Metformin does not affect cancer risk: a cohort study in the U.K. Clinical Practice Research Datalink analyzed like an intention-to-treat trial

Tsilidis KK, Capothanassi D, Allen NE, et al. Metformin does not affect cancer risk: a cohort study in the U.K. Clinical Practice Research Datalink analyzed like an intention-to-treat trial. Diabetes Care. 2014;37(9):2522-2532.

This study investigated cancer risk among metformin users vs users of sulfonylureas or other first-line oral antihyperglycemic therapies. This was a retrospective cohort study within UK Clinical Practice Research Datalink database; data were analyzed as “intention-to-treat” to emulate a clinical trial.

  • N=95,820 subjects
  • Newly diagnosed type 2 diabetes
  • Aged 35 to 90 years
  • Prescribed ≥1 antihyperglycemic agent during study index period
  • No cancer history

The main analysis compared initiators of metformin (biguanide) vs sulfonylureas. These medications were most commonly prescribed and had similar clinical indications. The study’s outcome assessment was first incident cancer cases.

Click on slide thumbnail to view larger. Slide available for download in the slide library.
Cancer Risk With Metformin Vs Sulfonylureas: Design   
Cancer Risk With Metformin Vs Sulfonylureas: Design 


Cancer incidence
There were 51,484 metformin users and 18,264 sulfonylurea users. Median follow-up: 5.1 years; maximum follow-up: 24 years.

3,805 first incident cancers identified:

  • 599 colorectal (353 metformin, 246 sulfonylurea)
  • 580 prostate (339 metformin, 241 sulfonylurea)
  • 468 lung (249 metformin, 219 sulfonylurea)
  • 460 post-menopausal breast (307 metformin, 153 sulfonylurea)

A similar incidence of the listed cancers and any other cancer types was seen with metformin and sulfonylureas over a maximum of 24 years of follow-up. (HR [95% CI] shown below.)

  • Total cancer*: 0.96 (0.89-1.04)
  • Colorectal cancer: 0.92 (0.76-1.13)
  • Prostate cancer: 1.02 (0.83-1.25)
  • Lung cancer: 0.85 (0.68-1.07)
  • Postmenopausal breast cancers: 1.03 (0.82-1.31)

There was no difference in cancer risk with metformin vs any other oral antihyperglycemic therapy, or when metformin or any other oral antihyperglycemic agents were added to monotherapy. All sensitivity analyses led to nearly identical results for total cancer or by cancer site.

Click on slide thumbnails to view larger. Slides available for download in the slide library.
Cancer Risk With Metformin Vs Sulfonylureas: Cancer Incidence   
Cancer Risk With Metformin Vs Sulfonylureas: Cancer Incidence 


Similar Cancer Risk With Metformin and Sulfonylureas Over Maximum 24 Year Follow-Up   
Similar Cancer Risk With Metformin and Sulfonylureas Over Maximum 24 Year Follow-Up  


*After adjustment for smoking status, body mass index (BMI), alcohol intake, aspirin or NSAID use, statins, diabetes duration, and year of first antihyperglycemic prescription.
Sulfonylurea users were the reference group

  

Any pharmacologic agents discussed are approved for use in the United States by the U.S. Food and Drug Administration (FDA) unless otherwise noted. Consult individual prescribing information for approved uses outside of the United States. 

September 2014 

This overview was created by KnowledgePoint360 Group, LLC, and was not associated with funding via an educational grant or a promotional/commercial interest.  

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Last Modified: 9/19/2014