Current and future strategies in radiotherapy of childhood low-grade glioma of the brain. Part I. Treatment modalities of radiation therapy

Background: Treatment of childhood low-grade gliomas is a challenging issue owing to their low incidence and the lack of consensus about ''optimal'' treatment approach. Material and Methods: Reports in the literature spanning 60 years of radiation therapy, including orthovoltage, megavoltage and recently modern high-precision treatments, were reviewed with respect to visual function, survival, prognostic factors, dose prescriptions, target volumes, and treatment techniques. Based on these experiences, future strategies in the management of childhood low-grade glioma are presented. Results: Evaluation of published reports is difficult because of inconsistencies in data presentation, relatively short follow-up in some series and failure to present findings and results in a comparable way. Even with the shortcomings of the reports available in the literature, primarily concerning indications, age at treatment, dose response, timing and use of ''optimal'' treatment fields, radiation therapy continues to play an important role in the management of these tumors achieving long-term survival rates up to 80% or more. Particularly in gliomas of the visual pathway, high local tumor control and improved or stable function is achieved in approximately 90% of cases. Data on dose-response relationships recommend dose prescriptions between 45 and 54 Gy with standard fractionation. There is consensus now to employ radiation therapy in older children in case of progressive disease only, regardless of tumor location and histologic subtype. In younger children, the role of radiotherapy is unclear. Recent advances in treatment techniques, such as 3-D treatment planning and various ''high-precision'' treatments achieved promising initial outcome, however with limited patient numbers and short follow-ups. Conclusions: Radiation therapy is an effective treatment modality in children with low-grade glioma regarding tumor control and improvement and/or preservation of neurologic function or vision, respectively. More prospective studies are needed to address the impact of modern radiation therapy technologies (including intensity-modulated radiotherapy) on outcome especially in the very young and to define the role of radiation therapy as a part of a comprehensive treatment approach. The forthcoming prospective trial SIOP/GPOH LGG RT 2003 is addressing this issue. (orig.)