Racial disparities in colorectal cancer incidence by type 2 diabetes mellitus status.

Purpose: Type 2 diabetes mellitus (T2DM) prevalence has increased dramatically in the United States since the early 1970s. Though T2DM is known to be associated with colorectal cancer (CRC), information on racial differences in the relationship between T2DM and CRC is limited.

Methods: Using a retrospective cohort design, we compared the association between T2DM and CRC, including subsites of the colon, in African Americans (AAs) and European Americans (EAs) in South Carolina, a region with large racial disparities in rates of both diseases. A total of 91,836 individuals who were ≥30 years old on 1 January 1990 and had ≥12 months of South Carolina Medicaid eligibility between 1 January 1990 and 31 December 1995 were included in the analyses. Cancer data from 1996 to 2007 included information on anatomic subsite.

Results: Subjects who had T2DM (n = 6,006) were >50 % more likely to be diagnosed with colon cancer compared to those without T2DM (n = 85,681). The association between T2DM and colon cancer was higher in AAs [odds ratio (OR) = 1.72 (95 % confidence interval: 1.21, 2.46); n = 47,984] than among EAs (OR = 1.24; 0.73, 2.11; n = 43,703). Overall, individuals with T2DM were over twice as likely to be diagnosed with in situ or local colon cancer (OR = 2.12; 1.40, 3.22; n = 191) compared to those without T2DM, with a higher likelihood among AAs (OR = 2.49; 1.52, 4.09; n = 113).

Conclusions: Results from a Medicaid population in a high-risk region of the United States showed an increased likelihood of CRC with T2DM and suggest a racial disparity that disfavors AAs and provides further impetus for efforts aimed at diabetes prevention in this group.