Laser-induced thermotherapy: intra- and extralesionary recurrence after incomplete destruction of experimental liver metastasis.
OBJECTIVE
The aim of this study was to determine the energy (J/mm3 tumor volume) and temperature required for a complete laser-induced thermotherapy (LITT) of experimental liver tumors, and to find out causes and areas of local recurrence followed by incomplete treatment.


METHODS
In VX-2 tumor-bearing rabbits LITT was performed using neodymium:yttrium-aluminum-garnet (Nd:YAG) laser (1064 nm) with a diffuser-tip applicator and a temperature feedback system. The animals were randomized into four groups (n = 20) that differed in the target temperature at the tumor border as follows: 45 degrees C, 50 degrees C, 55 degrees C and 60 degrees C. The target temperature was held for 10 min constant. Histologic examination (hematoxylin and eosin [H and E], nicotinamide adenine dinucleotide phosphate [NADPH]-dehydrogenase) was performed at 0 h, 24 h, 96 h, and 14 days after LITT.


RESULTS
The pretreatment tumor volume of 2191 +/- 61 mm3 was the same for all groups (p > 0.05). Energy up to target temperature and total energy required, lesion size, and the rate of incomplete tumor ablation (recurrences) are listed below (ap < 0.05, Kruskal-Wallis test). Histologically, two forms of local recurrences could be differentiated intralesionary and extralesionary.


CONCLUSIONS
To achieve complete in situ ablation under the given conditions, it is necessary to apply laser energy of 3 J/mm3 tumor volume. A minimum temperature of 60 degrees C on the tumor border presumed an application of 10 min. Recurrence was found outside the coagulation zone (extralesionary) and in high vascularized areas within the coagulation zone (intralesionary).
Isbert
C
C
Department of Visceral, Vascular and Thoracic Surgery, University Medical Center Benjamin Franklin, Freie Universität Berlin, Hindenburgdamm 30, D-12200 Berlin, Germany. isbert@ukbf.fu-berlin.de
Roggan
A
A
Ritz
J P
JP
Müller
G
G
Buhr
H J
HJ
Lehmann
K S
KS
Germer
C T
CT
D000818:Animals; D004867:Equipment Design; D005260:Female; D006498:Hepatectomy; D006358:Hot Temperature; D053685:Laser Therapy / Q000295:instrumentation / Q000379:methods*; D008114:Liver Neoplasms, Experimental / Q000473:pathology / Q000601:surgery*; D009364:Neoplasm Recurrence, Local / Q000517:prevention & control* / Q000601:surgery; D011817:Rabbits