Patients with type 2 diabetes mellitus may be at increased colorectal cancer risk.
However, existing data are inconsistent.
Dr Paul Limburg and colleagues from Minnesota investigated colorectal cancer risks,overall, and by anatomic subsite.
The research team conducted a population-based inception cohort of clinically confirmed type 2 diabetes mellitus subjects.
The team identified 997 men and 978 women who first met standardized criteria for type 2 diabetes mellitus from 1970 to 1994.
The researchers followed the subjects forward in time until emigration, death, or until 1999.
Incident colorectal cancer cases were identified by review of inpatient and outpatient medical records.
The researchers estimated standardized incidence ratios and 95% confidence intervals.
The team then compared colorectal cancer incidence within the type 2 diabetes mellitus inception cohort with previously published rates for the Rochester general population.
|The interaction between type 2 diabetes mellitus and cigarette smoking was significant|
|American Journal of Gastroenterology|
The researchers identified over 19,158 person-years of follow-up, 51 incident colorectal cancer cases within the type 2 diabetes mellitus cohort.
However, the team expected only 37 cases.
Among men, type 2 diabetes mellitus was associated with increased overall, and proximal colorectal cancer risks.
The team noted that distal colorectal cancer risk was also increased, but the point estimate was not statistically significant.
Among women, the researchers found that type 2 diabetes mellitus was not a risk factor for overall, proximal, or distal colorectal cancer.
Within the type 2 diabetes mellitus cohort, current and former cigarette smokers were at higher colorectal cancer risk than never smokers.
The team observed that the interaction between type 2diabetes mellitus, and cigarette smoking status was statistically significant.
Dr Limburg's team commented, “In this population-based, retrospective cohort study, clinically confirmed type 2 diabetes mellitus was associated with increased colorectal cancer risk, predominantly among men.”
“Cigarette smoking appeared to positively modify diabetes mellitus -associated colorectal cancer risk, which to our knowledge has not been previously reported.”
“These data suggest that further investigation of potential interactions between endogenous and exogenous factors involved in colorectal carcinogenesis may help to clarify the magnitude and extent of colorectal cancer risk experienced by persons with type 2 diabetes mellitus.”