Roche breast cancer drug extends overall survival ZURICH (Reuters) - Swiss pharma group Roche's drug Perjeta significantly extended the lives of women with an aggressive and incurable form of breast cancer compared to a placebo, according to new data from a late-stage study presented on Saturday. The detailed data presented at the San Antonio Breast Cancer Symposium found that the risk of death was reduced by 34 percent in women treated with a combination treatment of the drugs Perjeta and Herceptin plus chemotherapy compared to women treated with Herceptin, chemotherapy and a placebo, Roche said. Roche is hoping that the Perjeta combination will become the standard treatment for women with a form of cancer known as HER2-positive, which makes up about a quarter of all breast cancers and has no cure. At the time of the analysis, median overall survival had not yet been reached in people receiving the Perjeta combination, as more than half of these people continued to survive, Roche said. Median overall survival was more than three years for people who received Herceptin and chemotherapy, Roche said, adding no new safety signals had been observed in the phase III study. "This treatment combination with Perjeta is the first to have significantly extended survival compared to Herceptin and chemotherapy in people with previously untreated HER2-positive metastatic breast cancer," Roche's Chief Medical Officer Hal Barron said in the statement. Breast cancer is the most common cancer among women worldwide, with about 1.4 million new cases diagnosed each year and more than 450,000 women dying of the disease annually, according to the World Health Organisation. Perjeta, also known as pertuzumab, is a personalized medicine that targets a protein found in high quantities on the outside of cancer cells in HER2-positive cancers. It was granted approval by U.S. health regulators in June. Roche is awaiting a decision from European regulators. Vontobel analyst Andrew Weiss forecasts peak sales of 2 billion Swiss francs ($2.15 billion) for the drug. Roche is also developing an "armed antibody" known as TDM-1 as a treatment for HER2-positive breast cancer. TDM-1 combines Herceptin with a derivative of a powerful type of chemotherapy and is designed to reduce unpleasant side effects. ($1 = 0.9313 Swiss francs) Reporting by Silke Koltrowitz and Caroline Copley; Editing by Paul Tait