Modelling variable proton relative biological effectiveness for treatment planning

Br J Radiol. 2020 Mar;93(1107):20190334. doi: 10.1259/bjr.20190334. Epub 2019 Nov 18.


Dose in proton radiotherapy is generally prescribed by scaling the physical proton dose by a constant value of 1.1. Relative biological effectiveness (RBE) is defined as the ratio of doses required by two radiation modalities to cause the same level of biological effect. The adoption of an RBE of 1.1. assumes that the biological efficacy of protons is similar to photons, allowing decades of clinical dose prescriptions from photon treatments and protocols to be utilized in proton therapy. There is, however, emerging experimental evidence that indicates that proton RBE varies based on technical, tissue and patient factors. The notion that a single scaling factor may be used to equate the effects of photons and protons across all biological endpoints and doses is too simplistic and raises concern for treatment planning decisions. Here, we review the models that have been developed to better predict RBE variations in tissue based on experimental data as well as using a mechanistic approach.

Publication types

  • Review

MeSH terms

  • Algorithms
  • Animals
  • Cell Line, Tumor
  • DNA / radiation effects
  • DNA Repair
  • Humans
  • Models, Biological
  • Models, Theoretical*
  • Monte Carlo Method
  • Neoplasms / radiotherapy*
  • Organs at Risk / radiation effects
  • Photons / therapeutic use
  • Proton Therapy / methods*
  • Radiation Injuries*
  • Radiotherapy Planning, Computer-Assisted
  • Relative Biological Effectiveness*


  • DNA