Follow-up evaluation of a phase II prostate cancer vaccine trial

Abstract

BACKGROUND: A phase II trial, involving infusions of autologous dendritic cells (DC) and two human histocompatibility antigen (HLA-A2)-specific prostate-specific membrane antigen (PSMA) peptides, was recently completed. Thirty percent of the participants, including subjects with hormone-refractory metastastic disease, and those with suspected local recurrence of prostate cancer, were identified as clinical responders. This report describes the follow-up evaluation of 19 responders in the two study groups. METHODS: After conclusion of the study, study participants were subjected to follow-up evaluations at 6-8-week intervals. Each responder was reevaluated for response status, and duration of response was determined. RESULTS: Subjects were observed for an average of 291 days (metastastic group, group A-2) and 557 days (local recurrence group, group B), which included the treatment and follow-up periods. The average duration of response was 149 days for group A-2, and 187 days for group B. A majority of responders (11/19; 58%) were still responsive at the end of the current follow-up. CONCLUSIONS: The responses observed may be significant and relatively durable. This study suggests that DC-based cancer vaccines in the future may provide an additional therapy for advanced prostate cancer.