Journal Article

Diabetes Mellitus and Risk of Colorectal Cancer: A Meta-Analysis

Susanna C. Larsson, Nicola Orsini and Alicja Wolk

in JNCI: Journal of the National Cancer Institute

Volume 97, issue 22, pages 1679-1687
Published in print November 2005 | ISSN: 0027-8874
Published online November 2005 | e-ISSN: 1460-2105 | DOI: http://dx.doi.org/10.1093/jnci/dji375
Diabetes Mellitus and Risk of Colorectal Cancer: A Meta-Analysis

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Background: Diabetes has been associated with an increased risk of colorectal cancer in most, but not all, studies. Findings have also been inconclusive with regard to sex and subsite in the colorectum. To resolve these inconsistencies, we conducted a meta-analysis of published data on the association between diabetes and the incidence and mortality of colorectal cancer. Methods: We identified studies by a literature search of Medline from January 1, 1966, through July 31, 2005, and by searching the reference lists of pertinent articles. Summary relative risks (RRs) with 95% confidence intervals (CIs) were calculated with a random-effects model. All statistical tests were two-sided. Results: Analysis of 15 studies (six case–control and nine cohort studies), including 2 593 935 participants, found that diabetes was associated with an increased risk of colorectal cancer, compared with no diabetes (summary RR of colorectal cancer incidence = 1.30, 95% CI = 1.20 to 1.40), without heterogeneity between studies (Pheterogeneity = .21). These results were consistent between case–control and cohort studies and between studies conducted in the United States and in Europe. The association between diabetes and colorectal cancer incidence did not differ statistically significantly by sex (summary RR among women = 1.33, 95% CI = 1.23 to 1.44; summary RR among men = 1.29, 95% CI = 1.15 to 1.44; Pheterogeneity = .26) or by cancer subsite (summary RR for colon = 1.43, 95% CI = 1.28 to 1.60; summary RR for rectum = 1.33, 95% CI = 1.14 to 1.54; Pheterogeneity = .42). Diabetes was positively associated with colorectal cancer mortality (summary RR = 1.26, 95% CI = 1.05 to 1.50), but there was evidence for heterogeneity between studies (Pheterogeneity = .04). Conclusions: Our findings strongly support a relationship between diabetes and increased risk of colon and rectal cancer in both women and men.

Journal Article.  6193 words.  Illustrated.

Subjects: Medical Oncology

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