Diabetes drug offers no benefit to non-diabetic patients
CHICAGO – Metformin, when added to docetaxel, has no impact on outcomes among patients with metastatic castration-resistant prostate cancer, researchers reported here at the 55th annual meeting of the American Society of Clinical Oncology.
In the first clinical trial to test the question of whether metformin can make a difference in outcome, researchers said that addition of the drug fails to reduce prostate-specific antigen (PSA) levels any better than docetaxel alone, said Marc Pujalte Martin, MD, of Centre Antoine Lacassagne, Universite Cote d’Azur, Nice, France, reporting the TAXOMET trial results.
Pujalte Martin said 66% of 50 patients treated with metformin achieved the primary endpoint of a 50% or greater response in PSA levels compared to 63% of 49 patients treated with docetaxel alone (P=0.94), a non-significant finding.
Progression free survival with metformin was a median of 7.4 months; with placebo, it was 5.6 months. Overall survival was a median of 24.6 months if the patients were on metformin and a median of 19.6 months if the patients were on placebo. Neither secondary outcome result was statistically significant, he said.
“We found that addition of metformin to docetaxel did not seem to have a meaningful clinical benefit in this setting,” Pujalte Martin said in his oral presentation.
He noted that the treatment with metformin did not result in any cases of hypoglycemia or in the development of unexpected adverse events.
The main adverse effect of metformin is an increase in diarrhea, which was reflected in the trial. About 70% of the patients on metformin plus docetaxel reported any grade diarrhea compared with 50% of the docetaxel plus placebo patients.
The invited discussant, Mary-Ellen Taplin, MD, director of clinical research at the Lank Center for Genitourinary Oncology at Dana-Farber Cancer Institute/Brigham & Women’s Hospital, Boston, said, “I want to congratulate Dr. Martin and his team of investigators for completing a prospective, randomized, placebo-controlled trial that will impact clinical care, as these data should reduce off-label use of metformin. Given the high rate of Grade 1 and Grade 2 toxicities with metformin which approached 70% in the context of chemotherapy, this type of treatment is not innocuous.”
Martin disclosed no relevant relationships with industry.
Taplin disclosed relevant relationships with Amgen, Astellas Pharma, AstraZeneca, Bayer, Clovis Oncology, Guidepoint Global, Incyte, Janssen-Ortho, Medivation, Myovant Sciences, Pfizer, Research to Practice, Tokai Pharmaceutical, and UpToDate.
Pujalte Martin M, et al “TAXOMET: A French prospective multicenter randomized controlled phase II study comparing docetaxel plus metformin versus docetaxel plus placebo in mCRPC” ASCO 2019; Abstract 5004.
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