paediatrics Brussels 17

Childs Nerv Syst DOI 10.1007/s00381-009-0892-9

INVITED PAPER

Three-dimensional conformal radiation therapy for ependymoma

Thomas E. Merchant

Received: 26 March 2009 # Springer-Verlag 2009

Purpose

Abstract Introduction The application of conformal radiation thera- py in the treatment of pediatric ependymoma is a success story resulting from advances in radiation therapy planning and delivery. These advances occurred at a time when clinical trial results confirmed that radiotherapy avoidance strategies were unsuccessful. Discussion Investigators have been keen to confirm the promise of newer radiation therapy methods even for the youngest children. When preliminary results suggested that high-dose focal irradiation could be safely administered through systematic targeting and that cognitive function could be preserved, investigators moved to include confor- mal therapy in the frontline management of children regardless of age. The results with postoperative conformal radiation therapy were further enhanced when neurosur- geons increased the rate of gross-total resection and recognized that second surgery could be safely accomplished after incomplete initial resection. With more than a decade of experience, the role of conformal radiation therapy in the treatment of childhood ependymoma has been firmly established as investigators consider new trials to increase disease control and improve functional outcomes.

Ependymoma describes a diverse group of central nervous system (CNS) tumors for which the very young are disproportionably represented; nearly half of pediatric cases occur in children under the age of 4 years [ 1 ]. The factor of age is a critical point for successful treatment of ependy- moma that requires aggressive surgery and high-dose postoperative radiation therapy. Incomplete resection and high rates of local failure characterize past institutional and cooperative group series for older children [ 2 – 10 ]. When radiation therapy avoidance was the hallmark of clinical trials for younger children, results were inferior to those achieved when radiation therapy was administered as a part of frontline management [ 11 – 14 ]. Two decades ago, radiation therapy for ependymoma consisted of craniospinal irradiation with or without chemotherapy. Long-term event-free survival was less than 40% [ 15 ]. Patients experienced tumor progression at the primary site because most had measurable residual tumor at the time of irradiation. Because of concern about neuraxis dissemination, especially in patients with high-grade tumors, craniospinal and boost irradiation of the primary site was administered postoperatively. Those who survived suffered debilitating side effects. Recognition that primary site irradiation was equivalent to craniospinal irradiation occurred at a time when radiotherapy avoidance was becoming the regimen of choice for younger patients and the advantage of focal treatment, even using conventional techniques, could not be realized because of the persistently high rates of local failure [ 16 ]. Three-dimensional conformal radiation therapy trials were developed in the early 1990s at major medical centers in the USA. Supported by government contracts, these trials showed that radiation dose to prostate, head and neck, and

Keywords Radiation therapy . Pediatrics . Ependymoma . Brain tumor

T. E. Merchant ( * ) Department of Radiological Sciences, Mail Stop 220, St. Jude Children ’ s Research Hospital, 262 Danny Thomas Place, Memphis, TN 38105-3678, USA e-mail: thomas.merchant@stjude.org