Effects of modified fractionated irradiation on the growth of sarcoma 180 solid tumor in mouse

The present experimental study has been designed and carried out to investigate the effects of various doses and timings of fractionated irradiation of 6 MV X-rays obtained from a linear accelerator on sarcoma 180 solid tumors produced in DDO/Lee mouse. A total of 2700 to approx. 2800 cGy(or rad) was delivered with daily dose of 250/ cGy, 350cGy, and 450cGy every other day to the inoculated site starting on day 2,4,6, and 8 post-inoculation and the tumor size change was observed by measuring a maximum circumference of tumor bearing region. The dose experimentally established in the mouse for one half of animals to produce a solid tumor (TSD50) from ascitic mouse sarcoma 180 was 10/sup 3.87/ cells/ml. The effect of fractionated irradiation on days 2 and 4 post-inoculation was inhibitory to the growth of solid form tumor of experimentally produced sarcoma 180 (p<0.001). The growth of tumor was also inhibited when irradiated on days 6 and 8 post-inoculation but the grade was less. Histologically tumor cells of mouse sarcoma 180 produced in the experimental animal were shown to be destroyed and eradicated by radiation once they were responsive to X-irradiation. The present study suggests that a small or early tumor is benefitted by a small daily dose(e.g. 250 cGy) irradiation whereas a moderately advanced tumor is beneficially treated with a relatively high dose (e.g. 450 cGy) irradiation. A large tumor responded very poorly to irradiation