Postoperative radiotherapy of primary spinal cord tumors

During the 30 year period from 1957 to 1986, 42 patients with primary tumors arising from the spinal cord or cauda equina received postoperative irradiation at the University of California, San Francisco. Twenty-one patients had ependymomas: 18 were localized to one site, and 3 diffusely involved the cord. There were 12 patients with low grade astrocytomas and 3 with highly anaplastic astrocytoma or glioblastoma multiforme. All astrocytomas were localized at presentation. In 6 cases tissue was insufficient to permit a histologic diagnosis. Thirty-nine patients (93%) received total radiation doses ranging between 45.0-54.7 Gy using standard fractionation. The 10-year actuarial disease-specific survival rate for patients with localized ependymoma was 93%; 33% of these tumors recurred locally. The corresponding rate for diffuse ependymomas was 50%; the spinal disease was controlled in all 3 patients, but one developed a cerebral metastasis despite prophylactic cranial irradiation. Low-grade astrocytoma patients had a 10-year actuarial disease-specific survival rate of 91%, with 33% of these tumors recurring locally. No patient with highly anaplastic astrocytoma or glioblastoma multiforme survived longer than 8 months; all of these tumors recurred locally, and two of the three also developed diffuse craniospinal axis metastases. Local recurrence for ependymoma was delayed as long as 12 years following treatment, while all but one astrocytoma failure occurred within 3 years of treatment. No significant dose-response relationship with respect to local control was noted for either localized ependymomas or low grade astrocytomas. One patient developed radiation myelitis after receiving 50.4 Gy with standard fractionation. These results indicate that patients who undergo postoperative irradiation for low grade spinal astrocytomas and localized spinal ependymomas achieve excellent survival. However, despite treatment with total radiation doses taken to the practical limit of spinal cord tolerance, local failure remains common.