ABSTRACT
Up to this point, the killing of tumor cells by the α-and βo-inactivation mechanisms of the linear-quadratic (LQ) model has been described and justified with experimental data for single cells irradiated in vitro, where biological, chemical and physical factors that impact outcome can be rigorously controlled. The question now arises as to whether we can be sure that these parameters for cell inactivation describe reliably the intrinsic radiosensitivity of tumor clonogens in vivo. Three different sets of experimental data that speak to this point are described
in the following sequence: the irradiation of cells in multicellular spheroids, the irradiation of cells in solid rodent tumors and the in vitro assays of intrinsic radiosensitivity (SF2Gy) of human cancer cells released from biopsy specimens.
