Study on radiation effect to malignant tumors and its influence on metastasis

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1) From the results of study performed for evaluation of dose rate effect 7 Gy with low dose rate irradiation (LDR) corresponded nearly to LD_<100/30> for Jcl:ICR male mouse. Four Gy with high dose rate irradiation (HDR) was almost equivalent to 5.5 Gy with LDR on lethal effect, and 5.5 Gy with HDR nearly to LD_<50/30>. Six Gy with HDR was estimated at nearly 7 Gy with LDR. Further study on dose rate effect was made by evaluating the irradiation effects on DNA contents of cultured fibroblasts and chondrocytes. Five Gy with HDR was more inhibitive to DNA contents in cultured cells than with LDR. As the results it was confirmed that the radiation effects were influenced by dose rate even though the difference was only 1 to 20.2) An experimental study was performed on the effect of irradiation for primary lesion to the incidence of metastasis. The results of the study suggested that a single exposure of 3,5 and 10 Gy each to the transplanted VX2 carcinomas of rabbit femur increased the incidence of metastasis as compared with the non-irradiated control group.