Effect of colonoscopy on colorectal cancer incidence and mortality: an instrumental variable analysis

• Published in: Gastrointestinal endoscopy Vol. 76; no. 2; pp. 355 - 364.e1
• Main Authors: Jacob, Binu J., MSc, Moineddin, Rahim, PhD, Sutradhar, Rinku, PhD, Baxter, Nancy N., MD, PhD, Urbach, David R., MD, MSc
• Format: Journal Article
• Language: English
• Published: Maryland heights, MO Mosby, Inc 01.08.2012; Elsevier
• Subjects: Aged; Biological and medical sciences; Cohort Studies; Colonoscopy - utilization; Colorectal Neoplasms - diagnosis; Colorectal Neoplasms - epidemiology; Colorectal Neoplasms - mortality; Colorectal Neoplasms - prevention & control; Digestive system. Abdomen; Early Detection of Cancer - methods; Early Detection of Cancer - utilization; Endoscopy; Female; Gastroenterology and Hepatology; Gastroenterology. Liver. Pancreas. Abdomen; Humans; Incidence; Investigative techniques, diagnostic techniques (general aspects); Male; Medical sciences; Middle Aged; Ontario - epidemiology; Outcome Assessment (Health Care); Practice Patterns, Physicians' - statistics & numerical data; Registries; Retrospective Studies; Stomach. Duodenum. Small intestine. Colon. Rectum. Anus; Survival Analysis; Tumors; Ontario; colorectal cancer; PCP; primary care physician; CRC; Rectal disease; Prognosis; Mortality; Colorectal cancer; Malignant tumor; Epidemiology; Incidence; Colonic disease; Colonoscopy; Gastroenterology; Digestive diseases; Intestinal disease; Endoscopy; Cancer
• ISSN: 0016-5107; 1097-6779
• DOI: 10.1016/j.gie.2012.03.247

Background Using population-based health services information to estimate the effectiveness of colonoscopy on colorectal cancer (CRC) outcomes is prone to selection bias. Objective To determine the effect of colonoscopy on CRC incidence and mortality. Design Population-based retrospective cohort study. Setting Ontario provincial health data information. Patients This study involved average-risk persons aged 50 to 74 years from 1996 to 2000 who were alive and free of CRC on January 1, 2001. Intervention Colonoscopy between 1996 and 2000. Main Outcome Measurements CRC incidence and mortality from 2001 to 2007. Results The study cohort contained 1,089,998 persons, 7.9% of whom had undergone a colonoscopy between 1996 and 2000. Using primary care physician rate of discretionary colonoscopy as an instrumental variable, the receipt of colonoscopy was associated with a 0.60% (95% confidence interval [CI], 0.31%-0.78%) absolute reduction in the 7-year colorectal cancer incidence and a 0.17% (95% CI, 0.14%-0.21%) absolute reduction in the 5-year risk of death caused by CRC. This corresponds to a 48% relative decrease in CRC incidence (risk ratio [RR] 0.52; 95% CI, 0.34-0.76) and 81% decrease in mortality caused by CRC (RR 0.19, 95% CI, 0.07-0.47). In subgroup analyses, the reduction in the risk of death due to CRC was larger in women than men. The reduction in CRC incidence was larger for complete colonoscopies and for left-sided cancers. Limitations Instrumental variable methods estimate only the marginal effect on the population studied. Conclusion Increased use of colonoscopy procedures is associated with a reduction in the incidence and mortality of CRC in the population studied.