Nancy N. Baxter, MD, PhD; Meredith A. Goldwasser, ScD; Lawrence F. Paszat, MD, MS; Refik Saskin, MSc; David R. Urbach, MD, MSc; Linda Rabeneck, MD, MPH
Colonoscopy is advocated for screening and prevention of colorectal cancer (CRC), but randomized trials supporting the benefit of this practice are not available.
To evaluate the association between colonoscopy and CRC deaths.
Population-based, caseâ€“control study.
Persons age 52 to 90 years who received a CRC diagnosis from January 1996 to December 2001 and died of CRC by December 2003. Five controls matched by age, sex, geographic location, and socioeconomic status were randomly selected for each case patient.
Administrative claims data were used to detect exposure to any colonoscopy and complete colonoscopy (to the cecum) from January 1992 to an index date 6 months before diagnosis in each case patient and the same assigned date in matched controls. Exposures in case patients and controls were compared by using conditional logistic regression to control for comorbid conditions. Secondary analyses were done to see whether associations differed by site of primary CRC, age, or sex.
10Â 292 case patients and 51Â 460 controls were identified; 719 case patients (7.0%) and 5031 controls (9.8%) had undergone colonoscopy. Compared with controls, case patients were less likely to have undergone any attempted colonoscopy (adjusted conditional odds ratio [OR], 0.69 [95% CI, 0.63 to 0.74; P < 0.001]) or complete colonoscopy (adjusted conditional OR, 0.63 [CI, 0.57 to 0.69; P < 0.001]). Complete colonoscopy was strongly associated with fewer deaths from left-sided CRC (adjusted conditional OR, 0.33 [CI, 0.28 to 0.39]) but not from right-sided CRC (adjusted conditional OR, 0.99 [CI, 0.86 to 1.14]).
Screening could not be differentiated from diagnostic procedures.
In usual practice, colonoscopy is associated with fewer deaths from CRC. This association is primarily limited to deaths from cancer developing in the left side of the colon.
Canadian Institutes of Health Research and American Society of Clinical Oncology.
The effect of colonoscopy on colorectal cancer (CRC) mortality is unknown.
By using a Canadian province-wide data set, the authors identified 10 292 case patients who died of CRC and, for each case patient, 5 matched controls who did not. A total of 7.0% of the case patients and 9.8% of the controls had colonoscopy. Colonoscopy was associated with fewer CRC deaths (odds ratio, 0.69 [95% CI, 0.63 to 0.74]). The odds ratios for death from CRC that developed in the left and right colon were 0.33 (CI, 0.28 to 0.39) and 0.99 (CI, 0.86 to 1.14), respectively.
This was an observational case–control study. The data set did not identify a reason for colonoscopy.
Colonoscopy may be much less effective in preventing death from CRC of the right colon compared with the left colon.
Values >0 indicate an increased risk with colonoscopy, and values <0 indicate a decreased risk (see Methods section).
Colonoscopy significantly reduces death from left-sided cancers, but is not effective at preventing death from right-sided cancers.
New York Medical College
February 17, 2017
We read with great interest the article by Baxter et al (1) regarding the association between colonoscopy and death from colorectal cancer. The results of this study are likely to have a far-reaching impact on the day-to-day practice of colonoscopy. Expertise of the colonoscopist in conjunction with the difficulties encountered in getting to the right side of colon are the factors likely to be responsible for the observed discrepancy between the left and right colon cancer related mortality. One thing strikes our minds while going through the article. In this high quality study, although cases were matched to controls for factors like sex, socioeconomic status, age and even geographical location; race and ethnicity as an important matching variable was missing in the data (2). In our view this is an important factor in the pathogenesis, progression and survival in colorectal carcinoma as has been shown in various previous studies (3-5).Rajeev Sharma, MDNew York Medical College (Metropolitan Hospital Program)New York-10029Pallawi Torka, MBBSAll India Institute of Medical SciencesNew Delhi, India-110029Potential Financial Conflict of Interests: NoneReferences1) Baxter NN, Goldwasser MA, Paszat LF, Saskin R, Urbach DR, Rabeneck L. Association of colonoscopy and death from colorectal cancer. Ann Intern Med. 2009; 150(1):1-8. [PMID: 19075198]2) Comparing colorectal cancer by race and ethnicity. Available at http://www.cdc.gov/cancer/Colorectal/statistics/race.htm. Accessed January 2009.3) Koo JH, Kin S, Wong C, Jalaludin B, Kneebone A, Connor SJ, et al. Clinical and pathologic outcomes of colorectal cancer in a multi-ethnic population. Clin Gastroenterol Hepatol. 2008 (9):1016-21.[PMID: 18558515]4) Chien C, Morimoto LM, Tom J, Li CI. Differences in colorectal carcinoma stage and survival by race and ethnicity. Cancer. 2005; 104(3):629-39. [PMID: 15983985]5) Brim H, Mokarram P, Naghibalhossaini F, Saberi-Firoozi M, Al-Mandhari M, Al-Mawaly K, et al. Impact of BRAF, MLH1 on the incidence of microsatellite instability high colorectal cancer in populations based study. Mol Cancer. 2008; 7:68. [PMID: 18718023]
Baxter NN, Goldwasser MA, Paszat LF, et al. Association of Colonoscopy and Death From Colorectal Cancer. Ann Intern Med. 2009;150:1–8. doi: https://doi.org/10.7326/0003-4819-150-1-200901060-00306
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Published: Ann Intern Med. 2009;150(1):1-8.
Colonoscopy/Sigmoidoscopy, Colorectal Cancer, Gastroenterology/Hepatology, Gastrointestinal Cancer, Hematology/Oncology.
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