"With this vaccine, we can clearly generate immune responses that lead to clinical responses in some patients," said lead researcher James Gulley, M.D., Ph.D., director and deputy chief of the clinical trials group at the Laboratory of Tumor Immunology and Biology at the National Cancer Institute.
Gulley and colleagues enrolled 26 patients and assigned them to monthly vaccinations with the PANVAC vaccine, which contains transgenes for MUC-1, CEA and three T cell costimulatory molecules.
These patients were already heavily pretreated, with 21 of them receiving at least three prior chemotherapy regimens.
Among the 12 patients with breast cancer, median time to progression was 2.5 months and median overall survival was 13.7 months. Four patients had stable disease.
For the 14 patients with ovarian cancer, median time to progression was two months and median overall survival was 15 months.
Following treatment, mild injection-site reactions were the most common side effect.
According to Gulley, interest in cancer vaccines is increasing and more study is needed to determine which vaccines will benefit which patients. "The sustained benefit seen in some patients in this study underscores the potential for therapeutic vaccines to impact clinical outcomes without toxicity," he said. "However, more studies in the appropriate patient populations are required to adequately assess efficacy."
The study was funded by the National Cancer Institute.