Influence of high-intensity focused ultrasound on the development of metastases

Objective: The hypothesis that exposure of a solid tumor to high-intensity focused ultrasound (HIFU) could lead to an increase of metastases was investigated in an animal model. Methods: The highly metastatic AT-6 Dunning R3327 rat prostate cancer subline was implanted into the hind limb of Fisher-Copenhagen rats and was exposed to 1 pulse/mm(2) tumor (acoustical power 1,000 W/cm(2)) delivered by an experimental machine (Ablatherm, Technomed, France), or the animals were sham treated, as soon as the tumor had reached a volume of 175-225 mm(3), The tumor-bearing leg was amputated 24 h later and the number of metastases examined 12 weeks thereafter at autopsy. Results: Metastases were seen in 3 (23%) of the 13 animals exposed to HIFU and in 4 (25%) of the 16 sham-treated animals; this is not significantly different. There was also no significant difference in weight of the lungs that contained metastases between sham-treated and HIFU-treated animals, Conclusion: Metastatic spread of animal tumors with a high metastatic potential is not enhanced by HIFU exposure.