A Logarithmic Formula to Describe the Relationship between the Increased Radiosensitivity at Low Doses and the Survival at 2 Gray

Objectives: Intrinsic radiosensitivity at doses used in radiotherapy is linked to hypersensitivity (HRS)and increased radio resistance (IRR) at low doses. The aim of this study was to explore this relationship. Methods: Survival curves for 18 human tumour cell lines were analysed, using two models to fit the data points in order to extract the necessary parameters relevant for this study. Results: The IRR ratio αs/αr versus the survival at 2 gray (Gy) can be described by a logarithmic relation which leads to a series of straight lines. Conclusion: The relationship obtained implies that there is a direct link between HRS/IRR and survival at clinically relevant doses of 2 Gy.