Changes in peripheral blood T-cell balance after percutaneous tumor ablation

PURPOSE: To evaluate the changes in T-cell balance in peripheral blood following percutaneous tumor ablation. MATERIAL AND METHODS: Patients underwent thermal ablation including radiofrequency (n = 9) and microwave ablation (n = 5), or cryoablation (n = 5). Target tumors were located in the lung (n = 7), soft tissue (n = 5), liver (n = 4), and bone (n = 3). Patient peripheral blood samples were collected before and within 14 days after ablation. Peripheral blood populations of cytotoxic T-cells (CTL), type-1 (T(h)1) and type-2 helper T-cells (T(h)2), and regulatory T-cells (T(reg)) were measured using flow cytometry. Changes in CTL/T(reg) and T(h)1/T(h)2 ratios before and after ablation therapy were compared using paired t-tests. RESULTS: Peripheral blood CTL population (27.5 ± 2.1% to 30.2 ± 2.5%, p < .03) and CTL/T(reg) ratios (18.8 ± 3.7% to 21.6 ± 3.6%, p < .05) increased significantly after ablation. Although a significant increase in CTL/T(reg) ratios was found after heat-based ablation (18.0 ± 4.4% to 21.6 ± 4.7%, p < .02), it remained unchanged after cryoablation (21.0 ± 7.0% to 21.5 ± 4.3%, p = .92). T(h)1/T(h)2 ratio (13.7 ± 3.0% to 17.2 ± 3.5%, p = .12) remained unchanged after ablation. CONCLUSION: Ablation therapy alters the T-cell balance by increasing the systemic CTL/T(reg,) ratio. Heat-based ablation might be a more effective approach than cryoablation to enhance systemic anti-tumor immunity.