An example of a possible specialized application of metformin in cancer treatment. An example of a possible specialized application of metformin in cancer treatment. Many contexts in which metformin may have a use in cancer treatment have been proposed. One example involves use with androgen deprivation therapy in prostate cancer. As discussed in the text, androgen deprivation has obvious benefit for men with metastatic prostate cancer, but this is temporary, and is associated with adverse effects related to androgen deficiency–induced hyperinsulinemia, including increased cardiovascular disease risk. As insulin may directly stimulate neoplastic growth of certain prostate cancers, or upregulate intratumoral testosterone synthesis, the hyperinsulinism of androgen deprivation may also contribute to progression to castration-resistant disease. If ongoing research shows that metformin attenuates the hyperinsulinemia associated with androgen deprivation, combined androgen deprivation and metformin may improve both tolerability and efficacy. Michael N. Pollak Cancer Discovery 2012;2:778-790 ©2012 by American Association for Cancer Research