AB085. Immune therapy: new option for prostate cancer

Objective: Immunotherapy has emerged as another treatment modality in cancer. Appropriate combination of tumor mass reduction and neutralization of tumor-induced immunosuppression might set the right conditions for the induction of anti-tumor immune response. Besides the direct cytotoxic effect on the tumor cells, chemotherapy also decreases the immunosuppressive mechanisms induced by the tumor and allows for the priming of anti-tumor immunity. We performed an open label, single arm clinical trial in patients with metastatic castrate resistant prostate cancer (mCRPC) eligible for docetaxel treatment using autologous mature dendritic cells pulsed with killed LNCap prostate cancer cell line, DCVAC/PCa.

Methods: Eligible patients had progressive mCRPC despite androgen deprivation. DCVAC/PCa treatment consisted of, on average ten doses of 1×10⁷ dendritic cells injected s.c. Patients then started docetaxel (75 mg/m²) and prednisone (5 mg twice daily) treatment administered every 3-week and DCVAC/PCa was given every 6-week up to a maximum number of doses manufactured from one leukapheresis. The primary end point was safety, the secondary end-point immune response. Overall survival (OS) followed as a part of safety evaluation was compared to the predicted OS according to Halabi and MSKCC nomograms.

Results: Until June 2015, data from 21 patients were evaluated and approximately 230 doses of ACI have been administered so far. The mean age at the start of immunotherapy was 68 years, median PSA 67 ng/mL. 67% patients had GS ≥8. No serious DCVAC/PCa-related adverse events have been reported. There were no clinical or laboratory signs of autoimmunity. Median OS was 19 months (95% CI: 14.69-23.31) while the predicted median OS was 12 months (95% CI: 11.19-12.81).

Conclusions: In patients with mCRPC, the alternate administration of DCVAC/PCa cancer immunotherapy and docetaxel results in the stabilization of the disease progression and longer than expected survival. Chemotherapy does not preclude the induction of tumor specific T cells.

Keywords: Immune therapy; prostate cancer; dendritic cell