Does Metformin have a role in metastatic breast cancer?
Studies indicate maybe yes and no.
Metformin and chemotherapy. (Please read my prior blogs on studies which DO show it helps). But in transparency, these studies did not show an effect.
- MYME phase II trial added metformin to first-line chemotherapy in nondiabetic patients with HER2-negative metastatic breast cancer.
- Randomized to chemo alone or metformin 1000mg 2x/day.
- No benefits were seen in progression free survival or overall survival
- BUT they did see significant benefit or the sever chemotherapy effects of neutropenia
- Another phase II trial in which nondiabetic patients with metastatic breast cancer were randomly assigned to receive the investigator’s choice of chemotherapy in combination with metformin 850 mg every 12 h or placebo
- No significant effects were seen on progression-free survival, response rate, or overall survival
- The article talked about how experimental models showed there should be an effect like seen in mice models. These studies though were not able to show a tangible difference.
My thoughts?
It’s clearly not clear. Studies are conflicting. These human blinded randomized trials didn’t show an improvement. But you also need to look at the trials. These trials were in nondiabetic women. What was their HBA1c? Are they totally not diabetic? Are they mildly elevated, but not to the diabetic level? Some of the positive studies I have seen for metformin and chemo were specifically in patients who were HER2 positive. These patients in these studies were negative.
Or is it a red herring? Sometimes what we see as promising in the lab does not pan out to be anything when done in real life.
Or is it worth trying because if it doesn’t cause harm, why not? And when I say this it depends on what your labs are. I think you need to look at YOU. What is your resting blood sugar? HbA1C? If it isn’t borderline high, I don’t think I would encourage this.