Diabetes mellitus is an independent risk factor for colorectal cancer.
BACKGROUND
Epidemiological studies have suggested positive associations between diabetes and colorectal cancer. However, the findings were inconsistent, especially regarding specific sex or cancer subsite.


OBJECTIVE
To conduct a systematic review with meta-analysis to examine the association of diabetes mellitus with risk of colorectal cancer and to investigate whether the association is dependent on sex, cancer subsite, race/ethnicity, or duration of diabetes.


METHODS
Relevant studies were identified by searching Pubmed to May 12, 2011. The reference lists of identified articles were also reviewed. Two authors independently selected the studies and extracted relevant data. The study quality was assessed.


RESULTS
Thirty-nine studies (28 cohort studies and 11 case-control studies) were included in the final analysis. Compared with non-diabetic subjects, the pooled risk estimate of colorectal cancer for diabetic subjects was 1.29 (95% CI = 1.23-1.35). The subgroup analyses revealed that the risk was significantly increased for both genders, for every cancer subsite, and for both short duration and long duration of diabetes. Exposure to diabetes increased the risk of colorectal cancer for White and Asian, whereas there was no evidence of such an association either among Black or native Hawaiians.


CONCLUSIONS
Our results confirmed that subjects with diabetes are at modestly increased risk of developing colorectal cancer.
Cancer Center, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wu Han, China. leisun2011@hotmail.com
Lei
L
Sun
Shiying
S
Yu
D000328:Adult; D017677:Age Distribution; D000369:Aged, 80 and over; D016022:Case-Control Studies; D015331:Cohort Studies; D015179:Colorectal Neoplasms / Q000175:diagnosis* / Q000453:epidemiology*; D015897:Comorbidity; D003920:Diabetes Mellitus / Q000175:diagnosis* / Q000453:epidemiology*; D003922:Diabetes Mellitus, Type 1 / Q000175:diagnosis / Q000453:epidemiology; D003924:Diabetes Mellitus, Type 2 / Q000175:diagnosis / Q000453:epidemiology; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D018570:Risk Assessment; D017678:Sex Distribution; D016019:Survival Analysis