Hepatic cryotherapy has now been used in over 2,000 patients with liver cancer identified by a recent world survey of 72 users. While safety is good with a total of 33 deaths, 18% of these were due to cryoshock. The majority of s es were in USA/Canada - 55, Europe - 10, and Asia/Australia - 5. There is published literature on 867 patients, mortality 1.6%, significant hemorrhage 3.9%. Survival data is more limited - one small study reported 5-year survival of 78% in colorectal cancer, but median survival of 26 months has been reported in two larger studies, including our own. Our own analysis of prognostic factors in 195 patients identified the following as independently associated with a good outcome: low pre-op CEA, normalization of CEA, small lesion diameter (< 3 cm), absence of extra hepatic disease, complete cryo treatment, synchronous development of liver metastases and good/moderate differentiation of the primary tumor. Echogenicity of lesions was also prognostic.
For hepatoma, a total of 200 patients with 5-year survival of up to 64% for lesions < 5 cm has been reported.
Cryotherapy can also be an important adjunct to liver resection. We now have experience of cryotherapy to the other lobe of the liver, at the time of resection in 20 patients, with a good fall in CEA and survival at 1 2 years of 88 and 60% and median survival of 32 months. Resection edge cryotherapy for involved or close resection margins in 44 patients has been associated with low recurrence rates. Only 5 have developed edge recurrence.
Our animal research program has included work on a rat model of cryshock which has clearly linked Cytokine (IL6, TNF) release with the volume of cryo destruction and serum AST. Pharmacological attempts to modify cryoshock are in progress.