Responses of rat rhabdomyosarcoma cells to multiple daily dose fractions and low dose rate gamma radiation

A comparison of the efficacy of two regimens, low dose rate irradiation and multiple daily dose fraction irradiation, was the main objective of the experiments described. Rat rhabdomyosarcoma (R-1) cells, which can be cultured in vivo and in vitro were used. Dose-survival curves were derived for cells treated in vitro and in vivo and assayed in vitro with the colony forming assay. DNA profiles of treated R-1 cells were obtained with a flow cytofluorometer. Repair of sublethal damage and redistribution of cells over the cell cycle phases during treatment was observed. Treatments with dose fractions of 2 or 4 Gy every 2 or 4 hours, respectively, were more effective than the treatment with doses of 1 Gy every hour and were less effective than treatments with acute single doses