Normal Tissue Tolerance to Reirradiation

As a result of longer survival times, even among patients with incurable malignancies, the prevalence of patients at risk of developing second primary tumours and/or locoregional recurrences in previously irradiated areas might increase. Consequently, the need for additional therapeutic measures providing local control and/or symptom palliation along different lines of treatment has emerged. This has resulted in increasing requests for delivering a second and sometimes even third course of radiation to target volumes within or close to previously irradiated anatomical areas. On the one hand, improved imaging and delivery techniques including image-guided and intensity-modulated radiotherapy might facilitate reirradiation of previously exposed regions of the body. On the other hand, late toxicity is of concern because it often causes serious impact on health-related quality of life. Therefore, knowledge about long-term recovery of occult radiation injury is of utmost importance. This chapter summarises available experimental and clinical data on the effects of reirradiation to various organs.