This systematic review looked at observational studies of a link between treatment with insulin, whether type 1 or type 2 diabetes, and the incidence of cancer of any type.
In people with diabetes, is treatment with insulin, as compared to other treatment, associated with an increased risk of cancer?
The reviewers found 15 studies with 562,045 participants. They pooled the data from these studies and found that cancer was more common in people who were using insulin. The relative risk was 1.39 (95% confidence interval 1.14 to 1.70).
Subgroup analysis by cancer type showed a stronger association with pancreatic cancer than with colorectal cancer, and no association with other types of cancer.
Users of this research should consider:
- Of course, insulin treatment is associated with more serious cases of diabetes. It may be this, rather than insulin, that is at the root of the association with cancer. The fact that the strongest association was found with pancreatic cancer might suggest that this is the case.
- Indeed, it is likely that there are other confounding factors at play, including ones we don’t know about.
- There is insufficient information available open access to evaluate the reliability of this research.
- Did the reviewers do enough to find all of the relevant research?
- Was there blind, independent study selection, evaluation and data extraction?
- Were the studies good quality? Were they prospective studies that looked at new cases of cancer over a period of time, or were they retrospective?
- Was there appropriate adjustment for other risk factors?
- Were the subgroup analyses planned in advance?
Janghorbani M, Dehghani M, Salehi-Marzijarani M. Systematic Review and Meta-analysis of Insulin Therapy and Risk of Cancer. Horm Cancer. 2012 Apr 24. [Epub ahead of print]