title: Dose-rate effects in the radiation response of four human tumour xenografts.
abstract: The radiation repair capability of four human tumour xenograft lines, two adenocarcinomas of the pancreas, an adenocarcinoma of the breast and a melanoma, has been investigated by means of a soft agar clonogenic assay. Dose-rate dependence studies at 150, 7.6 and 1.6 cGy/min and split-dose experiments, have been performed. Results indicate a good correlation between split-dose recovery and the dose-sparing achieved by irradiation at 1.6 cGy/min when compared to acute irradiation in 3 of the 4 tumour lines. The HX118 melanoma showed dose-sparing at dose-rates of 7.6 and 1.6 cGy/min and a substantial ability to perform recovery between split doses of radiation, whereas HX32, a pancreatic carcinoma, showed little dose-sparing and a correspondingly small degree of split-dose recovery. The HX99 breast carcinoma, was aberrant in showing the greatest split-dose recovery of the four lines but only a moderate extent of low dose-rate sparing. Data have been fitted by two recently described models for radiation dose-rate dependence; the incomplete repair model of Thames and the Lethal Potentially-Lethal (LPL) model of Curtis. Curves were fitted better by the Thames model which provided a good fit for data from 3 of the 4 xenografted human tumour lines. HX99 produced dose-rate dependence survival curves that were not well fitted by either model.
mesh_terms: D000230:Adenocarcinoma / Q000532:radiotherapy*; D000818:Animals; D001943:Breast Neoplasms / Q000532:radiotherapy*; D002460:Cell Line; D002470:Cell Survival / Q000528:radiation effects*; D003037:Cobalt Radioisotopes / Q000627:therapeutic use; D003114:Colony-Forming Units Assay; D005260:Female; D006801:Humans; D008297:Male; D008545:Melanoma / Q000532:radiotherapy*; D051379:Mice; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D010190:Pancreatic Neoplasms / Q000532:radiotherapy*; D011867:Radioisotope Teletherapy; D011879:Radiotherapy Dosage; D012878:Skin Neoplasms / Q000532:radiotherapy*; D014410:Tumor Stem Cell Assay
chemical_list: D003037:Cobalt Radioisotopes