ABSTRACT
It is becoming increasingly apparent that the linear quadratic model does not accurately predict the better-than-expected levels of tumor control that can be achieved with radiosurgery. Many radiobiologists agree that the assumptions upon which the standard linear quadratic model is based are not valid in doses of radiation that exceed 6 Gy/fraction. For example, brain metastases can be e‰ectively controlled at doses of 18-21 Gy in a single fraction, whereas doses in excess of 25 Gy would be predicted to be necessary for similar rates of tumor control. ese observations suggest that di‰erent mechanisms of response are at play in the setting of high-dose-per-fraction radiotherapy.
