Understanding the Radiation Adaptive Response: General Methodology and Theoretical Approaches to the Study of the Radioadaptation Phenomenon.

Objectives: The radiation-induced adaptive response (RAR), also referred to as radioadaptation, describes modifications of biological radiation sensitivity following prior exposure to low doses or low dose-rates of ionizing radiation. Despite extensive experimental evidence, RAR remains difficult to reproduce consistently and lacks a unified quantitative and methodological framework. The objective of this study was to develop a systematic biophysical approach enabling coherent analysis and comparison of RAR experiments performed under different irradiation protocols. Methods: We formulated a dose- and time-dependent adaptive response function characterized by transient, memory-like dynamics. On this basis, we derived analytical expressions describing RAR under multiple irradiation schemes, including priming-challenge protocols, radiation training, constant low dose-rate exposure, and variable dose-rate scenarios. A unified relative endpoint parameter was introduced to quantify the magnitude of the adaptive response across experimental designs. Results: The proposed framework yields explicit expressions for the adaptive response parameter under diverse exposure conditions and demonstrates how RAR magnitude depends on dose, dose-rate, and time interval between exposures. The methodology enables consistent normalization of experimental endpoints, facilitates parameter estimation from empirical data, and clarifies conditions under which adaptive effects are expected to emerge or vanish. Conclusion: This work provides a coherent and transferable methodological foundation for quantitative RAR research. The framework improves comparability between experimental studies and supports mechanistic interpretation of low dose adaptive effects, while remaining primarily applicable to controlled experimental systems rather than population-level radiation risk assessment.