Protection from colorectal cancer after colonoscopy: a population-based, case-control study

Ann Intern Med. 2011 Jan 4;154(1):22-30. doi: 10.7326/0003-4819-154-1-201101040-00004.


Background: Colonoscopy with detection and removal of adenomas is considered a powerful tool to reduce colorectal cancer (CRC) incidence. However, the degree of protection achievable in a population setting with high-quality colonoscopy resources remains to be quantified.

Objective: To assess the association between previous colonoscopy and risk for CRC.

Design: Population-based case-control study.

Setting: Rhine-Neckar region of Germany.

Patients: A total of 1688 case patients with colorectal cancer and 1932 control participants aged 50 years or older.

Measurements: A detailed lifetime history of CRC risk factors and preventive factors, including history and results of previous colonoscopies, and of medical data obtained by self-reports and medical records. Odds ratios of CRC associated with colonoscopy in the preceding 10 years were estimated, after adjustment for sex, age, education level, participation in a general health screening examination, family history of CRC, smoking status, body mass index, and use of nonsteroidal anti-inflammatory drugs or hormone replacement therapy.

Results: Overall, colonoscopy in the preceding 10 years was associated with 77% lower risk for CRC. Adjusted odds ratios for any CRC, right-sided CRC, and left-sided CRC were 0.23 (95% CI, 0.19 to 0.27), 0.44 (CI, 0.35 to 0.55), and 0.16 (CI, 0.12 to 0.20), respectively. Strong risk reduction was observed for all cancer stages and all ages, except for right-sided cancer in persons aged 50 to 59 years. Risk reduction increased over the years in both the right and the left colon.

Limitation: The study was observational, with potential for residual confounding and selection bias.

Conclusion: Colonoscopy with polypectomy can be associated with strongly reduced risk for CRC in the population setting. Aside from strong risk reduction with respect to left-sided CRC, risk reduction of more than 50% was also seen for right-sided colon cancer.

Primary funding source: German Research Council and German Federal Ministry of Education and Research.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenomatous Polyps / diagnosis*
  • Adenomatous Polyps / surgery*
  • Aged
  • Aged, 80 and over
  • Case-Control Studies
  • Colonic Polyps / diagnosis*
  • Colonic Polyps / surgery*
  • Colonoscopy*
  • Colorectal Neoplasms / diagnosis
  • Colorectal Neoplasms / epidemiology
  • Colorectal Neoplasms / prevention & control*
  • Colorectal Neoplasms / surgery
  • Digestive System Surgical Procedures
  • Female
  • Germany / epidemiology
  • Humans
  • Incidence
  • Male
  • Middle Aged
  • Odds Ratio
  • Risk Factors