Metformin: an old drug with new potential.

Metformin is the most commonly prescribed antidiabetic oral agent. It has also been used off-label for polycystic ovarian syndrome, steatohepatitis, and HIV-associated metabolic abnormalities. However, this oldie is a newbie for the oncologist. Population studies have suggested that metformin decreased the incidence and mortality rates of cancer in diabetic patients. With better understanding of its mechanisms of antitumor activity, metformin may become a new drug for cancer in combination with chemotherapy or targeted therapy.