RESUMO
PURPOSE: To investigate synergistic effect of local cryoablation with systemic immunotherapy, the tumor control ability and immunologic responses of combining these two modalities was compared with that of cryoablation, surgical excision, and immunotherapy only group in a tumor re-challenge model. MATERIALS AND METHODS: Preliminary experiments were performed in two stages. The first stage consisted of 36 Balb/c mice with Renca bearing tumors imbedded in the right thigh, and was treated with interleukin-2 (IL-2) and interferon-alpha(IFN-alpha) to evaluate the efficacy of immunotherapy and to determine the adequate dosage. The second stage was performed on 10 mice, to evaluate histological changes and efficacy after cryoablation. The main experiment was performed on 48 mice, divided into 6 groups of control with tumor implantation, excision of tumor, excision combined with immunotherapy, cryoablation of tumor, cryoablation with immunotherapy and control without tumor. After treatment, tumor re-challenge was performed with Renca cell, then the growth pattern was evaluated with physical measurements, and immune response was investigated with fluorescent activated cell sorter and cytotoxicity assay. RESULTS: Preliminary studies on immunologic efficacy revealed that IL-2 and IFN-alpha have a dose dependent inhibition of tumor growth. The main experiment evaluating the efficacy of combination treatment revealed that cryoablation with immunotherapy proved to be most effective in terms of tumor recurrence and tumor growth inhibition, yet the difference was not statistically significant from monotherapy with cryoablation. However, cytotoxicity was significantly increased cryoablation with immunotherapy compared with other groups. CONCLUSIONS: Cryoablation on tumor re-challenge mice model showed advantages with immunotherapy most prominently in cytotoxicity.