Neoadjuvant metformin in localized prostate cancer: not ready for prime time yet

A paper presented on Saturday at the annual meeting of the American Association for Cancer Research in Chicago has suggested the possibility of better outcomes after radical prostatectomy among men taking the diabetes drug metformin before their surgery … but the data are from a very small study.

According to the paper by Joshua et al., their study was a single-center, Phase II trial of neoadjuvant metformin (at a dose of 500 mg three times daily) in men with localized prostate cancer, all of whom were scheduled for radical prostatectomy. The rationale for this trial is that in the past couple of years there have been suggestions that metformin might have a variety of anti-cancerous effects in several different types of cancer.

Here are the key study findings:

  • The trial enrolled a total of 24 patients — of whom 22 were evaluable.
  • The average (median) age of the patients was 64 years (range, 45 to 70 years).
  • The patients’ average (median) PSA level at the start of the trial was 6 ng/ml (range, 3.22 to 36.11 ng/ml).
  • The average (median) duration of metformin treatment was 41 days (range 18 to 81 days).
  • There were no reports of grade 3 adverse events.
  • Significant pre- and post-surgical changes were noted in
    • Serum IGF1 levels (p = 0.02)
    • Fasting glucose levels (p = 0.03)
    • Body mass index or BMI (p < 0.01)
    • Waist/hip ratio (p<0.01).
  • There was a trend toward a PSA reduction (p = 0.08).

Joshua et al. conclude that neoadjuvant metformin “is well tolerated prior to radical prostatectomy” aznd appears to have some potentially promising effects on metabolic parameters that may be relevant to prostate cancer outomes.

While this paper is scientifically interesting, and metformin is a widely used and relatively safe drug, The “New” Prostate Cancer InfoLink does not think that this study would in any way justify the widespread use of neoadjuvant metformin among men with prostate cancer scheduled for radical surgery. We clearly need data from a larger, randomized, double-blind trial to justify such use of metformin in the management of localized prostate cancer.

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