The risk of chronic progressive radiation myelopathy.

Five cases of chronic radiation myelopathy (four of the thoracic and one of the cervical cord) are presented together with a short summary of cases already published. The important influence of the fractionation scheme is stressed. A dose not exceeding 4400 rd in the thoracic myelon (20 X 2000 rd, 5 times per week, plus 10 X 40 rd - or 15 X 200 rd plus 15 X 90 rd, 5 times per week, - or 8 X 330 rd, three times per week, plus 15 X 80 rd 5 times per week) is considered to be a safe limit. In view of the scarcity of adequately documented cases of cervical myelopathy, it is recommended to keep dose limits about 10% lower than in the thoracic region and to avoid high single doses in curative treatments. Hypertension may increase the risk of radiation myelopathy (case nr. 5).