Using cell cycle kinetics to determine tumor control probability of standard radiotherapy dose fractionation schedule for breast adenocarcinoma

Abstract

Dose fractionation is utilized in clinical radiotherapy to allow normal tissue repair and increase tumor radiosensitivity through reoxygenation and redistribution to a relatively radiosensitive phase of the cell cycle. In this study, the cell cycle kinetics of a breast adenocarcinoma tumor and linear-quadratic dose-response were used to determine the TCP (tumor control probability) of different dose fractionation schedules employed in radiotherapy treatment of breast tumors. Results show that the simulated growth behavior of the tumor population exhibited similarities with the in vitro growth curve. Dose fractionation schedules of 45 Gy total dose, delivered over 3 weeks; and 30 Gy total dose, delivered over a week, show considerable fraction of tumor cell death that lead to a high TCP. In the case of 50 Gy total dose delivered over 5 weeks, net growth in relative tumor population was obtained, resulting in a small TCP. Based on the calculated TCPs, the dose per fraction and total treatment period are essential factors that determine the effectiveness of a dose fractionation regimen.