THE ROLE OF PROPHYLACTIC SPINAL IRRADIATION IN LOCALIZED INTRACRANIAL EPENDYMOMA

A review of the clinical literature on ependymoma, published between 1969 and 1989, was carried out to assess the influence of tumor grade and site, tumor control at the primary site, and extent of irradiation on the incidence of spinal seeding after initial treatment. The pooled data show that the incidence of seeding was 8.4% (7/83) for high grade tumors and 4.5% (6/132) for low grade tumors. Seeding occurred more frequently in infratentorial tumors than in supratentorial tumors. For high grade tumors the incidence was 0% (0/26) for supratentorial and 15.7% (6/38) for infratentorial lesions; for low grade tumors the respective incidence was 2.7% (1/37) and 5.5% (4/73). Spinal seeding was 9.5% (15/157) in the event of failure at the primary site compared to 3.3% (4/122) when local control was achieved. The development of spinal metastases was not influenced by the extent of irradiation. For high grade tumors the incidence was 9.4% (5/53) with spinal irradiation and 6.7% (2/30) without prophylactic treatment; for low grade tumors the respective values were 9.3% (4/43) and 2.2% (2/89). These results indicate that tumor grade, tumor localization, and control of the tumor at the primary site are all factors which may influence the risk of spinal seeding. On the present evidence spinal metastases are not prevented by prophylactic spinal irradiation, regardless of tumor grade and site.