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BACKGROUND A phase II trial was conducted to assess the efficacy of infusions of dendritic cells (DC) and two HLA‐A2‐specific prostate‐specific membrane antigen (PSMA) peptides (PSM‐P1 and ‐P2). This report describes the evaluation of 37 subjects admitted with presumed local recurrence of prostate cancer after primary treatment failure. METHODS All subjects received six infusions of DC pulsed with PSM‐P1 and ‐P2 at 6‐week intervals. Clinical monitoring was conducted pre‐, during, and post‐phase II study. Data included: complete blood count, bone and total alkaline phosphatase, prostate markers, physical examination, performance status, bone scan, ProstaScint® scan, and chest X‐ray, as well as other assays to monitor cellular and humoral immune responses. RESULTS One complete and 10 partial responders were identified from this group based on National Prostate Cancer Project criteria, or on a 50% reduction of prostate‐specific antigen (PSA), or on a significant resolution in lesions (biopsy‐proven when possible) on ProstaScint® scan. CONCLUSIONS About 30% of study participants in this group showed a positive response at the conclusion of the trial. This study suggests that DC‐based cancer vaccines may provide an alternative therapy for prostate cancer patients whose primary treatment failed. Prostate 39:54–59, 1999. © 1999 Wiley‐Liss, Inc.

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.

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