Tumour growth delay and normal tissue reations induced by fractionated, low-dose-rate irradiation
bookPart
Experiments have been carried out to investigate the effectiveness of X-rays applied at dose rates of 390 and 20400rad/h (1.08 and 56.7mGy/s) for induction of tumour responses and normal tissue damage. This work is an extension of earlier studies performed at dose rates of about 100rad/h (0.28mGy/s). The dose rates of 100 and 20400rad/h correspond to values presently employed for low-dose-rate and high-dose-rate external beam irradiations. The aim was to determine whether the therapeutic ratio for doses applied at an intermediate dose rate, 390rad/h, is the same as that obtained at 100rad/h. A rat rhabdomyosarcoma was used to evaluate the effectiveness of four daily doses of 300kV X-rays applied at a dose rate of 390rad/h as compared with four daily doses at a dose rate of 20400rad/h. Skin of the foot was used as a normal tissue. Four daily doses at dose rates of 390 or 20400rad/h were administered, followed 3 days later with an acute dose of 1500rad (15Gy). Tumour growth delay and severety of skin injury were the end points to be examined. Treatments of four daily doses administered at high dose rate (20400rad/h) are more effective in inducing tumour growth delay as compared with treatments of four daily doses administered at low dose rate (390rad/h). Significant differences in skin reactions were observed when doses were applied at a dose rate of 390rad/h as compared with acute irradiation (20400rad/h) implying that doses applied at 390rad/h were more efficient.
TNO Identifier
355670
Publisher
International Atomic Energy Agency (IAEA)
Source title
Radiobiologisch research and radiotherapy, Report on the International Symposium, 22 to 26 November 1976, Vienna
Editor(s)
Singh, B.B.
Pages
11-20
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