OBJECTIVETo develop a novel thermal treatment modality against metastatic tumor, and to verify the hypothesis that the extent of tumor angiogenesis damage and tumor cell necrosis, accompanied with immune suppression cells relief is deterministic to enhance therapeutic effect in the thermal treatment.

METHODSThe thermal treatment system was developed in our laboratory. The treatment including hyperthermia and alternate treatment, were locally applied to 4T1 murine mammary carcinoma. The extent of tumor necrosis was examined. Further investigations were performed to study the changes of MDSCs in peripheral blood and spleen.

RESULTSThe alternate treatment caused more damage to tumor microvasculature and tumor cell necrosis. Immunosuppression cells significantly reduced in peripheral blood and spleen. Moreover, it highly increased the survival rate of tumor-bearing mice.

CONCLUSIONSThe greatest destruction of primary tumor induced by the alternate treatment led to a relief of immune suppression in tumor bearing mice, and significantly increased therapeutic effect, especially for metastatic tumor.