Radiotherapy in Medulloblastoma

Abstract

Medulloblastoma is a relatively radiosensitive tumor, and combined treatment approaches such as radiotherapy, surgery, and chemotherapy provide a better outcome. Patients with medulloblastoma are at risk of spread through the cerebrospinal fluid to the brain and spinal cord; therefore, craniospinal irradiation (CSI) represents the standard for care. CSI is typically a complex technique where two opposite cranial fields are joined with a posterior spinal field, and the patient is placed in a prone position. One major disadvantage of this technique is that large areas of healthy tissue are irradiated with high doses. To overcome the disadvantages of conventional radiotherapy, novel radiation technologies have been developed for large and complex targets, like 3-dimensional conformal radiotherapy, intensity-modulated radiotherapy, helical tomotherapy, arc therapy, and proton therapy. The traditional postsurgical treatment for standard-risk patients has been radiation therapy consisting of 36 Gy to the craniospinal axis together with a boost of 18-20 Gy to the posterior fossa (total dose 54-56 Gy). Since intellectual outcome with these approaches remains suboptimal, investigators have considered new ways to further reduce the side effects of radiotherapy, combining treatment with chemotherapy, reducing the neuraxis dose (for average risk disease, 23.4 Gy to craniospinal axis with posterior fossa boost of 30.6 Gy), and using more conformal techniques. CSI is complex and should be applied in centers with adequate experience both in technique and scheduling of clinical follow-up to monitor later side effects.