Screening colonoscopy not helpful after age 70

The use of colonoscopy to screen for colorectal cancer may cause net harm if continued beyond age 70, according to a clinical- and cost-effective study. Fecal occult blood testing, on the other hand, remained both effective and cost-effective up until age 80 years.

Many guidelines recommend routine colorectal cancer screening for adults ages 50-75 years and individualized decisions in the elderly, including a 2008 recommendation statement from the US Preventive Services Task Force. But the effectiveness and incremental costs of continuing to routinely screen older people have not been well quantified in the literature, said at the annual meeting of the Society for General Internal Medicine.

Colorectal cancer and polyps are clearly more common in the elderly. “However, potential benefits of screening are limited. If it takes a long time for a polyp to become cancer, you need a relatively long life expectancy to make polyp removal worthwhile.”

With that in mind, colleagues developed a Markov decision model to assess the effectiveness and incremental cost-effectiveness of screening patients with a colonoscopy once each decade after age 50 and with fecal occult blood testing (FOBT) annually.

“Assumed an adherence rate of 60%, which is the ballpark, but may be a little optimistic compared to general colonoscopy adherence,” said the internal medicine faculty at the University of Michigan, Ann Arbor. Also an investigator at the Ann Arbor Veterans Affairs Center for Clinical Management Research.

“From 66 years to 85-plus the bleeding and perforation risks double,” according to Medicare data. For example, risk of bleeding was 0.49% for the 66- to 69-year-old cohort and increased to 1.15% among those 85 and older.

Their model also incorporated polyp prevalence data from autopsy and screening colonoscopy studies as well as rates of colorectal cancer from the surveillance Epidemiology, and End Results (SEER) database.

If colonoscopy is stopped at age 60 years, life expectancy beyond age 50 is 17.1651 years and screening costs $1,554 in 2006 dollars. (All life expectancies are discounted from a value of about 27 years, based on economic present-value analysis.) If colonoscopy stops at age 70, life expectancy increases very slightly to 17.1670 years beyond age 50 — “essentially a day” — and costs $1,623. But an additional colonoscopy at age 80 “actually causes harm.” The additional colonoscopy was associated with a decrease in life expectancy beyond age 50 to 17.1668 years and a cost of $1,648.

Also, “if a patient has actually had a colonoscopy at ages 50 and 60, then even a third one at age 70 ends up being harmful.”

“This fits with the recent US Preventive Services Task Force report to stop [screening] at age 75.” “From a population perspective, stopping colonoscopy after age 70 seems appropriate. But this does not apply equally to fecal occult blood testing.”

The study findings suggest that FOTB is effective and cost-effective for screening up to about age 80. For example, at age 76, FOBT is associated with a life expectancy of 17.1485 years beyond age 50 and costs $1,336. Continuing annually to age 80 is associated with an added life expectancy of 17.1489 years and a cost of $1,355.

Although the researchers found that FOBT screening does not cause harm. It costs more than $100,000 per life-year to continue screening beyond age 80.

The findings do not apply to people with no prior screening, “so if someone is 80 and has never been screened, it might be effective.” Also, the study did not address screening of high-risk patients and did not assess complex strategies such as two colonoscopies followed by subsequent FOBT that alternative strategies, such as mixed testing approaches, should be evaluated in future research.