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New study reports once in a lifetime colonoscopy may be enough

Robin Wulffson MD's picture
colonoscopy, colon cancer, screening, CT scan, occult blood test

Colonoscopy can diagnose colon cancer or pre-cancerous lesions at an early stage when a complete cure is possible; however, when many individuals balk at having an instrument inserted into a very private region of their anatomy. For those balkers, a new study may assuage their objections. Researchers affiliated with Massachusetts General Hospital suggested that for some people, one colonoscopy at age 50 may be enough for their whole lives. The findings were published on November 5 in the journal Annals of Internal medicine.

Current guidelines for colon cancer screening recommend several methods of cancer screening. For a colonoscopy, the guidelines recommend an initial screening at age 50 with a repeat procedure every 10 years. However, individuals with a normal result on their first colonoscopy have a lower risk of developing colon cancer than people who have never been screened; thus some question whether additional colonoscopies are always necessary. The alternative methods, which include annual stool tests, or imaging the colon with a CT scan every five years, are less expensive and have a lower complication rate than colonoscopies.

For the study, the researchers used a computer model to evaluate screening scenarios for people who had a negative result on a colonoscopy at age 50. The “virtual patients” in the study underwent either no additional screening, or received one of four possible screening methods from age 60 to 75: a colonoscopy every 10 years, a CT scan of the colon every five years, a yearly stool test called a fecal occult blood test or a yearly stool test called fecal immunochemical testing. The model took into account many factors, including how frequently colon cancers appear at each age, how fast they grow, and how effective various screening methods are in detecting them.

Among those who received some type of rescreening method, there were 7.7 to 12.6 cases of colon cancer per 1,000 individuals over their lifetimes, and 2.5 to 3.5 deaths per 1,000 individuals, depending on the method used. In contrast, there were 31.3 cases per 1,000 individuals, and 12 deaths among those who received no further screening.

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The rate of complications, such as bleeding, for colonoscopies was 21 complications per 1,000 people; however, there were about half that many complications for yearly stool testing and CT imaging. In addition, the cost of rescreening with colonoscopy was $3,840 per person over a lifetime, while the cost was $166 per person for CT scans, and about $780 per person for the stool tests.

The “virtual patients” who had no signs of cancer on their first colonoscopy lived just as long regardless of whether they received follow-up screening with a colonoscopy every 10 years, as is recommended, or were screened with alternative screening methods. Overall, people who received any type of colon cancer screening had a lower risk of colon cancer compared with those who were not screened. The researchers noted that, for individuals who received a negative result on their first colonoscopy, it is reasonable to switch to other, less invasive methods for subsequent screenings.

Take home message:
This study suggests that a single colonoscopy at age 50 followed by less invasive procedures in the future if the test is negative might be an adequate course of action. However, it must be noted that the results were derived from a computer model rather than real people.

Reference: Annals of Internal Medicine

See also: Colonoscopy screening has reduced incidence of colorectal cancer