The role of the Biological Effective Dose (BED) was developed to account for sub-lethal DNA repair effects during exposure and the resulting decrease in the clinical effect of the radiation. In conventional radiotherapy, where treatment times are short (≤10 minutes), sub-lethal repair is minimal. However, in radiosurgery, where treatments can take tens of minutes to deliver, the overall treatment time can reduce the BED of a treatment by a significant amount. This effect, evidenced originally in clonogenic cell survival studies, then animal models, has now been shown to have an important influence in clinical outcomes of SRS. The rationale for prescribing according to the Biological Effective Dose will be explored.
