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Cryotherapy for Hepatic Colorectal Carcinoma Metastases

Approximately 20 percent of the nearly 160,000 Americans diagnosed with colorectal cancer each year will have liver metastases at presentation. An additional 20 percent to 30 percent will develop liver metastases subsequent to treatment of their primary cancer. Systemic chemotherapy is widely employed for unresectable disease and is associated with only a 20-40 percent response rate with little impact on long-term survival. As a result, investigators are currently evaluating both regional and systemic treatments in the hope of improving both survival and quality of life

In spite of the poor response of colorectal liver metastases to systemic therapy, regional hepatic arterial infusional (HAI) chemotherapy is associated with response rates of nearly 85 percent in untreated patients (no previous systemic 5-FU) and 52 percent in previously treated patients (received 5-FU within the past 6 months).1 Complete eradication of hepatic metastases is rarely evident, however, and after stopping therapy, tumor progression in the liver is frequently observed. The inability to achieve a complete response with regional chemotherapy alone, even with prolonged treatment, is part of the problem. Regional chemotherapy is limited by liver toxicity and biliary sclerosis during long-term use.

Cryosurgery has been available for many years but only recently has been applied to the ablation of liver tumors in situ. This is primarily due to improvements in cryotechnology as well as the availability of high-resolution intraoperative ultrasound. The technique involves operative placement of a metal probe into the center of a tumor. Liquid nitrogen or argon gas flows through this freezing probe and initiates the creation of an ice ball starting in the tumor's center and gradually expanding outward. The formation of the spherical ice ball is monitored by intraoperative ultrasonography and is complete when the ice ball is 1 centimeter beyond the tumor. In this manner, tumor tissue is destroyed with minimal destruction of normal liver tissue.

There are limiting factors to cryotherapy of hepatic metastases. Metastatic tumors more than 5 centimeters in diameter or in close proximity to major vascular structures or bile ducts are difficult to completely freeze safely. Another limiting factor is the number of hepatic metastases. As many as eight small metastases can be frozen, but in patients with four or more tumors it is quite likely that immeasurable smaller hepatic metastases are present. Under these circumstances, it is unlikely that cryotherapy alone will result in long-term disease control unless other therapies such as regional HAI chemo-therapy also are used.