<title>Diode laser thermotherapy in the treatment of hepatic tumors in rabbits</title>

Laser induced thermotherapy (LITT) has been recently developed for treating deep seated tumors. Diode laser (830 nm) is suitable for LITT, because of its high penetration in tissue. The present animal experiment was conducted to evaluate the performance of a diode laser for treating liver tumors in rabbits. Fifty-two New Zealand rabbits were grafted in liver with a Vx2 tumor model. They were treated at a tumor size of 8 mm diameter. A laser energy of 1 350 J (power: 1.5 W; irradiation time 900 s) was delivered through a 300 micrometer fiber implanted in the center of the tumor. Our experiment was divided in two parts: (1) A survival study: we compared the medians survival between untreated tumors (Group A, n equals 21) and irradiated tumors (Group B, n equals 21), (2) An evaluation of LITT efficiency on day 7 (Group C, n equals 5) and at day 14 (Group D, n equals 5). We compared at day 7 and day 14 the radiologic data (ultrasonography and MRI realized before and after irradiation) to the microscopic examinations (haematoxylin eosine stain and picrosirius red F3BA). The results were a median survival not significantly different in group B (laser) than in group A (control) and an efficiency only at short time (on day 7). There was a good correlation between radiologic data and microscopic examinations in groups C and D. The picrosirius red F3BA estimated the extent of thermal damage. In conclusion, these disappointing results are due to an insufficient irradiation of peritumoral tissue and to the Vx2 aggressivity (undifferentiated). Using multiple optical fiber could improve the LITT efficiency. The correlation between radiological and microscopic findings would allow us to quantify the results of LITT.