Metformin for HNSCC

Hi all,
I have been reading studies showing that diabetes type 2 drug METFORMIN may have some impact on shrinking tumors and increasing over all survival. I am wondering if anyone here is taking/has taken this drug and has any comments. Do you think its helping? Have you had any significant side effects? I am also trying to get a handle on the correct dosage for non-diabetics, if anyone has an idea.... Thanks!