Colorectal cancer screening may be cost-effective beyond age 75 in previously unscreened patients, modeling study suggests

Colorectal cancer screening (colonoscopy, sigmoidoscopy, or fecal immunohistochemical testing) may be cost-effective for patients older than 75 who have never been previously screened, according to a new study.

The U.S. Preventive Services Task Force recommends against routine colorectal cancer screening in patients older than 75 who have previously been screened but does not address older patients who have never been screened. Researchers performed a microsimulation modeling study to examine when colorectal cancer screening should be considered in unscreened elderly patients, as well as which screening test might be indicated at each age.

Data from observational and experimental studies were used, and the target population was unscreened patients between 76 to 90 years of age who had no, moderate, and severe comorbid conditions. The interventions examined were one-time colonoscopy, sigmoidoscopy, or fecal immunochemical testing (FIT). Outcome measures were quality-adjusted life-years (QALYs) gained, costs, and costs per QALY gained. The study was published in the June 3 Annals of Internal Medicine.

In the base-case analysis, colorectal cancer screening was cost-effective in unscreened elderly patients with no comorbid conditions until age 86. Colonoscopy was indicated until age 83, sigmoidoscopy was indicated at age 84, and FIT was indicated at ages 85 and 86. When unscreened patients with moderate comorbid conditions were considered, screening was cost-effective until age 83, with colonoscopy indicated until age 80, sigmoidoscopy indicated until age 81, and FIT indicated at ages 82 and 83.

The cost-effective upper age limit for screening in unscreened patients with severe comorbid conditions was 80 years, with colonoscopy indicated up to age 77, sigmoidoscopy indicated up to age 78, and FIT indicated at ages 79 and 80. All of these calculations assumed a willingness-to-pay threshold of $100,000 per QALY gained. Reducing the threshold to $50,000 per QALY gained decreased the upper ages at which screening was cost-effective to 84, 80, and 77 years in patients with no, moderate, and severe comorbid conditions, respectively.

The authors noted that their model considered only patients at average risk for colorectal cancer and that they did not analyze patients by sex and race. However, they concluded that based on their study, colorectal cancer screening should be considered “well beyond age 75 years” in elderly U.S. patients who had not previously been screened.

Future research, the authors said, should attempt to determine the optimal number of FIT screenings in relatively young elderly patients who do not want to have screening colonoscopy or sigmoidoscopy. In addition, they said, more studies are necessary on the effect of the benefits, burdens, and harms of screening on patients' decision making and on the appropriate age to stop screening in adequately screened patients based on comorbid conditions.