[Normal tissue tolerance to external beam radiation therapy: peripheral nerves]. / Dose de tolérance à l'irradiation des tissus sains: les nerfs périphériques.

Plexopathies and peripheral neuropathies appear progressively and with several years delay after radiotherapy. These lesions are observed principally after three clinical situations: supraclavicular and axillar irradiations for breast cancer, pelvic irradiations for various pathologies and limb irradiations for soft tissue sarcomas. Peripheral nerves and plexus (brachial and lumbosacral) are described as serial structures and are supposed to receive less than a given maximum dose linked to the occurrence of late injury. Literature data, mostly ancient, define the maximum tolerable dose to a threshold of 60 Gy and highlight also a great influence of fractionation and high fraction doses. For peripheral nerves, most frequent late effects are pain with significant differences of occurrence between 50 and 60 Gy. At last, associated pathologies (diabetes, vascular pathology, neuropathy...) and associated treatments have probably to be taken into account as additional factors, which may increase the risk of these late radiation complications.

[Normal tissue tolerance to external beam radiation therapy: adult bone]. / Dose de tolérance à l'irradiation des tissus sains: l'os chez l'adulte.

Radiation tolerance for bone tissue has been mostly evaluated with regard to bone fracture. Main circumstances are mandibula osteoradionecrosis, hip and costal fracture, and patent or radiologic fractures in the treated volume. After radiation therapy of bone metastasis, the analysis of related radiation fracture is difficult to individualize from a pathologic fracture. Frequency of clinical fracture is less than 5% in the large series or cohorts and is probably underevaluated for the asymptomatic lesions. Women older than 50 years and with osteoporosis are probably the main population at risk. Dose-effect relations are difficult to qualify in older series. Recent models evaluating radiations toxicity on diaphysa suggest an important risk after 60 Gy, for high dose-fraction and for a large volume.