PERIVASCULAR AND INTRALESIONAL TISSUE NECROSIS AFTER HEPATIC CRYOABLATION - RESULTS IN A PORCINE MODEL

Background. Cryosurgical ablation of malignant hepatic tumors is being increasingly used for definitive treatment of metastatic colorectal a nd primary hepatic tumors. The lack of tumor necrosis near vessels tha t results from inadequate freezing may contribute to local recurrence and thus limit the applications of this therapy. This study was design ed to determine whether single-freeze cryoablation could cause necrosi s of both the perivascular and intralesional hepatic parenchyma. Metho ds. Ten pigs were treated with one 15-minute cycle of cryoablation. Fi ve additional animals were treated with overlapping cryolesions to sim ulate a double freeze. After 24 hours, animals underwent reoperation w ith portal vein cannulation, and infusion of formalin. Serial sectioni ng and hematoxylin and eosin staining of cryolesions were performed. R esults. Complete cell death was visualized within all cryolesions. The re teas no difference between once- or twice-frozen tissue. Vessels wi thin or adjacent to cryolesions showed necrosis of hepatic tissue np t o the vessel wall No sections revealed incomplete necrosis of perivasc ular hepatic parenchyma. Conclusions. Single-freeze cryoablation resul ts in necrosis of intralesional hepatic parenchyma without added benef it from repeat freezing. Complete necrosis of the perivascular tissue suggests that cryosurgical ablation can effectively cause necrosis imm ediately adjacent to vessels without concerns of incomplete ablation r esulting from the heat sink effect.