Interstitial
laser coagulation as a means of destructing hepatic
metastases was investigated. Colon
carcinoma CC531 was implanted in the liver of 42 Wag/Rij rats; 20 days later,
tumors (5.5 +/- 0.2 mm) were exposed to 1,064 nm
Nd:YAG laser light at 4 W/cm and either 600, 1,200, 2,400, 3,400, or 4,800 J/cm from a 0.5 cm
Helioseal coated cylindrical diffuser. Temperature and fluence rate were measured at the
tumor boundary. Lesions were studied on day 2 and 36 posttreatment by light microscopy.
Tumor proliferative activity was assessed by
bromodeoxyuridine incorporation. Liver damage and function were determined by serum liver
enzymes and
antipyrine clearance. Fluence rate increased during
laser treatment up to 170%; mean temperature increased logarithmically up to 69.7 degrees C. Short-term light microscopy showed coagulation
necrosis of 7-11 mm without charring. Lesion size and liver
enzymes increased logarithmically with
laser energy applied. No deterioration in liver function was found. At 4,800 J/cm complete
tumor remission occurred in three of four animals. This study shows the ability of interstitial
laser coagulation to produce selective destruction of colonic
tumor within the liver.