Laser-induced thermotherapy - Intra- and extralesionary recurrence after incomplete destruction of experimental liver metastasis

Purpose: The aim of this study was to determine the energy (J/mm(3) tumor v olume) and temperature required for a complete laser-induced thermotherapy (LITT) of experimental liver tumors, and to find out causes and areas of lo cal recurrence followed by incomplete treatment. Methods: In VX-2 tumor-bearing rabbits LITT was performed using neodymium:y ttrium-aluminum-garnet (Nd:YAG) laser (1064 nm) with a diffuser-tip applica tor and a temperature feedback system. The animals were randomized into fou r groups (n=20) that differed in the target temperature at the tumor border as follows: 45 degreesC, 50 degreesC, 55 degreesC and 60 degreesC. The tar get temperature was held for 10 min constant. Histologic examination (hemat oxylin and eosin [H&E], nicotinamide adenine dinucleotide phosphate [NADPH] -dehydrogenase) was performed at 0 h, 24 h, 96 h, and 14 days aver LITT. Results: The pretreatment tumor volume of 2191 +/- 61 mm(3) was the same fo r all groups (p>0.05). Energy up to target temperature and total energy req uired, lesion size, and the rate of incomplete tumor ablation (recurrences) are listed below ((a)p<0.05, Kruskal-Wallis test). Histologically, two for ms of local recurrences could be differentiated intralesionary and extrales ionary. Conclusions: To achieve complete in situ ablation under the given condition s, it is necessary to apply laser energy of 3 J/mm(3) tumor volume. A minim um temperature of 60<degrees>C on the tumor border presumed an application of 10 min. Recurrence was found outside the coagulation zone (extralesionar y) and in high vascularized areas within the coagulation zone (intralesiona ry).