Normal tissue tolerance to external beam radiation therapy: The mandible

Describing dose constraints for organs at risk in external beam radiotherapy is a key-point in order to maximise the therapeutic ratio. In head and neck irradiation, mandible is frequently exposed to ionising radiation-related complications. Those complications will be exposed after a short description of anatomical and physiopathological aspects. A literature search was performed using the Pubmed-Medline database, with following keywords "Osteoradionecrosis, Radiotherapy, Mandible, Toxicity, Organ at risk, Trismus". Incidence and dose constraints will be reported. The incidence of osteoradionecrosis decreased since the 1990s, but it remains a dreaded late complication of head and neck cancer radiotherapy. It essentially occurs with cumulative doses of 66 Gy on the mandible (standard fractionation) applied to a significant volume. Respecting oral care is crucial to avoid this kind of complication. The respect of the dose-constraint described should not lead to undertreat tumor bed in a curative intent. Trismus related to ionising radiation is poorly described. Literature data cannot lead to describe precise dose constraints. (C) 2010 Societe francaise de radiotherapie oncologique (SFRO). Published by Elsevier Masson SAS. All rights reserved.