Effects of Roentgen Irradiation on the Tumor Bed: II. The Inhibiting Action of Different Dose Levels of Local Pretransplantation Roentgen Irradiation on the Growth of Mouse Mammary Carcinoma

Abstract

In a previous report (1) we confirmed that local roentgen irradiation of the tumor bed inhibits the growth of transplanted mouse mammary carcinoma. These experiments illustrate the significance of the irradiated normal tissues of the host in suppressing the growth of the tumor, because the tumor cells inoculated into the irradiated bed had received no irradiation. In the previous experiments emphasis was placed on the comparison between the growth of the tumor transplants in irradiated and shielded sites within the same animals. A single dose of 1500 r/air was given to one leg of young ZBC mice, and 48 hours later both the irradiated and the opposite shielded leg were inoculated with a tissue suspension of spontaneous mammary carcinoma developed in Z female mice and maintained by serial transplantation in ZBC male mice. The inhibition of the growth of several different tumors inoculated into the irradiated leg was striking when compared with the tumor in the shielded leg. The tumor in the shielded leg grew at the same rate as tumors in nonirradiated control animals of the same age and strain. The present report deals with a study of the effect of different dose levels of pretransplantation irradiation (PTI). In this series of experiments the inoculation of tumor cells was limited to the irradiated site, thus allowing determination of the effect of PTI on the survival of the animals. A detailed study of the growth rate of tumors developing in both irradiated and nonirradiated tissues was carried out.