Follow-up colonoscopy could substantially cut cancer risk

CANCER DIGEST – April 29, 2017 – As much as you might hate it, undergoing that follow-up colonoscopy might cut your risk of colorectal cancer by half, a new analysis of colonoscopy data shows.

British researchers looked at data for more than 250,000 patients and identified approximately 12,000 people who were diagnosed with intermediate-risk adenomas across 17 UK hospitals. These patients were monitored over an eight year period, and the incidence of bowel cancer was compared in those who had a follow-up colonoscopy with those who had not.

They found that a subgroup of patients within the intermediate-risk group, who either had large adenomas (2 cm or larger), or advanced pathology (changed DNA that is not yet cancerous), or polyps in the upper half of the large bowel were at a higher risk of developing bowel cancer. These 'higher-risk' patients appeared to benefit substantially from at least one follow-up colonoscopy.

 After a median follow-up of 7 to 9 years, 210 colorectal cancers were diagnosed. Among the 12,000 people diagnosed with intermediate risk polyps, 5019 (42%) patients did not undergo colonoscopy and 6925 (58%) underwent one or more colonoscopies. Compared to those who had no exams, those with one colonoscopy had a 57 percent lower risk of colorectal cancer, and those who had a second colonoscopy had a further 31 percent to 84 percent lower risk of cancer compared to those with no colonoscopies.

Without colonoscopy, colorectal cancer occurred significantly more often in patients who had a suboptimal quality colonoscopy, or polyps in the proximal area of the intestines, or a high-grade, or large adenoma (benign tumor larger than 0.9 inches) at baseline compared to the general population.

By contrast, the intermediate-risk patients found to have none of these features, colorectal cancer occurred significantly less often than it occurs in the general population. For this group of patients, the researchers suggest that follow-up colonoscopies may not be warranted at all if the initial colonoscopy is of high quality.