PARAMETERS OF LINEAR-QUADRATIC RADIATION DOSE-EFFECT RELATIONSHIPS - DEPENDENCE ON LET AND MECHANISMS OF REPRODUCTIVE CELL-DEATH

An analysis of mammalian cell radiation-dose survival curves, based on the linear-quadratic formalism, is shown to yield insights in the var ious components of damage that contribute to cell reproductive death. RBE-LET relationships of single-track lethal damage, sublethal damage, potentially lethal damage and DNA double-strand breaks are compared. Single-track lethal damage is derived to be composed of two components : (1) damage that remains unrepaired in an interval between irradiatio n and assay for proliferative capacity, with a very strong dependence on LET, and (2) potentially lethal damage that is only weakly dependen t on LET, similar to sublethal damage and DNA double-strand breaks. Th e results of this analysis lead to new interpretations of published ex perimental results and to suggestions for applications in radiotherapy .