Theoretical Exploration on Ultra-fractionated Radiotherapy

Key words: 
• hyper-radiosensitivity /
• ultra-fractionation /
• 50% tumor control rate

Abstract: Based on the survival data of human hepatoma SMMC-7721 and normal liver L02 cells irradiated with γ-rays at 0.3 Gy and 2 Gy, the possibility of uhra-fractionated radiotherapy is discussed in this paper. According to calculations, it is found that if the difference in cell survival between target tumor and adjacent normal tissue is up to 3%, radiotherapy using HRS would be realized through uhra-fractionation. Furthermore, the low-dose response is time-dependent. After analyzing this phenomenon, it was pointed that there would be a correlation between fractionation interval and the duration of cell G2 phase.