleeding and/or bowel injury.
*Sensitivity refers to the percentage of patients with colon cancer who have a positive test. Specificity refers to the percentage of patients without colon cancer who have a negative test.
Fecal Immunochemical Test (FIT)
- An annual, non-invasive test for hidden blood in the stool.
- Method: performed by you at home by brushing the surface of a bowel movement with a small paintbrush, and applying to a test card.
- Purely screening, not preventive.
- MUST be performed every year to be effective.
- Sensitivity = 73%
- Specificity = 96%
- Average cost = $19
- Time commitment: minutes
- Risks: no direct risks, aside from potential missed colon cancer
FIT-DNA (aka Cologuard®)
- The newest non-invasive stool test. Results are primarily driven by a FIT component, but the test also identifies DNA mutations that can be a sign of cancer.
- Method: the company ships a collection container to your home. You have a full bowel movement in the container and ship it back.
- Sensitivity = 93%
- Specificity = 89%
- Average cost = $650
- Time commitment: about an hour
- Frequency: Currently unknown. The Cologuard company proposes every 3 years, but this is not guided by evidence. The FDA has asked for further data to determine the optimal frequency.
CT Colonography (aka Virtual Colonoscopy)
Though initially promising, this test has become largely irrelevant. It involves cleaning your bowels out as you would for a colonoscopy, then undergoing a specialized CT scan (after your colon is inflated with air). The overall inconvenience, cost, need to follow positive tests with a real colonoscopy, and inferiority to standard colonoscopy have made this a niche player.
Flexible sigmoidoscopy + annual FIT testing
Not a common choice. A sigmoidoscopy is like a colonoscopy (same prep, same sedation) but only evaluates the left side of the colon. This is rarely ever used, because a colonoscopy only takes a few more minutes and can evaluate the whole colon.
All of the above are effective, and reasonable, options. All are better than nothing. I can’t emphasize that enough. Colon cancer is preventable. So take your pick. The 2 “best” options are probably colonoscopy and FIT testing. Colonoscopy is the most effective, least frequent, and is preventive, but is expensive and has some risks (note: the “expense” is covered by all insurance plans). FIT testing is the cheapest, and is pretty good at detecting cancer, but cannot identify polyps. It also has to be performed every year, which can be difficult to commit to. Cologuard is advertising heavily on TV. You’ve probably seen the ads. I would be careful with this one. It is very expensive, and isn’t much better than a cheap FIT test (which it actually utilizes). It also has a higher false-positive rate and the optimal frequency is unknown.
There are currently ongoing prospective, randomized controlled studies comparing colonoscopy to FIT testing (including a large study in the Veterans Administration system), but the results will take more than a decade. For now, if you are uncertain, speak with your primary care physician, or make an appointment to talk directly with a provider in one of our offices.
-Christopher McGowan, MD, MSCR