title: Quantitation of the response of human tumor spheroids to daily radiation exposures.
abstract: Two human tumor lines, NB-100 neuroblastoma and C-32 melanoma, were grown as multicellular tumor spheroids (MTS) and exposed to daily doses of gamma rays, 5 days per week. It required daily doses of 200 rad to arrest the growth of the NB-100 MTS, while 350 rad per day was required to arrest the growth of the C-32 MTS. Calculation of the delay in time to grow 200 um beyond the original size yielded similar differences in radiation resistance. When the volume of the treated MTS was expressed as a fraction of their potential volume and plotted as a function of cumulative dose, there appeared to be little fraction size dependence over the range studied. This prediction was tested experimentally and confirmed: daily administration of two 100 rad doses separated by 4 hours to NB-100 MTS was only marginally less effective than a daily single dose of 200 rad. These data suggest that MTS may prove to be valuable tools in studying the response of human tumors to clinical exposure protocols, including hyperfractionation.
mesh_terms: D002460:Cell Line; D002588:Cesium Radioisotopes; D004307:Dose-Response Relationship, Radiation; D005720:Gamma Rays; D006801:Humans; D008954:Models, Biological; D009369:Neoplasms / Q000473:pathology / Q000532:radiotherapy*
chemical_list: D002588:Cesium Radioisotopes