Meta-Analysis
Copyright ©The Author(s) 2015. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. May 21, 2015; 21(19): 6026-6031
Published online May 21, 2015. doi: 10.3748/wjg.v21.i19.6026
Association of type 2 diabetes mellitus and the risk of colorectal cancer: A meta-analysis and systematic review
Salman Yousuf Guraya
Salman Yousuf Guraya, College of Medicine, Taibah University, Almadinah Almunawwarah 41477, Saudi Arabia
Author contributions: Guraya SY contributed to the data collection, data analysis, manuscript writing, and revisions of the article.
Conflict-of-interest: No conflict of interest declared.
Data sharing: Technical appendix and output files of the statistical analysis are available from the corresponding author at salmanguraya@gmail.com; Informed consent for data sharing was not obtained from the participants as the presented data are anonymized and the risk of identification is very low.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Correspondence to: Salman Yousuf Guraya, Professor, Consultant Colorectal Surgeon, College of Medicine, Taibah University, PO Box 30054, Almadinah Almunawwarah 41477, Saudi Arabia. salmanguraya@gmail.com
Telephone: +966-553375969 Fax: +966-148-461407
Received: October 23, 2014
Peer-review started: October 26, 2014
First decision: November 14, 2014
Revised: November 26, 2014
Accepted: December 16, 2014
Article in press: December 16, 2014
Published online: May 21, 2015
Abstract

AIM: To provide a quantitative assessment of the association between type 2 diabetes mellitus (T2DM) and the risk of colorectal cancer (CRC).

METHODS: Systematic review was conducted thorough MEDLINE, EMBASE, Cochrane Library, and ISI Web of knowledge databases till 31st January 2014. This meta-analysis included the cohort studies that illustrated relative risk (RR) or odds ratio estimates with 95%CI for the predictive risk of CRC by T2DM. Summary relative risks with 95%CI were analyzed by using an effects summary ratio model. Heterogeneity among studies was assessed by the Cochran’s Q and I2 statistics.

RESULTS: The meta analysis of 8 finally selected studies showed a positive correlation of T2DM with the risk of CRC as depicted by effects summary RR of 1.21 (95%CI: 1.02-1.42). Diabetic women showed greater risk of developing CRC as their effect summary RR of 1.22 (95%CI: 1.01-49) with significant overall Z test at 5% level of significance was higher than the effect summary RR of 1.17 (95%CI: 1.00-1.37) of men showing insignificant Z test. The effect summary RR of 1.19 with 95%CI of 1.07-1.33 indicate a positive relationship between DM and increased risk of CRC with significant heterogeneity (I2 = 92% and P-value < 0.05).

CONCLUSION: Results from this systematic review and meta-analysis report that diabetic people have an increased risk of CRC as compared to non-diabetics.

Keywords: Colorectal cancer, Type 2 diabetes mellitus, Risk ratio, Gastrointestinal cancers, Cancer statistics

Core tip: The prevalence of diabetes for all age groups worldwide is estimated to be 2.8% in 2000 and 4.4% in 2030. Type 2 diabetes mellitus (T2DM) is associated with increased insulin resistance and insulin has been reported to exhibit procarcinogenic effects in a number of human systems including colon and rectum. This meta-analysis of 8 relevant cohort studies showed an increased risk for colorectal carcinoma by T2DM, and this association was more evident in diabetic women than men.