Cologuard is a sophisticated stool test that checks for microscopic blood and altered DNA which can signal the presence of colon cancer or precancerous polyps. Some patients are attracted to this non-invasive option rather than to traditional colonoscopy experience which includes the ever popular cathartic cocktail.
This test was approved by the Food and Drug Administration
(FDA) in 2014. The test was initially
quite popular as patients and physicians were enthusiastic about this new colon
cancer screening option. Often in medicine,
what’s new becomes popular but initial enthusiasm tends to ebb over time. (With time, the initial safety and efficacy
reports for medicines and diagnostic tests may not be sustained. This is why post-marketing surveillance after
initial approval is so critical.) Patients were advised early on, as they are
now, that a positive Cologuard test meant that a follow up colonoscopy was
mandatory. Certainly, when I order this test for a
patient who is aiming to avoid a colonoscopy, I secure their agreement to a
subsequent colon exam if the stool test result is positive.
Gastroenterologists and physicians in those early years
after FDA approval regarded positive Cologuard results very seriously. This was not yesterday’s stool smear for
microscopic blood. Cologuard detected
actual DNA fragments that could be derived from actual cancer or significant
colon polyps.
In those early years, when I was evaluating positive
Cologuard patients, I was concerned that these colons had a high probability
of harboring significant lesions. When I
was doing colonoscopies on such patients and discovered no abnormalities, I
would prolong the exam to re-examine various regions of the colon concerned
that I had overlooked the important finding that caused the positive
Cologuard. I often had lingering
worry afterwards that I had missed a significant finding.
As the years went by, and the medical profession accumulated
more experience, we learned that false positive Cologuard tests were common. Now, when these colon exams are normal, I
recognize that this is a fortunate and common outcome.
Many positive Cologuard patients are often positive that
they have cancer. The vast majority of
them will have either a normal colonoscopy or benign polyps. So, while I still recommend that every individual
with a positive Cologuard result pursue the joy of colonoscopy, the probability
that they have an actual cancer is quite low.
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