Insulin treatment may be associated with an increased risk of cancer

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.

Clinical question:

In people with diabetes, is treatment with insulin, as compared to other treatment, associated with an increased risk of cancer?

The evidence

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.

Appraisal hints:

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?

Reference

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]

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Badenoch

Badenoch
I am an information scientist with an interest in making knowledge from systematic research more accessible to people who need it. This means you. I've been attempting this in the area of Evidence-Based Health Care since 1995. So far the results have been mixed. For some reason we expected busy clinicians to search databases and appraise papers instead of seeing patients. We also expected publishers to make the research freely available to the people who paid for it.. Ha! Hence The National Elf service.

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