Adapting capsule endoscopy for colorectal cancer screening
(17 October 2009: VIDYYA MEDICAL NEWS SERVICE) -- The Agency for Healthcare Research and Quality recommends colorectal cancer screening for average-risk adults between the ages of 50 and 75 with one of the following methods: annual fecal occult blood testing, sigmoidoscopy every 5 years, or colonoscopy every 10 years. However, as of 2005, only 59 percent of people aged 50 or older had been screened according to these recommendations, and only 50 percent had had a colorectal endoscopy procedure (either sigmoidoscopy or colonoscopy, screening techniques that can both visualize cancer in the colon and rectum and remove precancerous polyps) within the past 10 years.
Many factors contribute to this low rate of screening endoscopy, including a shortage of medical professionals trained to perform the techniques, disparities in access, and people’s reluctance to undergo an invasive screening procedure.
“Having a tube placed for a colonoscopy is something that’s uncomfortable for a lot of people to think about,” said Dr. Stephen Taplin, senior scientist in NCI’s Division of Cancer Control and Population Sciences’ Applied Research Program (ARP).
One way to boost colorectal cancer screening rates may be to develop new screening technologies that are simpler, more accessible, and more acceptable to participants. A tiny, futuristic device smaller than the tip of one’s finger called the capsule endoscope is currently being tested and improved for what its developers hope will be a place in the cancer screening armamentarium.
Visualizing the “Black Box” of the Body
Originally developed to explore the small intestines, the small-bowel capsule endoscope (CE) is a tiny device about the size of a large vitamin pill, containing a light, a miniature camera, and a transmitter that sends images to a recording device worn by the patient during the procedure. A patient swallows the CE just like a pill, and the capsule is propelled through the digestive system by the normal movement of the intestines, transmitting pictures of the intestinal walls throughout its passage.
Approved by the FDA for the diagnosis of small bowel diseases in 2001, CE revolutionized small bowel medicine by allowing noninvasive imaging of part of the body that had been previously inaccessible except through surgical exploration.
One of the three companies that manufacture small-bowel CEs has now developed a version for the colon, in the hope of producing a less invasive alternative to traditional endoscopy for colorectal cancer screening. The colon CE has not been approved by the FDA for use in the United States, but it is being tested in clinical trials and explored by researchers interested in its potential applications.
Unmet Hopes in First Large Trial
The new colon CE—which contains two video imagers, one at each end of the capsule, and captures pictures at a rate of four frames per second—was recently tested in an international clinical trial led by researchers from the Université Libre de Bruxelles in Belgium and the manufacturer, Given Imaging, from Yoqneam, Israel. The researchers enrolled 332 patients with known or suspected colon disease into the trial. Each patient underwent both CE and standard colonoscopy on either the same or successive days.
Although the capsule was found to be safe, the preparation regimen that was required to cleanse the gut (including a clear liquid diet and laxatives) was more involved than the regimen for a standard colonoscopy, and the sensitivity of the capsule was not as high as colonoscopy (which is thought to have a maximum sensitivity of just over 90 percent). Advanced adenomas of any size were detected in 52 patients by colonoscopy, but in only 44 patients by CE. Nineteen cancers were detected by colonoscopy, but only 14 of those were visualized by the capsule.
“With the capsule’s relatively low sensitivity for the detection of colorectal lesions, [and] its requirement for more extensive bowel-cleansing regimens as compared with colonoscopy and CT colonography…colon capsule endoscopy cannot be recommended at this time,” concluded Dr. Michael Bretthauer of Oslo University Hospital Rikshospitalet in an editorial that accompanied the trial’s publication in the July 16 New England Journal of Medicine.
Challenges and Promises
A number of challenges lie in the way of colon CE being ready for the clinic, including improving sensitivity, which is related to the amount of data that can be captured by the imaging device, and the human error that can arise in analyzing large amounts of captured video. Reducing the cost per procedure will also be necessary.
Dr. Ram Sriram, a group leader with the National Institute of Standards and Technology Manufacturing Engineering Laboratory, and his colleagues in the Information Technology Laboratory, with input from the Asian Institute of Gastroenterology, are designing software to help automate image analysis for the small-bowel CE to speed analysis time (and thereby decrease cost) and reduce the likelihood of human error. Similar software could potentially help reduce the cost and increase the accuracy of colon CE, as well, but first the capsule must be able to capture enough data for the software engineers to analyze.
The colon is much wider than the small bowel, making it more challenging to develop a sufficiently sensitive colon CE. Even with a slightly larger size, “the capsule tends to move around a lot and doesn’t have a focus area, so you’re not getting all the pictures that you need,” explained Dr. Sriram. “Once they can take enough pictures, engineers can do image processing to make the technology more sensitive.”
The issue of simplifying the complicated bowel preparation currently required for colon CE is also “not trivial—it’s a huge issue, because the preparation is another aspect of colonoscopy that a lot of people don’t like,” said Dr. Taplin.
But the potential advantages of colon CE will likely keep researchers focused on improving the technology. For example, CE holds promise for telemedicine applications, explained Dr. Sriram, such as helping patients in remote areas who cannot travel to see a specialist for screening or diagnosis.
Also, if an improved, lower-cost colon CE could be administered by a primary care physician instead of a specialist, “that could remove the barrier of the scheduling process, and make it easier for patients to get access,” said Dr. Taplin. “Improving any kind of screening process is not just about improving the technology; it’s about streamlining the whole process to make it work.”
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