For women with metastatic, HER2-positive breast cancer, the amount of HER2 on their tumor might determine how much they benefit from a drug called trastuzumab emtansine (T-DM1), according to data from a subanalysis of the phase III clinical trial that led the U.S. Food and Drug Administration to approve the drug on Feb. 22, 2013. These findings were presented by José Baselga, M.D., Ph.D., physician-in-chief at Memorial Sloan-Kettering Cancer Center in New York, N.Y., at the AACR Annual Meeting 2013, held in Washington, D.C., April 6-10.