Requisites for successful cryogenic surgery of cancer.

In three murine tumor-host systems, tumors were frozen to a cryolesion of standard size visually extending beyond the gross tumor margins into normal adjacent tissues, an approach commonly used in clinical cryosurgery. The effects of varying probe-tip surface area, tip temperature, and number of freezes were evaluated in terms of temperature changes within the frozen tissues and effectiveness of tumor control. Wide ranges of tissue temperature change were produced by varying these conditions, even though the visual cryolesion was constant. Repeated freezing increased the cryolesion progression rate and improved cure rate. With either size probe tip, lower tip temperature produced an increased depth of central tumor temperature and increased cure rates. The probe with a relatively large tip-to-tumor contact area produced better tumor control at either temperature with economy of effort.