How a Delay in Colonoscopy Screening May Affect Cancer Risk

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Current guidelines recommend a colonoscopy starting at age 45 to 50, and then one every 10 years afterward if the results are negative. Those guidelines should still be followed, though for people at low risk for colon cancer, delays in colonoscopy screening may not dramatically affect cancer risk, a new study suggests.

The analysis, in Annals of Internal Medicine, included 165,887 men and women aged 50 to 66 who had a single negative colonoscopy. At 17 years after the initial test, compared with the general population, the group had a 72 percent lower rate of colon cancer and an 81 percent lower rate of death — not significantly different from results at 10 years and earlier.

But the finding pertains only to people with no polyps or other lesions, benign or malignant, at the first colonoscopy, and who are at low risk for colon cancer. It does not apply to anyone with a family history of colorectal cancer, inflammatory bowel conditions, or any other factors that increase colon cancer risk.

Most important, the finding depends on high-quality colonoscopy performed by a skilled endoscopist on a patient with adequate bowel preparation.

“It’s impossible to achieve zero risk,” said the lead author, Dr. Nastazja Dagny Pilonis, a researcher at the National Research Institute of Oncology in Warsaw. “But if you have a negative colonoscopy, and your bowel was adequately prepared, and your endoscopist was skilled, then you are at very low risk of colon cancer for at least 17 years.”