Cryosurgery for the treatment of cancer.

Cryosurgery is that branch of cryobiology and surgery which deals with the therapeutic application of cold at profoundly low temperatures (those below 0 degrees C) for the purpose of destroying tissues in selected target sites. The freezing process induces coagulation necrosis and is confined to the tissues within the region of the probe application and the ice ball. The degree and extent of tissue destruction depend largely on the size of the ice ball and the temperatures within it. Various types of equipment and probes are commercially available for cryosurgery, but it was only after the development of reliable, versatile cryosurgical systems cooled by liquid nitrogen that numerous applications for cryosurgery were proposed, including therapy for cancer. In the treatment of cancer, clinical success with cryosurgery has led to the more wide-spread application of this modality in selected patients. Cryosurgery has been used for readily accessible lesions in specific anatomic areas, most frequently the skin and oral cavity. It is an attractive alternative to extirpative surgery, particularly in the head and neck, where removal of large portions of the mandible or maxilla are often required to control cancer. Therefore, it is not surprising that many of the pioneering efforts in the treatment of cancer have been conducted by otorhinolaryngologists. The full theoretic potential of cryotherapy was somewhat slow to be realized because many early endeavors were directed toward palliation, especially of accessible tumors of the skin and oral cavity, after failure of tumor control by radiation or surgery or both. This limited application during the early period of evaluation reflected a naturally timorous course that was taken by those who introduced the new modality into clinical practice. This period paralleled the development of new apparatus, early clinical trials, and the assessment of the clinical potential of cryosurgery in patients with incurable cancer--those whose conditions were deemed hopeless. Today, cryosurgery is selectively applied for the treatment of patients with tumors involving structures such as bone, oropharyngeal mucosa, temporal bone, skin, brain, retina, prostate, uterine cervix, and tracheobronchial tree. Although general guidelines for the application of cryosurgery to cancer can be gleaned from various clinical reports, the optimal conditions of freezing have not been specially defined. Animal experiments are necessary to study the variables methodically and in detail. The temporal and physical conditions for cryogenic necrosis of cancer require delineation so that cell death can be predictably and consistently reproduced. This is the thrust of this paper.