Mechanism of heightened tumor immunity induced by cryosurgery.

Sarcoma-bearing mice treated with cryosurgery demonstrated significantly greater tumor immunity (as measured by lymphocytoxicity assays) than untreated tumor-bearing mice (p less than .001). However, cryosurgically treated mice did not show greater cytotoxicity than tumor-bearing and tumor-amputated mice which were treated with frozen exogenous tumor antigen. These results suggested that the mechanism by which cryosurgery stimulates systemic tumor immunity is through the release of antigen from the neoplasm. Thus, tumor-bearing mice treated with cryosurgery in these experiments underwent definitive ablative therapy while at the same time they received active tumor immunotherapy.