Evidence building that colonoscopy screening should start earlier

A US study provides “compelling” evidence that colonoscopy at age 45-49 decreases the risk of developing colorectal cancer.

The observational study, published in Gastroenterology, compared the association between colonoscopy and the subsequent risk of colorectal cancer in 45-49 year-olds and 50-54 year-olds from a Florida cohort.

It found CRC incidence in the younger age group was 20.8 per 100,000 person-years with exposure to colonoscopy and nearly 50% higher at 30.6 per 100,000 person-years without exposure to colonoscopy.

In the older age group CRC incidence was 19.0 per 100,000 person-years with exposure to colonoscopy, and more than double the rate at 51.9 per 100,000 person-years without exposure to colonoscopy.

Adjusted hazard rates for developing CRC in the groups with versus without colonoscopy were 0.49 (95% CI 0.43-0.56, p<0.0001) at ages 45-49 and 0.32 (95% CI 0.29-0.34, p<0.0001) at 50-54 years.

The hazard ratios were not affected by further adjustment for sex and race or ethnicity.

In both age groups, CRC rates were higher after colonoscopies performed for bleeding, anaemia or abnormal radiographic findings than for other symptoms.

The findings suggest a strong inverse association between exposure to colonoscopy at ages 45-49 years or 50-54 years and subsequent CRC incidence.

“These results address the pressing need for data on CRC outcomes after colonoscopy at ages 45-49 years in order to inform guidelines and clinical practice on the optimal age to begin CRC screening,” the study said.

The researchers calculated that earlier colonoscopy could reduce CRC incidence by approximately 43%.

To date the American Cancer Society guideline recommends people at average risk of colorectal cancer start regular screening at age 45.

However as previously reported in the limbic, draft guidelines from the USPSTF also recommend lowering the screening age to 45 years and are expected to be confirmed.

“It is questionable whether a randomised controlled trial of CRC screening at ages 45-49 years can be conducted, given the requirement for even larger sample sizes than any CRC screening trial to date due to the lower event rate in younger people,” the study said.

“We expect that data like ours will be supplemented by observational studies on lesion detection rates during screening at ages 45-49 years, followed by extrapolation to infer long-term outcomes.”

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