As a diabetic who has taken metformin since 2001, I am very interested in following the results of these particular clinical trials.
Because my hormone receptors are "barely positive" and this protocol is being used for hormone negative prevention, I am even more interested.
There are other clinical trials that show a benefit of pairing metformin with or without traditional chemotherapy in a neoadjuvant setting (which means chemo before lumpectomy or mastectomy). In many cases, the tumors are shrinking away completely.
This is the current Canadian clinical trial, which involves administering metformin for a few weeks prior to surgery (without traditional chemo):
Metformin works to reduce the amount of insulin circulating in the body and helps the cells to be more receptive to the insulin required to maintain glucose control. I have read studies that indicate sugar feeds cancer, and too much insulin also feeds cancer cells.
So the fact that metformin would work to prevent cancer makes some sense. Remember that almost half my tumor had "died" prior to surgery. Well, we had doubled my metformin right at my cancer diagnosis because my numbers were running too high. It makes me wonder if the metformin did double duty. There's no way to be sure, unfortunately. But I'll be on this drug probably forever. And unless the clinical trials prove otherwise, I'm hoping that the anti-cancer properties work for me. I think they already did some good work!