11/10/2012 10:11 am ET

Colonoscopy: Only One Of These Tests May Be Necessary In A Lifetime, New Study Finds

A colonoscopy -- that dreaded test most post 50s are all too well familiar with -- may be the best way to screen for colon cancer, but that doesn't make the process any less cringe-inducing.

Most guidelines recommend that people screen once ever 10 years for colorectal cancer starting at age 50 and up until they turn 70. But researchers have recently determined that some people only need to undergo one colonoscopy in their lifetime, though some in the medical community warn against taking this new finding any further than speculation.

In a study published in the Annals of Internal Medicine, researchers found that those who tested negative for colon cancer in their first colonoscopy lived just as long as those who received the recommend follow-up colonoscopy every 10 years or sought alternative screening.

The findings were based on a computer model, whose "patients" either received no additional screening or underwent one of four follow-up screening tests from 60-75: the regular colonoscopy every decade; a CT scan of the colon every five years; or two types of annual stool tests, fecal immunochemical testing or fecal occult blood testing, according to the study. If the hypothetical patients followed all rescreening procedures to a T, Knudsen said:

"...the model predicted 7.7 to 12.6 cases of colorectal cancer per 1,000 people over their lifetimes, and 2.4 to 3.5 deaths from colorectal cancer per 1,000 people, depending on the rescreening method used. In contrast, the model predicted 31.3 cases per 1,000 people, and 11.9 deaths among those who received no further screening."

"Right now there is no colorectal cancer screening test that will reduce your risk of colorectal cancer to 0. Our study found that rescreening with any method after a negative colonoscopy substantially reduces colorectal cancer risk compared with no further screening," lead study researcher Amy Knudsen of Massachusetts General Hospital told Huff/Post50. "That you get screened again appears to be more important than which rescreening approach you opt for."

The computer-based nature of the findings is what has some in the medical field weary. "The single most limiting factor of such simulation models is the power and accuracy of the assumptions," Alan G. Thorson, president of the American Society of Colon and Rectal Surgeons, told Huff/Post50. "Regardless of the strengths or weaknesses of the assumptions used in this study, it is still a single study. Screening guidelines are established based on a review of all available pertinent literature, never on a single study. While this study may play an important role in the screening guidelines development process it should not be used, and patients should not be encouraged to use it, in making personal screening decisions. Suggesting such represents an irresponsible use of the medical literature."

Knudsen said she hoped the study "will provide more information to patients and their doctors about the options available for rescreening after a negative colonoscopy.

"Rescreening with colonoscopy or CT imaging of the colon prevents more cases of colorectal cancer than rescreening with fecal occult blood tests. Colonoscopy is invasive, while CTC and the fecal occult blood tests are not. The risks of complications are higher with colonoscopy, you may need to take a day off from work to have it done, and you need someone to drive you to and from the procedure.

"However, colonoscopy is screening and treatment at once, since detected adenomas can be removed right then and there," she continued. "With all of the other tests, if you have a positive test result you have to have a colonoscopy in order to realize any benefit. And finally, fecal occult blood tests have to be performed regularly in order for them to be as effective as other options. In light of these differences, it’s clear that no one test will be right for everyone. You should talk with your doctor to decide which approach is best for you given your risk and your preferences. No test is effective unless it is done, so opting for an approach that you’re willing to comply with is key."

It seems like modern medicine is trying to find a way to make the business around colonoscopies as relatively painless as possible. A Mayo Clinic in Phoenix recently required patients to take four pills instead of two or more liters of laxatives to prep for a virtual colonoscopy. More than 1,000 readers rejoiced at the news, with one saying, "unconsciousness was a blessing" compared to the "seven pints of the foul brew" one typically has to throw back in preparation for the test.



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