Interaction of ultrasound with neoplastic tissue. II. Systemic effects after local sonic irradiation.

Local sonic irradiation was applied to subcutaneously implanted Furth-Columbia rat Wilms' tumor. The weight and the rate of tritiated thymidine uptake were measured in host organs distal to the application field. Kidney and spleen weights were inhibited by the Wilms' tumor, and sonication of the tumor removed all or part of this inhibition. Liver weight was increased after sonication of tumor-bearing rats but not in nontumor-bearing rats. This may have been a response to tumor-specific substances released into the circulation by sonic destruction of tumor tissue. The adrenals enlarged as a response to the stresses of both tumor-bearing and of sonication. Animals were implanted on both sides with the Wilms' tumor and on without any break in the growth curve while the sonicated right tumor was inhibited. These data suggest that the therapeutic effect of ultrasound is due solely to local factors and that systemic sequelae of some irradiation are unrelated to tumor inhibition.