Evidence for radiation-induced Bystander effects and relevance to radiotherapy and to radiation protection

Full text: There are two major arms of radiation science in which Bystander effects (ByEff) could be of practical importance: radiotherapy and risk assessment. Basic biological principles, including dose-response relationships that have become dogma in the context of targeted effects of IR must now be reconsidered. The direct effects of radiation and the bystander components had to be reinvestigated to show the difference between them. It may be necessary to introduce a factor for ByEff's when calculating dose to both normal tissues and tumor. Presumably the relative effects on normal or tumor tissues could be different and that difference may not be always predictable. In relation to radiation protection, the existence of RIByEff's raises important questions for the way radiation dose is measured and modeled. The biological effect of exposure to low-doses radiation is likely to vary between individuals and between organs in one the same individual. Further studies on non-targeted effects should contribute to the establishment of adequate environmental and occupational radiation protection standards. This lecture looks at the history, the current data and controversies that are now beginning to resolve the questions concerning the mechanisms underlying the induction and transmission of ByEff. Especially, effects on radiotherapy and radiation protection are discussed