Immunological evaluation of personalized peptide vaccination for metastatic breast cancer patients with triple-negative types.

e13046 Background: To develop cancer vaccine, we investigated immune responses of the patients (pts) with metastatic breast cancer (MBC) with triple negative (TN) types to personalized peptide vaccine (PPV). Methods: Thirty-four pts including 8 TN-MBC were enrolled a phase II study of PPV. A maximum of four HLA-class IA (A2, A3s, A24, A26)-matched peptides showing higher antigen-specific IgG responses were administered. Levels of IgG reactive to each of the 31 peptides in the pre- and post-treatment plasma at every 6 times of vaccination were measured using LUMNEX system. Peptide-specific CTL responses were examined by INF-g ELISPOT. Results: All 34 pts had significant pre-existing humoral immunity, whereas only 13 of 31 patients, including 3 of 6 TN cases, showed pre-existing cellular immunity. Thirty-one of 34 pts, including 6 TN cases, achieved more than one cycle (6 times) of vaccination. The augmentation of the IgG responses specific to at least one of the vaccinated peptides was observed in 18 of 31...