Analysis of enhancement at small and large radiation doses for effectiveness of inactivation in cultured cells by combining two agents with radiation

Methods and materials: Data on clonogenic assays concerning the radio-enhancement effects of combined halogenated pyrimidines and hyperthermia or combined cisplatin and hyperthermia, as published in earlier reports, were analyzed according to the LQ-formula: S(D)/S(0) = exp−(αD + βD 2 ).

Effects of sensitizing agents on the linear parameter α and the quadratic parameter β are compared in order to evaluate differences depending on the applied dose, the possible relations to mechanisms of radiation sensitization and to derive suggestions for applications. Results: The values of the linear parameter α, which determines the effectiveness at low doses, are for all cell lines and all conditions more increased than the values of the parameter β which has a higher contribution at larger radiation doses.