Radiation therapy

Radiation therapy to the primary tumor site is usually in the range of 54 Gy to 55.8 Gy.[94] In most instances, this therapy is given with a margin of 1 cm to 2 cm around the primary tumor site, preferably by conformal techniques.[94] Reducing boost volumes for the whole posterior fossa and to the tumor bed plus margins did not compromise outcomes in average-risk patients in the Children's Oncology Group (COG) ACNS0331 (NCT00085735) study.[59][Level of evidence A1] For all medulloblastomas in children older than 3 or 4 years at diagnosis, craniospinal radiation therapy is given at doses ranging between 23.4 Gy and 36 Gy, depending on risk factors such as extent of disease at diagnosis. A prospective phase II toxicity study of proton radiation therapy [95] and a retrospective efficacy report of protons versus photons for medulloblastoma [96] demonstrated equivalent outcomes for PFS, overall survival (OS), patterns of relapse, and delayed toxic effects. A retrospective study of 84 children who received either proton (n = 38) or photon (n = 46) radiation therapy demonstrated similar rates of grade 3 and grade 4 ototoxicity despite low mean cochlear doses in children who received proton radiation therapy, suggesting that other factors (e.g. cisplatin, initial tumor location in relationship to the vestibulocochlear nerve [eighth cranial nerve]) contribute to ototoxicity.[97] The comparative outcomes of these treatment technologies are under investigation.

Chemotherapy is usually administered during and after radiation therapy.

For children younger than 3 years, efforts are made to omit or delay radiation therapy, given the profound impact of radiation at this age. Children of all ages are susceptible to the adverse effects of radiation on brain development. Debilitating effects on neurocognitive development, growth, and endocrine function have been frequently observed, especially in younger children.[98-102]