For some people, one colonoscopy at age 50 may be enough for their whole lives, a new study suggests.
In the study, patients that 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.
The alternative methods, which include yearly stool tests, or imaging the colon with a CT scan every five years, cost less and produced fewer complications than did colonoscopies.
The findings suggest that, for people who received a negative result on their first colonoscopy, it is reasonable to switch to other, less invasive methods for subsequent screenings, the researchers said.
However, the findings were based on a computer model, which made certain assumptions that may not always hold true in the real world.
Overall, people who received any type of colon cancer screening had a lower risk of colon cancer compared with those who were not screened. "Which test you choose is less important" than the screening itself, said study researcher Amy Knudsen, of Massachusetts General Hospital.
The results are published today (Nov. 5) in the journal Annals of Internal Medicine.
Colon cancer screening
Current guidelines for colon cancer screening recommend several ways people can be screened starting at age 50. These guidelines assume that people will use one screening method their entire lives — for example, if you get a colonoscopy, you'll be told to come back for another in 10 years.
But people with a normal result on their first colonoscopy have a lower risk of developing colon cancer than people who have never been screened, and some have questioned whether additional colonoscopies are always needed.
In the new study, Knudsen and colleagues 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 studyunderwent 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 people over their lifetimes, and 2.5 to 3.5 deaths per 1,000 people, depending on the method used. In contrast, there were 31.3 cases per 1,000 people, and 12 deaths among those who received no further screening.
The rate of complications, such as bleeding, for colonoscopies was 21 complications per 1,000 people, but 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.
Although the screening methods tested in the study seemed equal in their abilities to reduce deaths from colon cancer, colonoscopies may be better at detecting precancer, and therefore, eliminating cancer before it starts, Dr. David Weinberg, of the Fox Chase Cancer Center and Dr. Robert Schoen, of the University of Pittsburgh Medical Center, wrote in an editorial accompanying the study.
This means that, in terms of quality of life, colonoscopies may still be the better choice. "Most of us would be willing to pay more to never have [colorectal cancer], rather than to suffer with cancer but survive," Weinberg and Schoen said.
In the U.S., a variety of screening options are likely to remain available, the editorial says.
"Patients, providers, and policymakers need to consider which outcomes they value most and the costs required to accomplish them," Weinberg and Schoen said.
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