From: Proceedings 10th World Congress of Cryosurgery
Maintenance of freezing increases the degree of cryodamage in cancer cells

November 1998
WK Berger
1. Physiol. Institute, University of Saarland/Homburg, Germany

According to the results of experimental cryosurgery on skin cells, the time of exposing cells to low temperatures plays an important role for the degree of cryodamage (Gage, et. al., 1985). Using neuroblastoma cells, I have studied the effect of the prolonged exposure to low temperatures on cancer cells. Cells in suspension were frozen in a shallow experimental chamber between 2 cover glasses and were cooled to temperatures between 1OC and -50C by a Peltier element. Live/dead cell staining with fluorescent dyes and Epifluorescence optics were used to evaluate the degree of cryodamage. The number of surviving cells decreased with falling temperatures. At each temperature level, the degree of cryodamage was further increased by holding the temperature for 5 minutes at the low level. The effect was maximal between -20C and -30C; i.e., at temperatures which are found in the periphery of tissue frozen by a cryoprobe. The effects of prolonged exposure to low temperatures on tissue damage were in most temperature ranges comparable to those resulting from repeated freeze-thaw cycles. It appears that for the treatment of multiple metastases in the liver, one freezing period with 5 minutes of holding may replace the time-consuming 2 freeze-thaw cycles in order gain time for the cryosurgical treatment of additional tumors.

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