Quantitative estimation of recovery parameters after combined action of ionizing radiation and chemical agents

Background: Treatment of ionizing radiation combined with chemical agents can enhance the inactivation of cells. The aim of this study was to determine the parameters involved in the inhibition of cell recovery. Materials and Methods: A mathematical model describing the process of recovery as a decrease in the effective radiation dose was used. The model includes two parameters, recovery constant and irreversible component. Both parameters were estimated quantitatively by using experimental survival and recovery data reported by others. Results: The inhibition of cell recovery might be done via either the damage of the mechanism of the recovery itself or via the formation of irreversible damage which could not be repaired at all. Both these processes could take place at the same time. Another mechanism was the higher probability to produce primary radiation damage without changing the recovery process. Conclusions: The results indicate the opportunity to search agents, selectively or simultaneously acting on the probability of recovery and the yield of irreversible radiation damage. The results obtained may have a practical use, rather than being concerned only with theoretical position.