A multimode radiobiological model for advanced radiation therapy

Reliable radiobiological modeling is essential to the consistent dosimetric analysis and outcome comparison between conventionally fractionated radiation therapy (CFRT) that employs small daily doses (1.8-4Gy) and stereotactic body radiotherapy (SBRT) that employs large daily doses (> 5Gy). This work investigates a new radiobiological model, the multimode (MM) model, for both CFRT and SBRT.The MM model assumes the existence of different modes of cell killing because of unsuccessfully repaired radiation damage to the cell DNA by any number of ionization events (or radiation tracks). The validity of the multimode model was tested using previously published survival fractions of various cell lines. A comparison of the goodness-of-fit of the linear quadratic (LQ), multitarget (MT), universal survival curve (USC) and MM models was made to the survival curve of 12 non-small-cell lung cancer cell line. The same agreement was obtained between the USC and MM models with the survival data, which was significantly better than that with the LQ and MT models. The multimode model is a comprehensive model that may offer a superior description of the mammalian cell survival curve in both conventional and ablative dose ranges, which can be used for designing new fractionation schemes and predicting and understanding treatment outcomes for both CFRT and SBRT.