Radiofrequency (RF) ablation is a minimally invasive technique routinely applied for the treatment of primary and secondary liver tumors. It induces cell death by thermal coagulative necrosis of tumor tissues, whereas cellular metabolism can still take place in a transition zone surrounding the necrotic area. An increase in heat shock protein expression occurs shortly after treatment, suggesting that the induction of activating signals may stimulate the host immune system. In addition, various effects on immune effectors have also been observed, including stimulation of tumor-directed T lymphocytes. Here, we prospectively assessed the activation of tumor antigen-specific antibodies, as well as antigen-specific CD4(+) and CD8(+) T cells in patients suffering from primary or secondary malignancies and treated by RF ablation with or without concomitant chemotherapy. An increase of antibodies (in 4 patients of 49), CD4(+) T cells or CD8(+) T cells (in 2 patients of 49) could be detected several weeks to months following intervention. These findings suggest that in addition to the local control of tumor growth, RF ablation can provide the appropriate conditions for activating tumor-antigen specific immune responses.
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