Should I Choose Cologuard Over Colonoscopy?

Cologuard has become a popular colon cancer screening option. Indeed, it has many advantages over the traditional colonoscopy. Refer to the list below.

No prep!
No prep!
No time off of work.
No driver needed.
No procedural risk.
Done at home.
No driving or other restrictions afterwards.\
Much less expensive.
Did I mention there is no prep:?

Wow, Cologuard sounds like it will be hard to beat. Not so fast!

Cologuard is a sophisticated stool DNA test that detects altered DNA as well as microscopic blood in the stool. Studies have shown that it detects over 90% of colon cancers. Keep in mind that the overwhelming number of patients undergoing colonoscopy do not have cancer so that this statistic doesn’t apply to them. How does this stool DNA test perform with respect to colon polyps, which are the target lesions during colonoscopy? Cologuard detects only 42% of larger precancerous polyps which seems to me to be rather lackluster performance. Large colon polyps are at greater risk of transforming to cancer over time. If you had one of them, would you opt for a screening test like Cologuard that had a 58% chance missing it? I doubt it. "Hey mom, great news! I got 42% on the math test!"

While a 13% false positive rate for Cologuard has been published, based on my own experience and that of my colleagues, I believe this is an underestimate.

Old Faithful Geyser in Yellowstone National Park

After Drinking a Colonoscopy Prep.

Colonoscopy is far superior in terms of detecting polyps and has the singular advantage of being able to remove them during the procedure. I am aware, of course, of the drawbacks of the colonoscopy experience, which are well known to readers of this blog. But it is clearly the best available option to reduce colon cancer risk. Ask your own doctor what screening test he or she has opted for, and I suspect most of them chose colonoscopy.

Is there a role for Cologuard? Definitely. While inferior to colonoscopy, it still offers a measure of protection. To compensate for its lower effectiveness, the test is advised at 3 year intervals, much more often than screening colonoscopies are. Also, I expect that ongoing research on stool DNA testing will yield much more effective products. So stay tuned.

So patients, do you prefer difficult, inconvenient but very effective or easy and much less accurate?

Editor’s Note: For 16 years, I've published weekly essays here on Blogspot, which will continue. I’ve now begun publishing my work on a new blogging platform, Substack, and I hope you’ll join me there. Please enter your email address at this link to receive my posts directly to your inbox.

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