Any type of colon cancer screening might work for people with a clear colonoscopy result initially, a model suggests.

Colonoscopy is the recommended screening method for colorectal cancer. Stool blood tests and surveillance of those with a family or personal history of colorectal cancer are also used in screening.


It is reasonable to use other methods to rescreen persons with negative colonoscopy results, a new modelling study concludes. (Jean-Paul Pelissier/Reuters)

For people aged 50 and older whose first colonoscopy is normal, researchers in the U.S. designed a model to compare alternative, less expensive strategies than repeating the colonoscopy after 10 years as current guidelines suggest.

"Compared with the currently recommended strategy of continuing colonoscopy every 10 years after an initial negative result, all other rescreening options we examined provide approximately the same benefit in life-years with fewer complications and at a lower cost," study author Amy Knudsen of Massachusetts General Hospital and her co-authors concluded in Tuesday's issue of the Annals of Internal Medicine.

"Therefore, it is reasonable to use other methods to rescreen persons with negative colonoscopy results."

The model considered both perfect and imperfect adherence to screening using:

  • Colonoscopy.
  • Fecal occult blood testing.
  • Fecal immunochemical testing.
  • Computed tomographic colongraphy (CTC).

The radiation risks of CTC were not factored into the analysis.

Any screening better than none

According to the model, with no screening beyond the initial colonoscopy, the lifetime incidence of colorectal cancer would be about 31 cases per 1,000 and the mortality about 12 deaths per 1,000.

Perfect adherence to colonoscopy every 10 years reduced the incidence to eight cases and 2.4 deaths per 1,000 persons — a 75 per cent to 80 per cent reduction, Dr. David Weinberg of Fox Chase Cancer Center in Philadelphia said in a journal editorial. 

Rescreening with other methods offered about the same mortality benefit with fewer complications than colonoscopy, the researchers concluded.

Colorectal screening is thought to reduce mortality by detecting earlier-stage cancer and removing polyps, precancerous lesions.

"Despite the difficulties in endorsing one test over another, this study emphasizes an important lesson: Any effective screening test is better than no test," Weinberg wrote.

"All forms of high-quality, consistent, serial screening seem effective."

Like all models, the one in the study is imprecise and makes assumptions and approximations, the editorial noted. The tool may not apply for those of other ages and genetic risk factors.

If the study's authors had measured differences in quality of life, they might have reached a different conclusion, "because most of us would be willing to pay more to never have colorectal cancer rather to suffer with cancer but survive," the editorial said.

Last week, an editorial in the New England Journal of Medicine estimated the relative risk reduction of 33 per cent with annual fecal occult-blood testing and 67 per cent for colonscopy.

Knudsen's research was funded by the U.S. National Cancer Institute and the U.S. National Institutes of Health.