Research progress on linear quadratic and biological equivalent dose models for high-dose-per-fraction radiotherapy

The linear quadratic (LQ) model and deduced biological equivalent dose (BED) model are widely applied in the radiobiological studies and the mathematic models of radiation oncology in clinical practice. However, the LQ model cannot accurately fit the experimental and clinical data in the high-dose region under the high-dose-per-fraction treatment mode. To resolve this issue, researchers have made modifications to the LQ models since 2008. In the paper, first, the theoretical basis and the application scope of LQ and BED models were introduced and the debate on whether LQ model is applicable to the high-dose-per-fraction radiotherapy was reviewed. Second, five modified models were introduced in two categories and their characteristics were summarized. Finally, current research situation and existing problems of radiotherapy using biological equivalent dose (BED) models were briefly summarized and the development trend of models was predicted. Key words: Neoplasm/stereotactic body radiotherapy; Linear quadratic model; Biological equivalent dose