Insulin therapy and colorectal cancer risk among type 2 diabetes mellitus patients

Glucose-lowering agents and cancer mortality rates in type 2 diabetes: assessing effects of time-varying exposure

“…Our findings are in line with those of several other epidemiological studies [28][29][30][31][32]. An earlier case-control study by Evans et al found that metformin was associated with a statistically significant 23% reduction in the risk of cancer compared with sulfonylurea therapy among patients with type 2 diabetes, after adjusting for various clinical factors [28].…”

“…The age-and sex-adjusted hazard ratio for colorectal cancer was 2.1 for ≥1 year of insulin use. Moreover, the authors observed an adjusted odds ratio of 1.2 for colorectal cancer for each incremental year of insulin therapy [31]. More recently, Chung et al confirmed these findings that chronic insulin therapy was associated with an increased risk of colorectal adenoma in people with type 2 diabetes [32].…”

Does diabetes therapy influence the risk of cancer?

“…More specifically, there is concern that high insulin levels and associated changes in the IGF-1 axis may accelerate the progression of existing cancer foci. Insulin treatment of type 2 diabetes was, for example, associated with a twofold increase in the risk of colorectal cancer, compared with other therapies, in an analysis that adjusted for prior use of metformin or sulfonylureas [15]. The same analysis reported that cancer risk increased by an estimated 20% for each year of insulin therapy.…”

Insulin, glucose and the increased risk of cancer in patients with type 2 diabetes

“…Recent observational studies have linked increasing insulin exposure with an increased risk of cancer incidence or increased cancer mortality rates [2,4,6,7]. As observational studies, they have a number of limitations and by themselves do not allow inference of causation.…”

“…This has been highlighted by observational studies suggesting a protective effect on cancer outcomes for metformin [1][2][3][4] and glitazones [5], but on the other hand a potential increased cancer risk associated with exogenous insulin [2,4,6,7], insulin analogues [8,9] and sulfonylurea therapies [2,4,7].…”