Aromatase inhibitors, a type of hormone therapy used to treat advanced breast cancer in postmenopausal women, result in a small but significant increase in overall survival when compared to other hormone treatments, according to a new systematic review of studies. In addition, aromatase inhibitors -- drugs known as Arimidex, Aromasin and Femara -- are less likely to cause blood clots and vaginal bleeding than other hormone treatments, said review co-author Judith Bliss of the Institute of Cancer Research in London. The review analyzed 30 studies involving the treatment of advanced breast cancer, encompassing more than 10,000 postmenopausal women. Bliss and colleagues were surprised at how few of the reviewed studies presented data on overall survival for women taking aromatase inhibitors.