Monday, October 21, 2013

FIT colorectal screening: is annual testing necessary?

- Jennifer Middleton, MD, MPH

One of the POEMs in last week's American Family Physician discussed a recent study from the Netherlands regarding fecal immunochemical testing (FIT) for colorectal cancer screening; the researchers studied the prevalence of screening, rate of positive screening results, and rate of identified colorectal neoplasia.  They found that screening annually did not increase the yield of new colorectal cancer cases compared with screening every 2 to 3 years.

Having a viable alternative to colonoscopy is vitally important to ensuring that our patients get colorectal cancer screening.  Colorectal cancer is the fourth most common form of cancer in the U.S., but at least 1/3 of U.S. adults aged 50-75 are not getting adequate screening.  A survey by the Colon Cancer Alliance found that fear of the bowel prep and procedure keeps many adults from getting a screening colonoscopy.  I have several patients who appreciate having the option of a less invasive screening tool.

At first, our only alternative to offer was the fecal occult blood test (FOBT), but then FIT came onto the scene with several advantages. Certain fruits and vegetables, along with red meat, can cause false positives with FOBT, and vitamin C supplementation can cause false negatives.  FIT, by looking at globin instead of heme, eliminates the effect from these heme-based test confounders.

I still remember convincing our practice to switch from FOBT to FIT after learning these points.  But we experienced an unexpected result - fewer of our patients were returning the FIT than the FOBT.  It turned out that the FIT kit instructions were difficult for many of our patients to follow. Take a look and compare for yourselves:


With FOBT, patients just have to smear some stool onto a card.  But, with FIT, patients have to use a paintbrush over the surface of the stool, transferring this water instead of stool to the card, all the while making sure that no toilet paper gets into the toilet bowl.  So, which is worse: dietary restrictions with FOBT, or more complicated instructions with FIT? Perhaps the answer for your patients is different than it was for ours.

What I appreciated about the article featured in AFP, though, was the change in screening interval.  The researchers found that more patients participated in the biannual and triannual screening than they did if it was annual; screening less often resulted in more people getting screened.  If other researchers can validate this point on a larger scale, this expanded screening interval may tip the balance in favor of FIT once and for all. For now, the American College of Physicians, as reviewed in AFP last year, advises that physicians may offer average risk patients FIT, FOBT, flexible sigmoidoscopy, or colonoscopy.  This article, and several more, are available in the AFP By Topic for colorectal cancer.

So, how are you tackling colorectal cancer screening in your office?