Effectiveness of Screening Colonoscopy to Prevent Colorectal Cancer Among Medicare Beneficiaries Aged 70 to 79 Years: A Prospective Observational Study

Ann Intern Med. 2017 Jan 3;166(1):18-26. doi: 10.7326/M16-0758. Epub 2016 Sep 27.


Background: No randomized, controlled trials of screening colonoscopy have been completed, and ongoing trials exclude persons aged 75 years or older. The Medicare program, however, reimburses screening colonoscopy without an upper age limit.

Objective: To evaluate the effectiveness and safety of screening colonoscopy to prevent colorectal cancer (CRC) in persons aged 70 to 74 and those aged 75 to 79 years.

Design: Large-scale, population-based, prospective study. The observational data were used to emulate a target trial with 2 groups: colonoscopy screening and no screening.

Setting: United States.

Participants: 1 355 692 Medicare beneficiaries (2004 to 2012) aged 70 to 79 years at average risk for CRC who used Medicare preventive services and had no previous diagnostic or surveillance colonoscopies in the past 5 years.

Measurements: 8-year risk for CRC and 30-day risk for adverse events.

Results: In beneficiaries aged 70 to 74 years, the 8-year risk for CRC was 2.19% (95% CI, 2.00% to 2.37%) in the screening colonoscopy group and 2.62% (CI, 2.56% to 2.67%) in the no-screening group (absolute risk difference, -0.42% [CI, -0.24% to -0.63%]). Among those aged 75 to 79 years, the 8-year risk for CRC was 2.84% (CI, 2.54% to 3.13%) in the screening colonoscopy group and 2.97% (CI, 2.92% to 3.03%) in the no-screening group (risk difference, -0.14% [CI, -0.41 to 0.16]). The excess 30-day risk for any adverse event in the colonoscopy group was 5.6 events per 1000 individuals (CI, 4.4 to 6.8) in the 70- to 74-year age group and 10.3 per 1000 (CI, 8.6 to 11.1) in the 75- to 79-year age group.

Limitation: CRC-specific mortality was not available, but CRC incidence and stage were studied at diagnosis.

Conclusion: Screening colonoscopy may have had a modest benefit in preventing CRC in beneficiaries aged 70 to 74 years and a smaller benefit in older beneficiaries. The risk for adverse events was low but greater among older persons.

Primary funding source: National Institutes of Health.

Publication types

  • Observational Study

MeSH terms

  • Aged
  • Colonoscopy* / adverse effects
  • Colorectal Neoplasms / diagnosis*
  • Colorectal Neoplasms / epidemiology
  • Colorectal Neoplasms / prevention & control*
  • Early Detection of Cancer* / adverse effects
  • Female
  • Humans
  • Incidence
  • Male
  • Mass Screening* / adverse effects
  • Medicare
  • Prospective Studies
  • United States / epidemiology