A vaccination made using a patient\'s own cells triggers tumor eradication in nearly 20 percent of those with one type of breast cancer, U.S. researchers said. Study leader Dr. Brian Czerniecki -- surgical director of the Rena Rowan Breast Center at the University of Pennsylvania and surgical director of the immunotherapy program for the Abramson Cancer Center -- said more than 85 percent of patients with ductal carcinoma in situ appear to have a sustained immune response after vaccination. Czerniecki and colleagues at the Perelman School of Medicine at the University of Pennsylvania enrolled 27 women with HER2-positive ductal carcinoma in situ and isolated specialized white cells from the patients\' blood using, standard techniques similar to the blood donation. The researchers then activated the dendritic cells, which are key regulators of the immune system, and primed them with small pieces of the HER2/neu protein. Each patient received four shots, one week apart, of their personalized anti-HER2 vaccine -- and patients had surgery two weeks later to remove any remaining disease, which is standard care for ductal carcinoma in situ patients. The study, published in the Journal of Immunotherapy, compared pre-vaccination biopsy samples with post-vaccination surgical samples and found five patients had no disease visible, indicating their immune system had wiped out the tumor. Of the remaining 22 patients, HER2 expression was eliminated in 11 patients and reduced by 20 percent or more in another two, the study said. \"We are continuing to see this pattern in our second, ongoing trial,\" Czerniecki added.