Radiotherapy

Radiation therapy is an essential component of treatment for many children and adolescents with CNS malignancies. This chapter provides an overview of radiation oncology, from basic concepts of physics (photon, proton, and electron therapy) and radiobiology (DNA damage and dose fractionation) to details about the planning process (immobilization, CT/MR simulation, image co-registration, contouring target volumes and organs at risk, radiation delivery techniques including proton therapy). The need for sedation for young children undergoing radiation therapy, both during the planning and the treatment itself, is detailed. Special radiation techniques frequently used for the treatment of CNS malignancies, including radiosurgery and craniospinal irradiation, are described. This includes a brief summary of the history of radiosurgery, the different devices currently used for this technique, and clinical indications. Craniospinal irradiation is a technically challenging radiation treatment; its planning and delivery are summarized. Proton therapy, with current evidence and dosimetric benefits, is also discussed. Re-irradiation can also be considered in selected cases of recurrent CNS malignancies, and indications are addressed. As well, a discussion of the most common acute toxicities experienced by patients during radiation therapy, and management of these side effects, is included. The somnolence syndrome, an early-delayed effect sometimes encountered, is also described.