In this study we investigate whether the addition of an autologous dendritic cell (DC) based cancer vaccine provokes an immune response in patients with metastatic castration-resistant prostate cancer (mCRPC) treated with docetaxel based chemotherapy.
43 patients were randomized 1:1 to receive up to 10 cycles of docetaxel alone, 75 mg/m2/q3 weeks or in combination with an autologous DC based vaccine. CD14+ monocytes were initially isolated from patients randomized to combinational therapy following a leukapheresis procedure. Harvested cells were incubated with GM-CSF and IL-4 and the resulting immature DCs were further matured using IL-1ß, TNFα, IL-6 and PGE2. mRNA encoding prostate specific antigen, prostatic acid phosphatase, survivin and hTERT was transfected into mature DCs using electroporation. Vaccines were administered intradermally at day 8 and 15 through treatment cycles 1 - 4 and at day 8 only through treatment cycles 5 – 10. Delayed type hypersensitive (DTH) tests were applied. Immune cell composition and antigen specific responses in blood samples were analyzed using flow cytometry and ELISPOT. Prostate cancer clinical trials working group 2 guidelines were followed. Toxicity was graded according to CTCAE version 4.0. Progression free survival (PFS) and disease specific survival (DSS) was calculated using the Kaplan-Meier method.
Baseline mCRPC prognostic factors were equally distributed in the two treatment groups. Median number of treatment cycles was 7. Rates of 50% PSA-responses were 63% vs 38% (p = 0.11) in the docetaxel alone (n = 19) and combinational therapy group (n = 21), respectively. Median PFS and DSS was 5.5 vs 5.7 months (p = 0.62, log-rank) and 24.7 vs 25.1 months (p = 0.70, log-rank). Vaccine induced toxicity was limited to mild local skin reactions and pain. Analysis of chemotherapy induced toxicity, DTH and immune monitoring is currently ongoing and will be presented.
The addition of an autologous DC based cancer vaccine was safe in this study. Survival endpoints were similar in both groups of patients investigated.
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Center for Cancer Immune Therapy and Department of oncology, Herlev University Hospital
All authors have declared no conflicts of interest.