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Capsule Endoscopy vs. Colonoscopy for Detecting Colonic Lesions

With colonoscopy as the standard of comparison, a new capsule endoscopy system adequately imaged the colon and rectum in 93% of patients.

Capsule endoscopy (CE) is a less invasive method of detecting colorectal cancer (CRC) than colonoscopy. Now, a CE system that incorporates a battery-conserving "sleep mode" has been developed specifically to visualize the colon. Using colonoscopy as the standard of comparison, researchers evaluated the PillCam COLON capsule's sensitivity and specificity for identifying polyps, advanced adenomas, and cancer.

The prospective, international, industry-sponsored study involved 328 patients (mean age, 59) with known or suspected colorectal neoplasia. Patients underwent extensive bowel preparation before ingestion of capsules. The capsule had cameras on both ends; each camera acquired images at two frames per second. Colonoscopy was performed after capsule excretion or 10 hours after ingestion, whichever came first. The capsule went into "sleep mode" 3 minutes after ingestion, for a duration of 1 hour and 45 minutes, during which the capsule normally transited most of the small bowel and arrived at the terminal ileum.

The average life of the capsule's battery after "wake-up" was 10 hours. The capsule was excreted before the end of the battery's lifetime and adequately imaged the colon and rectum in 93% of patients. CE's per-patient sensitivity and specificity for polyps 6 mm were 64% and 84%, respectively. (Sensitivity remained relatively flat with increasing polyp size: 60% for polyps 10 mm.) Sensitivity and specificity for advanced adenomas 6 mm were 73% and 79% and for cancer were 74% and 74%. For CE, bowel preparation was graded as good or excellent in 72% of patients; for colonoscopy, bowel preparation was good or excellent in 87% of patients (P<0.001). In patients with good or excellent bowel preparation, the sensitivity and specificity for polyps 6 mm were 75% and 84%; these percentages were 42% and 84% in patients with poor or fair preparation.

Comment: Could CE have a role in CRC screening? In this regard, CE is more analogous to computed tomography colonography (CTC) than it is to conventional colonoscopy. Both are diagnosis-only tests, and neither has proven to be as effective as colonoscopy for detecting colorectal neoplasia. However, a more important question might be whether CE would improve CRC screening adherence rates in patients who are unwilling to undergo colonoscopy. This question is currently difficult to answer, as it is for CTC — hundreds of CTC studies have been reported, but in only one study did researchers evaluate its effect on CRC screening adherence rates (JW Gastroenterol Mar 7 2008). We hope that we will learn something about CE's effect on adherence much sooner than we have about CTC. If people who refuse to undergo colonoscopy would accept screening with CE, we would likely accept some lower degree of polyp and cancer detection in exchange.

Two major challenges must be overcome before CE performance will improve. One is camera frame speed, which currently is too slow for adequate imaging when the capsule is moving quickly through the colon. (However, this problem should be correctable technically.) The other challenge is achieving good-quality bowel preparation. Despite the fact that patients who are preparing for CE are advised to ingest greater amounts of laxatives than patients preparing for colonoscopy, the quality of preparation for CE is typically worse. Perhaps we should redefine "poor preparation" for CE because the problem is not retained fecal debris but, rather, mucus particles that are suspended in the colonic fluid through which the capsule passes. During colonoscopy, this fluid would be removed by suction, but, in CE, the fluid obstructs the view. The solution to this problem might be prescribing a mucolytic or mucus suppressant, rather than more laxatives.

The messages to CE developers seem clear: Increase the frame speed, demonstrate early on that CE affects adherence, and find a way to get rid of the mucus.

— Douglas K. Rex, MD

Dr. Rex receives research support and is a consultant to Given Imaging, which manufactures the PillCam COLON capsule.

Published in Journal Watch Gastroenterology July 17, 2009

Citation(s):

Van Gossum A et al. Capsule endoscopy versus colonoscopy for the detection of polyps and cancer. N Engl J Med 2009 Jul 16; 361:264.

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