March is Colorectal Cancer Awareness Month
There are several screening tools for colon cancer: colonoscopy, fecal occult blood test (FOBT), fecal immunochemical test (FIT), and the new kid on the block, Cologuard.
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Like FOBT and FIT, Cologuard uses a stool sample to find evidence of colon cancer. It was approved by the FDA in 2014, and its marketing on TV and in print media has been pretty aggressive. (Of course, that’s normal for new drugs and devices.)
I’m sure the makers of Cologuard, Exact Sciences, will use Colorectal Cancer Awareness Month to push consumers to “ask your doctor” about the “easy” and “non-invasive” screening test that doesn’t require any prep, anesthesia, or days off work.
All that sounds great, but is Cologuard really an effective alternative to the gold standard, a colonoscopy?
The short answer is no.
The pros and cons of Cologuard
Cologuard is labeled as a stool DNA test. Our intestines are lined with billions of cells that are constantly being sluffed off and pooped out. Cancers shed cells, too. Cologuard looks for DNA evidence of these cancer cells, as well as small amounts of blood.
Fecal occult blood tests also look for blood cells because cancers tend to bleed easily. FITs are more sensitive because they look for human blood; standard FOBTs pick up any blood, which is why you’re instructed not to eat red meat before taking the test.
A colonoscopy, on the other hand, actually gives the doctor “eyes on” the interior of your colon. If he or she sees a polyp, which can be precancerous, it can be removed and biopsied right away.
If any of the three fecal occult blood tests is positive, including Cologuard, a colonoscopy will have to be done anyway.
What are the pros of Cologuard?
- It’s easy.
- It’s easy.
- It’s easy.
- There is no bowel prep and it’s non-invasive.
- It’s sent to your home, and you mail it back to the laboratory and wait for the results.
- The $700 cost is covered by Medicare and some insurance companies (not all).
- It’s pretty effective at picking up cancers. Studies report Cologuard detects 92% of colon cancers. That sounds good, but…
What are the cons of Cologuard?
- It does a poor job (42%) of detecting precancerous polyps. That means a negative result can give a false sense of security because many cancers start as polyps.
- It has a high false positive rate (13%). A false positive means a colonoscopy has to be done even though there is nothing wrong. And because it’s now a “diagnostic” rather than a “screening” colonoscopy, insurance won’t cover it as a preventive test. False positives cause a lot of emotional distress, too.
- It’s unknown what the best screening interval is. Colonoscopy is every 10 years; FOBT and FIT are every year. The makers of Cologuard recommend every 3 years, but it’s a new product so there is no evidence to support that interval.
- It’s not recommended for anyone with a history of colon cancer or polyps, or IBS or other inflammatory bowel disease.
The bottom line (haha, yes I wrote that)
In January, the United States Preventive Services Task Force (USPSTF) updated its recommendations for colon cancer screening.
Overall, it gives colon cancer screening an “A” grade, meaning the benefits outweigh the risks.
It also provides a table listing the pros and cons of the various screening methods. Of Cologuard (listed as FIT-DNA), it says:
Specificity is lower than for FIT, resulting in more false-positive results, more diagnostic colonoscopies, and more associated adverse events per screening test.
There is insufficient evidence about appropriate longitudinal follow-up of abnormal findings after a negative diagnostic colonoscopy; may potentially lead to overly intensive surveillance due to provider and patient concerns over the genetic component of the test.
If you’re between the ages of 50 and 75, talk to your doctor about which colon cancer screening tool is best for you.
If you don’t have insurance and can’t afford a $3,000+ colonoscopy, or there is some other impediment, one of the stool tests may be appropriate.
For me, if I wanted a simple, inexpensive, non-invasive screening test, I would choose the FOBT or FIT. They may not be quite as sensitive as Cologuard, but the false positive rate is lower, and they are much, much cheaper than Cologuard. Under $50 versus $700.
Otherwise, a colonoscopy every 10 years, especially when the cost is covered by insurance, isn’t that big a deal.