Pill Camera Not as Good as Colonoscopy for Detecting GI Lesions

Nick Mulcahy

September 18, 2010

July 15, 2009 — It's swallowable, allows for visualization of the colon's mucosa, and, in the opinion of one expert, has a likely role in the future of colorectal cancer screening.

However, as currently designed and employed, an endoscope in a capsule (PillCam SB, Given Imaging) has a low sensitivity for detecting colonic polyps and cancers, compared with colonoscopy, according to a study published July 16 in the New England Journal of Medicine.

Many patients are reluctant to undergo colonoscopy because of its "perceived inconvenience, discomfort, or embarrassment," write the study authors, led by Andre Van Gossum, MD, of the Erasme University Hospital in Brussels, Belgium. Hence the appeal of this portable minimally invasive technology, they suggest.

However, in a multicenter study of 320 patients with known or suspected colonic disease, the sensitivity and specificity of capsule endoscopy for detecting polyps that were 6 mm or larger were 64% and 84%, respectively, write Dr. Van Gossum and his European colleagues.

In the study, all capsule endoscopies were followed by colonoscopy within a day's time; the results of the colonoscopy were used to comparatively determine the capsule technology's sensitivity and specificity.

The capsule endoscope is not approved for use in the colon by the US Food and Drug Administration, said Virender Sharma, MD, from the Mayo Clinic in Scottsdale, Arizona. However, the device is approved for use in the small intestine, he told Medscape Oncology.

Capsule endoscope will not replace colonoscopy anytime soon and will have very selective use.

If and when it is approved for use in the colon, the device's "best use will be in patients who do not want to have a colonoscopy, those at high risk for colonoscopy complications, and those in which the endoscopist was not able to complete the procedure," Dr. Sharma added. He also emphasized that an approved "capsule endoscope will not replace colonoscopy anytime soon and will have very selective use."

Colonoscopy is the best test for detecting colon polyps.

Although acknowledging that colonoscopy is an invasive procedure that requires sedation, time off work, and transportation assistance for the patient, Dr. Sharma stressed its virtues. "Colonoscopy is the best test for detecting colon polyps and the only test that has the ability to remove colon polyps and prevent progression to colon cancer," he said.

Nevertheless, Dr. Sharma, who uses the capsule at the Mayo Clinic, believes the technology has a future in colon cancer screening "once the test is optimized and accuracy is comparable to colonoscopy."

Cleanliness Counts

Of the 320 patients, 221 (69.1%) excreted the capsule within 6 hours of ingestion and 297 (92.8%) excreted it within 10 hours. All of the patients excreted the capsule naturally, although in 1 patient (0.3%), it was not until 4 weeks later, write the authors.

Lead author Dr. Van Gossum told Medscape Oncology that after the pill is excreted and the video is downloaded, a review of a single patient takes about 20 to 30 minutes. The device acquires images at a rate of 4 frames per second.

In addition to evaluating the capsule's performance in detecting lesions 6 mm or larger, the investigators reviewed detection of lesions smaller than 6 mm.

The sensitivity and specificity of capsule endoscopy for detecting polyps that were less than 6 mm were 61% and 82%, respectively.

Of the 19 cancers detected by colonoscopy, 14 were detected by the capsule endoscopy (sensitivity, 74%).

Mild to moderate adverse events were reported in 26 patients (7.9%) and were mostly a result of the colon preparation, said the authors.

Colon cleanliness is an important dimension in how the capsule endoscope works, assert the authors. "The sensitivity was significantly higher in patients with good to excellent cleanliness as compared with the patients with poor or fair cleanliness," they write. Still, Dr. Van Gossum said that the majority (>70%) of the patients had good to excellent cleanliness.

Nonetheless, the authors believe that the technology can be improved along these lines. "Efforts should be made to improve the colon-preparation regimen for capsule endoscopy," they write.

The study authors report a variety of conflicts of interest, including 2 authors who have received either consulting or lecture fees from Given Imaging, the maker of the Pill Cam SB.

New Engl J Med. 2009;361:264-270.

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