Tolerance dose of the spinal cord on radiation myelopathy.

Abstract

Radiation myelopathy has developed in 9 cases among irradiated patients as a side effect following radiotherapy for malignant tumors. The dose to the spinal cord was 5, 000-10, 000 rads, the over all treatment time 42-71 days. Several causative factors of the radiation myelopathy were picked up.The degree of radiation influences in the spinal cord seem to be time-dose dependent, as reported by Boden and Pallis. A recommended tolerance dose to spinal cord was over 4, 000 rads and over 5, 000 rads according to Tsuya's and Friedman's reports respectively and an NSD* of 1, 300 rets and 1, 500 rets was recommended by Maier and Phillips respectively. From the data presented it is apparent that degree of occurrence of radiation myelopathy depends greatly on fractionation and irradiation dose. When the patients are treated in more than 21 fractions at a daily dose of 200 rads and the dose to the spinal cord irradiated is more than 5, 000 rads, it can be considered to be the critial level for radiation myelopathy.