The Food and Drug Administration (FDA) has expanded the approved use of the drug ado-trastuzumab emtansine (Kadcyla) to treat some women with HER2-positive breast cancer. Ado-trastuzumab, also called T-DM1, was initially approved by FDA more than 6 years ago to treat women with metastatic HER2-positive breast cancer. Under the expanded approval, it can now be used when the cancer is far less advanced: as a post-surgical, or adjuvant, treatment in women with early-stage HER2-positive breast cancer. However, to be eligible to receive the drug under this newly approved use, women must first have undergone presurgical, or neoadjuvant, therapy to shrink their tumors and still have some signs of remaining invasive cancer, called residual cancer, in the breast or nearby lymph nodes. The new approval, announced on May 3, is based on findings from a large clinical trial called KATHERINE that compared T-DM1 with trastuzumab (Herceptin) as an adjuvant treatment. In the trial, women treated with T-DM1 had a 50% reduced risk of their cancer returning or death than women treated with trastuzumab. Side effects, including serious side effects, were more frequent in women treated with T-DM1. As a result, more women taking T-DM1 (29%) did not complete the full course of the adjuvant treatment than women taking trastuzumab (19%). But many of these women did not have to stop taking the drug until they were near the end of their adjuvant treatment period, explained the study’s lead investigator, Charles Geyer, Jr., M.D., of the Virginia Commonwealth University Massey Cancer Center. In general, Dr. Geyer said, “the majority of women tolerated the drug reasonably well.” The trial results, and the subsequent FDA approval, have already had an important impact on patient care, Dr. Geyer said. “T-DM1 has now become the standard of care for women with HER2-positive breast cancer and residual invasive cancer following neoadjuvant therapy,” he said.