Is the linear-quadratic model appropriate for stereotactic irradiation of metastatic brain tumors?

Abstract

The biologically effective dose (BED) based on the linear-quadratic (LQ) model has been commonly used to evaluate the dose-effect relationships among the different fractionation schedules, but whether the LQ model is appropriate for hypofractionated (HF) high-dose stereotactic irradiation (STI) is uncertain. The validity of the model at high doses per fraction has been critically examined. In this study, STI of metastatic brain tumors was evaluated to suggest the applicability of the LQ model to HF high-dose radiotherapy. No significant difference was found between stereotactic radiosurgery (SRS) and HF stereotactic radiotherapy (SRT) in the analyses of 151 tumors. Furthermore, no significant differences were found among SRS, HF-SRT, and non-HF SRT in 117 metastatic lung adenocarcinomas. The results of this study suggest that BED calculation is a reasonable approach for careful dose-effect evaluation based on the LQ model for HF high-dose radiotherapy for metastatic brain tumors, especially lung adenocarcinomas.