Anti-Cancer Immune Reaction Induced by Cryo-Ablation Therapy for Unresectable Advanced Liver Tumor

Abstract

Background: Cryogenic treatment sometimes stimulates the immune system by releasing intracellular antigens. We evaluated anti-tumor immune response after cryotherapy by analyzing alterations in serum cytokine levels. Methods: Percutaneous cryosurgery was performed in 13 patients with unresectable advanced tumors. The size of the ice ball was confirmed by intraoperative ultrasound 15 minutes freezing to make a 3-cm ice ball. The therapy was performed for three freeze/thaw cycles per a tumor per a treatment and was continued eight times for once a week. Evaluation of serum factors was done before and after ablation therapy, and serum tumor markers were measured after every four treatments. Tumors were evaluated by abdominal computed tomography after eight treatments. Serum levels of interleukin (IL) -4, -6, and -10, tumor necrosis factor (TNF)-alpha, and interferon (IFN)-gamma were measured by ELISA. The Th1/Th2 ratio was estimated from the IFN-gamma/IL-4 ratio. Results: In five cases, tumor necrosis was identified not only in the treated area but also away from the treated area, and then these cases belonged to immune reaction (IR) group. In other cases, just local effect was noted (LE), and then levels of serum factors were compared with those in IR. Serum levels of AA and CRP were increased in both the IR and LE groups after the third treatment, and that of IL-6 paralleled CRP increases. No differences in the level of serum IL-2 was observed after treatment in any of the patients. The serum level of IL-10 was low in three patients in the IR group and in one patient in the LE, but it group tended to increase with the number of treatments. In contrast, the level of TNF-alpha was increased in the IR group but showed no remarkable changes in the LE group. The Th1/Th2 ratio was increased in the IR group, compared to that in the LE group. To evaluate the clinical significance of these alterations in serum cytokines, pretreatment levels, maximum levels in response to therapy, and the number of treatments necessary to induce maximum levels were compared between the two groups. Pretreatment levels of IL-10 in the LE group were significantly greater than those in the IR group (p=0.0071), and the maximum value (67.9±6.3 pg/mL) was greater than that for the IR group (58.4±8.1 pg/mL), but no significant difference was found between the two groups. In contrast, both pretreatment levels and maximum levels in response to treatment of TNF-alpha were significantly greater in the IR group than in the LE group. The maximum Th1/Th2 ratio was significantly greater in the IR group than in the LE group, despite the factor that pretreatment levels and treatment times to induce maximum levels were similar between the two groups. Conclusion: It might be possible to evaluate the appearance of immune responses to cryosurgery by monitoring serum cytokine levels.