Medulloblastoma: are we overtreating?

Modern advances in the concept and the techniques of megavoltage radiation therapy have revolutionized the treatment of medulloblastoma. Five-year survivals of 50 to 70 percent are achieved by craniospinalaxis irradiation with a boost to the posterior fossa. However, the price paid by the long-term survivors is significant. Sequelae include growth retardation, thyroid deficiency and anomalies, marrow suppression, gonadal irradiation, IQ and psychological deterioration, immunological alterations, second malignancies, and pituitary hormonal deficiencies.The literature is reviewed in terms of these sequelae and analyzed to determine optimal therapeutic doses. Although the authors agree with the doses used to treat the posterior fossa, the current doses recommended to eradicate the microscopic disease in the rest of the neuroaxis appear excessive; a lesser dose can be as effective and may decrease the rate and severity of complications.The authors believe that there is enough evidence to initiate a randomized, multi-institutional clinical trial using 20 to 25 Gy to the neuraxis (other than the posterior fossa) in one of the arms, especially when there is no evidence of tumor outside the posterior fossa.Electron beam radiation of the spinal component can decrease the dose to some of the normal structures and prevent some of the long-term sequelae.