A study, reported in Gastroenterology (October 2004), indicated that individuals with type 2 diabetes who need long-term insulin therapy may be more susceptible to colorectal cancer. The study involved 24,918 patients with type 2 diabetes from a United Kingdom database. The analysis included individuals with at least 3 years of follow-up data after their initial diagnosis. The participants who were diagnosed with colorectal cancer within the first year of insulin therapy were excluded.
The research showed that the longer patients received insulin the higher the risk of colorectal cancer. Individuals who received at least 3 years of insulin therapy had 3 times the risk of developing that cancer, compared with patients who received no insulin. The risk of individuals on >5 years of insulin therapy was 4 times higher, compared with the noninsulin group.
Gene Barrett, MD, professor of medicine at the University of Virginia, said that the study offered no conclusive evidence of an association between insulin dependence and colorectal cancer.