Oh, Joy! The Prospect Of Laxative-Free Colonoscopies

Even now, weeks after my first colonoscopy, certain tastes and smells still trigger odd sensory flashbacks to the gallon of salty-swampy laxative liquid I had to glug to clean out my intestines before the procedure.

The taste didn't seem so bad at first. I scoffed at all the whiners who have made the nastiness of colonoscopy prep so legendary. But near the end of the gallon, I found myself gagging and forced to suck on lollipops to help the swallowing along. Not that I'd ever skip the test. Colon cancer is too common and deadly, killing 50,000 Americans a year, and the effectiveness data on colonoscopies look good. Still, I couldn't help wondering aloud: Does it really, truly have to be like this?

So even though the prospect of a laxative-free colonoscopy is years away, I can make no pretense of journalistic objectivity. I'm overjoyed to share this news: A new study out of Massachusetts General Hospital, following about 600 patients, suggests that a colonoscopy without the noxious preliminaries is feasible.

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The point isn’t just to make life easier for people getting colonoscopies. It’s to help persuade them to get the test in the first place.

[/module]I did my due diligence: I asked the study's leader, Dr. Michael Zalis, director of CT Colonography in the hospital's imaging department, whether any potential financial conflicts needed to be disclosed — a start-up to develop laxative-free colonoscopies, that kind of thing? But no, no such disclosures, he said. The study was funded by the American Cancer Society, General Electric and the National Institutes of Health. Good enough — please sign me up for ten years from now.

A bit of background: Medical innovators had already invented the "virtual colonoscopy," in which a patient's innards are inspected using an abdominal CT scan rather than by inserting a long fiber-optic tube with a camera and a light on the end. But the patient still has to go through the colon-cleansing prep. The new study, just out in the May 15 Annals of Internal Medicine, takes the "virtual" one step farther: it uses software and a special contrast agent to make the colon cleanse virtual as well.

The point isn't just to make life easier for people getting colonoscopies; It's to help persuade them to get the test in the first place. Only about half of adults follow the recommendations for getting tested — which include universal testing for people over 50 — and surveys find that the nastiness of the prep is part of the problem.

Let me cut to the chase: If all goes well, I asked Dr. Zalis, how soon might the virtual cleansing be available? Conservatively speaking, he said, at least one more study is needed to confirm his team's results, and that will probably take at least three years.

From the Mass. General press release:

"If these results hold up in larger trials, we would expect this procedure would first be offered to moderate-risk patients who are otherwise unable or unwilling to be screened," he adds.  "If we can validate that this form of CT colonography performs reasonably well for screening and is easier for patients, it could have a significant impact on reducing the incidence of colon cancer and related cancer deaths."

And the price? Currently, virtual colonoscopies cost about one-third as much as the standard optical colonoscopies, Dr. Zalis said, "and I would expect that this non-cathartic version, the laxative-free version, would cost the same" as a virtual colonoscopy. The contrast used is a minimal expense, he said, and patients only need to ingest a quantity the size of a ketchup packet with each meal for two days before the exam.

The risks? The paper found that the technique wasn't quite as good as traditional colonoscopies at detecting smaller polyps, but that it did detect the larger polyps that are most likely to develop into cancer.

"The bottom line," Dr. Zalis said, "is that people should participate in screening, and optical colonoscopy, which has been around for 30 years, is a very good test. The trouble is that not enough people are willing or able to undertake it. So it's clear we need other options.

"So if you’re talking about beginning patients who are otherwise not being screened, if you give them a new option which, even if it doesn’t perform quite as well, appears to perform very adequately for the most significant polyps, that's already an incremental benefit from where we are right now. And this laxative-free technique is probably going to evolve significantly. We're just getting started."

So how does it work? In my primitive fashion, I imagine the patient swallowing some blue dye, which turns all their food and former food blue, and then some handy-dandy scanning software subtracts anything blue and voila! The colon tissue!

No, not really, Dr. Zalis said. The contrast agent is clear; it can't be seen at all. But it does absorb X-ray. So it shows up on a CT scan.

"So what happens is: if you give small amounts of this, it mixes with the food and water a patient takes in, so all ingested material becomes distinct in appearance on a CT scan," he said. "But importantly, the contrast agent is not absorbed by the bowel wall or polyps, so in cross-section on a CT scan, the polyps and normal structures on the bowel wall are very distinct from ingested material. The software selectively removes the ingested material and laves untouches the polyps and bowel wall."

And by the way, the radiation for a "screening" CT likes this is one-fifth the usual level for a diagnostic CT, he said.

From the press release:

Preparation for the procedure tested in the current study involves two days of a low-fiber diet and oral ingestion of small doses of a contrast agent to label fecal material in the colon.  Software programs developed by the MGH team subtract labeled feces from the CT images and analyze the images for the presence of lesions – primarily adenomas, the type of polyps most likely to develop into cancer.  The investigators recruited patients scheduled for screening colonoscopy between June 2005 and October 2010 at the MGH, Brigham and Women's Hospital, North Shore Medical Center and the Veteran's Administration Medical Center at the University of California at San Francisco; and 604 patients completed the full protocol.

Study results showed the effectiveness of computer-assisted, laxative-free CT colonography to be comparable to that of optical colonoscopy for detecting adenomas 10 mm or larger.  While it did not do as well finding smaller polyps, those lesions are less likely to show cellular changes associated with higher risk for cancer development.  Among colonoscopy-confirmed lesions that showed such risk-associated changes, 85 percent were 10 mm or larger.  Three cases of colon cancer were diagnosed among the study group, and all of those lesions were 10 mm or larger and were detected by both screening methods.  Participants completing the survey indicated that laxative-free CT colonography is more comfortable and easier to prepare for, and it was the preferred screening method for 62 percent of respondents.