Adding the drug pertuzumab to trastuzumab and docetaxel chemotherapy extended survival in women with HER2-positive breast cancer, U.S. researchers say. Senior researcher Dr. Jose Baselga of the Harvard Medical School, associate director of the Massachusetts General Hospital Cancer Center and chief of hematology/oncology at Massachusetts General Hospital, and colleagues conducted an international phase three, double-blind, randomized trial, known as CLEOPATRA for CLinical Evaluation Of Pertuzumab And TRAstuzumab. The findings represent a significant advance in the treatment of this advanced breast cancer, Baselga said. "This is huge. It is very uncommon to have a clinical trial show this level of improvement in progression-free survival," Baselga said in a statement. "Most metastatic patients with HER2-positive breast cancer eventually stop responding to trastuzumab, so the fact that we now have an agent that can be added to current treatment to delay progression is very exciting. With the advent of trastuzumab and now pertuzumab, we have come a very long way in treating a type of breast cancer that once had a very poor prognosis." The researchers randomly assigned 808 patients to receive trastuzumab and docetaxel chemotherapy with pertuzumab or placebo. The study, published in the New England Journal of Medicine, found progression-free survival time was 18.5 months for patients who received pertuzumab compared with 12.4 months for patients who received placebo -- a 38 percent reduction in risk for progression. The findings were also presented at the Cancer Therapy & Research Center-American Association for Cancer Research San Antonio Breast Cancer Symposium.