Transplant immunity in hamsters treated with ultrasound

Hamsters with subcutaneous fibrosarcomas were treated by excision and by exposure to 5-MHz ultrasound for six minutes at an intensity of 3 W/sq cm. Rates for successful elimination of the tumors were between 80% and 90% and were not significantly different for the two methods of treatment. After 30 days, the animals were challenged with the same tumor cells. Animals successfully treated with ultrasound or excision required at least 10 times as many cells to produce a tumor as controls, indicating that eradication of the tumor by ultrasound induced a level of transplant immunity at least as good as that resulting from surgical excision.