Wednesday, March 5, 2008

Colonoscopies Miss Colon Cancer

A report in the Journal of the American Medical Association found that flat colon polyps, which are harder to see than raised polyps, were ten times more likely to be cancer. Japanese gastroenterologists found these harder to detect flat polyps by using a dye during colonoscopy. The study also found that having a colonoscopy wasn't enough for adequate screening, but rather how much time and care the doctor took to examine the colon. From the report:

  • The growths tend to be smaller when they are cancerous — the size of a nickel instead of a quarter — and are level with the colon wall or depressed like a pothole. They blend in with the surrounding tissue and are difficult to spot.
  • While knobby polyps were found in four times as many participants, more than half the colon cancers found — 15 of 28 — were in flat and depressed growths. Thirteen were in polyps.
  • Undetected flat growths could explain some mysterious "interval cancers" that show up between screenings in people who have regular colonoscopies, experts said.
Currently the recommended guidelines for colon cancer screening include having a colonoscopy every 10 years starting at the age 50. Recently updated colon cancer screening guidelines from the American Cancer Society now include virtual colonoscopy as well as a stool DNA test. These two newer techniques join screening by using a flexible sigmoidoscopy every 5 years with or without annual stool testing for occult blood or screening via a barium enema. For individuals at average risk (i.e. no family history of colon cancer or no personal history of medical problems like ulcerative colitis that increases an individual's risk of colon cancer greatly), any one of these interventions should begin at age 50.

While I understand the addition of a virtual colonoscopy, which may be more acceptable for the public to accept rather than having a endoscope inserted into the colon for evaluation, I'm not so sure that the radiation exposure related to this screening test is justified. I suspect in the end it was added because:

  • The biggest issue is not which screening a patient should get, but that patients come in for screening. All colon cancer deaths can be averted through screening and early treatment, but only 30 percent of people recommended to get screenings actually do, according to the Cancer Society.
  • "The challenge we have is getting people to participate in screenings," said Jack Mandel, an Emory University epidemiologist who has studied colon cancer screening tests. "We can prevent these deaths."

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