Background: Patients with very high-risk prostate cancer (VHR-PC) features experience worse outcome after radical prostatectomy. This study was designed to assess biochemical failure and toxicity of adjuvant dendritic cells vaccine (DCV) in prostate cancer patients who are at greatest risk for cancer progression. Methods: Twenty patients with pathological stage pT2 - pT3b and Gleason score 7B-10, pN0, pN+ or pNx were enrolled into the approved study DC-005. The primary end point was clinical failure. Ten patients were tested for disseminated tumor cells (DTCs) to the bone marrow before inclusion to the study. Three patients out of 10 patients had positive DTCs detection in bone marrow. The mean age of the cohort was 63 years (SD 6.9 years), and three patients had postsurgical pN1 status. Eighteen patients had two or more high-risk factors (ISUP grade 5, T3- stage and or PSA > 20 ng/mL). Autologous dendritic cells were transfected with mRNA for hTERT, survivin and tumor mRNA. The DCV product was applied intradermally after curative intended surgery once per week the first months, then once per months the first year, thereafter every 3 months for two years or until biochemical progression (PSA relapse cut-off ≥ 0.3). Results: After 5 years follow-up (FU) 62% (12/20 patients) had not biochemically progressed and with a median FU of 69 months all patients included in the study are alive. Five patients were treated with salvage and one patient with adjuvant radiation treatment, three patients received limited ADT, and three patients are on first line ADT, none of those eight patients have experienced castration resistant prostate cancer. The toxicity was mild with no serious adverse event related to DCV. Conclusions: Adjuvant DCV mitigates the time to biochemical progression. These results appear favorably compared to historical controls in VHR-PC. The clinical outcomes of this study warrants a future enlarged clinical trial. Clinical trial information: NCT01197625