Can metformin extend survival of prostate cancer patients with (or without) diabetes?

A retrospective analysis of data from  > 3,800 Canadian men has suggested that diabetic men who also had prostate cancer and were being treated with a commonly used, generic drug called metformin have a reduced risk for death from prostate cancer.

This new paper by Margel et al., just published on line in the Journal of Clinical Oncology, appears to supplement other, earlier evidence that metformin may have anti-cancer properties — not just in the management of prostate cancer but possible across a spectrum of tumor types.

Margel and his colleagues wanted to work out whether — among men who had diabetes — there was any association between time on treatment with metformin after an initial diagnosis with prostate cancer and all-cause and prostate cancer-specific mortality. To do this, they used data from administrative (as opposed to clinical) databases in the province of Ontario. They then analyzed these data for information about patients > 66 years of age with incident diabetes who went on to be diagnosed with prostate cancer.

Here is what they found:

  • The databases included 3,837 patients who met the eligibility criteria.
  • The average (median) age of the patients at diagnosis with prostate cancer was 75 years.
  • Patients received treatment with metformin for a median time of
    • 19 months before their diagnosis with prostate cancer
    • Nearly 9 months after their diagnosis with prostate cancer.
  • Median follow-up was 4.64 years.
  • During the follow-up period
    • 1,343/3,837 patients (35 percent) died of all causes.
    • 291/3,837 patients (7.6 percent) died of prostate cancer.
  • The cumulative duration of metformin treatment after diagnosis with prostate cancer was associated with a significant decrease in risk for both prostate cancer-specific and all-cause mortality in a dose-dependent fashion.
    • The adjusted hazard ratio (aHR) for prostate cancer-specific mortality was 0.76 for each additional 6 months of metformin use.
    • The aHR for all-cause mortality declined over time from 0.76 in the first 6 months of follow-up to 0.93 between 24 and 30 months.
  • There was no apparent relationship between cumulative use of other antidiabetic drugs and either all-cause or prostate cancer-specific mortality.
  • No direct cause-and-effect relationship between metformin use and survival could be established.

There has been a lot of earlier work that was designed to discover whether metformin was able reduce the risk of getting prostate cancer in the first place, but most of the data from these studies were negative. By comparison, the current study certainly suggests that metformin may improve survival in diabetics who are subsequently diagnosed with prostate cancer … but we really need a randomized clinical trial to be able to prove this.

Additional information about this study and related expert opinion can be found in other commentaries on the HealthDay and the MedPage Today web sites.

On the HealthDay web site, there is a statement that the research team is planning to test metformin in patients with prostate cancerwho do  not have diabetes. According to Dr. Margel,  “Metformin is very safe to use among nondiabetic patients.” Common side effects of metformin treatment include mild diarrhea and stomach problems that commonly die down after a couple of weeks on treatment.)

One Response

  1. Hope so…

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