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Individuals with diabetes who undergo colorectal cancer (CRC) screening, specifically colonoscopy, may be able to mitigate the risk for CRC.

T2D affects more than 10% of adults aged 65 and older, with non-Hispanic Black individuals and those of low socioeconomic status disproportionately affected by this condition, according to Shaneda Warren Andersen, MS, PhD. “This is also a population at higher risk for both T2D and colorectal cancer (CRC). Therefore, we were interested in studying the association between T2D and CRC,” she says.

Dr. Warren Andersen and Thomas Lawler, PhD, lead author of a study that appeared in JAMA Network Open, and colleagues used data from the Southern Community Cohort Study (SCCS), a large-scale prospective cohort of adults from the southeastern United States. SCCS participants completed detailed questionnaires centered on medical history, including a physician’s diagnosis of diabetes. “We identified participants who developed incident CRC after SCCS enrollment by linking to state cancer registries and the National Death Index,” Dr. Lawler notes. “We then conducted statistical analyses to determine that individuals living with T2D were more likely to develop CRC.”

Association May Be Interrupted by Colonoscopy Screening for CRC

Of 54,597 cohort participants, the median age at enrollment was 51; 64% were women, 66% were Black, and 53% had an annual income of less than $15.000. Of the 28,605 individuals without diabetes, 197 developed CRC, while 289 of 25,992 patients with diabetes developed CRC.

Receiving a diabetes diagnosis was correlated with a 47% increased risk for developing CRC when compared with individuals without a diabetes diagnosis, according to the study team. Furthermore, this association was more significant for participants without recent colonoscopy screenings (HR, 2.07; 95% CI, 1.16-3.67), those diagnosed with diabetes less than five years prior to completing the SCCS questionnaire (HR, 2.55; 95% CI, 1.77-3.67), and patients with a history of smoking (HR, 1.62; 95% CI, 1.14-2.31), the authors note.

Beyond traditional comorbidities associated with diabetes, T2D may also be a risk factor for CRC, the study authors point out. Their findings suggest that the association between diabetes and CRC may be disrupted by colonoscopy screening (Figure). “We observed that the link between T2D and CRC was attenuated among individuals who completed colonoscopies,” Dr. Warren Andersen says.

Dr. Lawler suggests that clinicians should educate patients about risk factors for CRC, including T2D and metabolic dysregulation, and highlight the importance of obtaining regular CRC screening for individuals who meet screening guidelines (ie, those aged 45 and older).

Lifestyle Intervention Helps Modify the Risk for CRC

“Using medications to control hyperglycemia in T2D may modify risk for CRC, including in underserved populations,” Dr. Warren Andersen says. Among the drugs that help manage diabetes, those in the GLP-receptor agonist class may have diverse effects on the risk for CRC by influencing serum insulin and insulin sensitivity as well as fasting and postprandial blood glucose. “There is also a significant need to determine how lifestyle interventions, including exercise and healthful diets, can modify CRC risk for individuals with diabetes.

The study authors hope these findings will help address racial and socioeconomic disparities in CRC. “Our results provide an important public health message that individuals with diabetes who undergo CRC screening, specifically colonoscopy, may be able to mitigate the risk for CRC,” Drs. Warren Andersen and Lawler conclude.