Biologically Effective Dose (BED) or Radiation Biological Effect (RBEf)?

Abstract

The current radiosensitive studies are described with linear-quadratic (LQ) cell survival (S) model for one fraction with a dose d. As result of assuming all sublethally damaged cells (SLDCs) are completely repaired during the interfractions, that is, no presence of SLDCs, the survived cells are calculated for a n-fractionated regimen with the LQ S(n,D) model. A mathematically processed subpart of LQS(n,D) is the biologically effective dose (BED) that is used for evaluating a so-called "biological dose." The interactions of ionizing radiation with a living tissue can produce partial death or sublethal damage from healthy or sublethally damaged cells. The proportions of the killed and sub-lethally damaged cells define the radiation biological effects (RBEfs). Computational simulations using RBEFs for fractionated regimens let calculating tumor control probability. While the derivation of the LQ S(n,D) considers a 100% cell repair, that is, 0% of sublethally damaged cells (SLDCs), the radiobiological simulators take into account the presence of SLDCs, as well as a cell repair <100% during the interfractions and interruption. Given "biological dose" does not exist, but RBEf, there was need for creating the BED. It is shown how some uses of BED, like the derivation of EQ2D expression, can be done directly with the LQ S(n,D).

Differential effects of radiation fractionation regimens on glioblastoma

“…After 10 days colonies were stained with crystal violet (0.5% w/v, 1:1 methanol: distilled water) and then imaged and quantitated using a vSpot ® Spectrum ELISpot/FluoroSpot Reader System and software (Autoimmun Diagnostika Gmbh, Straßberg, Germany). From the clonogenic cell survival fractions the linear quadratic (LQ) equation using Prism version 8.4.0 for Windows (GraphPad, San Diego, California, United States) was applied to calculate the cell survival (S) α/β ratio and biologically effective dose as outlined below [15] and BED values summarised in Additional file 1: Table S1:…”

“…While 10 and 20 Gy are biologically effective in vitro they are unlikely to be suitable in fractionated regimens for brain cancer patients, due to radiation-induced cell injury to adjacent healthy brain parenchyma. Therein, we assessed a one-week fractionated regimen to compare the relative efficacy of 10 Gy/5 f vs 10 Gy/2 f. We first assessed the theoretical cell survival fractions and BED of the RT regimens (Additional file 1: Table S1) [15]. Not surprisingly, multi-fraction RT regimens reduced the cell survival fraction and increased the biologically effective doses compared to single-fraction doses (Additional file 1: Table S1).…”