title: DEGRO practical guidelines for radiotherapy of non-malignant disorders: Part I: physical principles, radiobiological mechanisms, and radiogenic risk.
abstract: OBJECTIVE
  Synopsis of the introductory paragraph of the DEGRO consensus S2e-guideline recommendations for the radiotherapy of benign disorders, including physical principles, radiobiological mechanisms, and radiogenic risk.
  
  
  METHODS
  This work is based on the S2e-guideline recommendations published November 14, 2013. The basic principles of radiation physics and treatment delivery, evaluation of putative underlying radiobiological mechanisms, and the assessment of genetic and cancer risk following low-dose irradiation will be presented.
  
  
  RESULTS
  Radiation therapy of benign diseases is performed according to similar physical principles as those governing treatment of malignant diseases in radiation oncology, using the same techniques and workflows. These methods comprise usage of orthovoltage X-ray units, gamma irradiation facilities, linear accelerators (LINACs), and brachytherapy. Experimental in vitro and in vivo models recently confirmed the clinically observed anti-inflammatory effect of low-dose X-irradiation, and implicated a multitude of radiobiological mechanisms. These include modulation of different immunological pathways, as well as the activities of endothelial cells, mono- and polymorphonuclear leukocytes, and macrophages. The use of effective dose for radiogenic risk assessment and the corresponding tumor incidence rate of 5.5%/Sv are currently controversially discussed. Some authors argue that the risk of radiation-induced cancers should be estimated on the basis of epidemiological data. However, such data are rarely available at present and associated with high variability.
  
  
  CONCLUSIONS
  Current radiobiological studies clearly demonstrate a therapeutic effectiveness of radiation therapy used to treat benign diseases and implicate various molecular mechanisms. Radiogenic risks should be taken into account when applying radiation treatment for benign diseases.
authors.affiliation: Department of Radiotherapy and Radiation Oncology, Hospital Weiden, Söllnerstrasse 16, 92637, Weiden, Germany, berthold.reichl@kliniken-nordoberpfalz.ag.
authors.forename: Berthold
authors.initials: B
authors.lastname: Reichl
authors.forename: Andreas
authors.initials: A
authors.lastname: Block
authors.forename: Ulrich
authors.initials: U
authors.lastname: Schäfer
authors.forename: Christoph
authors.initials: C
authors.lastname: Bert
authors.forename: Reinhold
authors.initials: R
authors.lastname: Müller
authors.forename: Horst
authors.initials: H
authors.lastname: Jung
authors.forename: Franz
authors.initials: F
authors.lastname: Rödel
mesh_terms: D005858:Germany; D006801:Humans; D009683:Nuclear Medicine / Q000592:standards*; D018787:Radiation Oncology / Q000592:standards*; D011835:Radiation Protection / Q000592:standards*; D011878:Radiotherapy / Q000592:standards*; D011880:Radiotherapy Planning, Computer-Assisted / Q000592:standards*; D012955:Societies, Medical