OBJECTIVETo assess the anti-tumor immune response to percutaneous cryoablation in patients with local prostate cancer.

METHODSWe treated 10 patients with local prostate cancer by percutaneous cryoablation, collected the blood samples before and 2 weeks after the treatment and isolated peripheral blood mononuclear cells (PBMCs). Protein lysates were made by biopsy from autologous prostate cancer or non-cancer tissues. The levels of serum TNF-alpha, IFN-gamma, IL4 and IL-10 were determined by enzyme-linked immunosorbent assay (ELISA) and the Th1/Th2 ratio was calculated by the IFN-gamma/IL-4 ratio. The number of IFN-gamma + T cells under the stimulation of different protein lysates was counted by enzyme link immunol spot (ELISPOT). And the cytolytic activity of cytotoxic T lymphocytes (CTL) was detected by LDH assay.

RESULTSCompared with pre-treatment, the levels of TNF-alpha and IFN-gamma, the Th1/ Th2 ratio and the number of IFN-gamma + T cells induced by tumor protein lysates in PBMCs were increased significantly after cryosurgery (P < 0.01), while the levels of IL4 and IL-10 decreased slightly, and the non-tumor protein lysates induced no obvious changes in the number of IFN-gamma T cells. The cytolytic activity of cytotoxic T lymphocytes against human prostate cancer cells LNCaP was markedly increased, but not that against renal cancer cells GRC-1. One case of recurrence was found during the 3-6 months follow-up.

CONCLUSIONPercutaneous cryoablation for prostate cancer could induce a tumor-specific immune response.