Myelopathy following hyperfractionated accelerated radiotherapy for anaplastic thyroid carcinoma.

From 1975 to 1982, 32 patients with a diagnosis of anaplastic carcinoma of the thyroid were entered into a protocol of hyperfractionated accelerated radiotherapy. The tumor dose was 30-45 Gy at 1 Gy per fraction given 4 times a day at 3-h intervals. The results were disappointing with a median survival of less than 6 months. Two patients developed radiation myelopathy at 8 and 13 months, total spinal cord dose being 39.9 and 48.3 Gy, respectively. The risk of spinal cord damage was much higher than expected. The possible radiobiological causes and clinical implications are discussed.