POSTOPERATIVE RADIATIONTHERAPY OF MEDULLOBLASTOMA - IMPACT OF RADIATION QUALITY ON TREATMENT OUTCOME

Between 1975 and 1991, 40 patients with newly diagnosed medulloblastom a of the posterior fossa were treated at the authors' institutions. Af ter aggressive surgical resection 39/40 patients (98%) received cranio spinal radiation therapy (RT), including a local boost. A group of 29 patients was treated with adjuvant chemotherapy. The estimated overall 5-year survival and 5-year relapse-free survival (RFS) probabilities were 75% and 65%, respectively. The 5-year survival was significantly prolonged for patients treated after 1981 as compared to those treated between 1975 and 1980 (80% vs 64%, p =.02). However, multivariate ana lysis identified the adequate coverage of the target volume by externa l RT as the only significant variable (p =.0031). The extent of resect ion, stage according to Chang, radiation dose to the posterior fossa ( <55 Gy vs greater than or equal to 55 Gy) and the use of chemotherapy did not significantly influence survival and RFS. The initial site of recurrence was the posterior fossa with or without disseminated centra l nervous system (CNS) disease in 5 patients, the CNS without posterio r fossa in 4 patients, and the bone marrow in 2 patients. An isolated frontal relapse occurred in 1 patient. We conclude that quality contro l of RT plays a decisive role in the long-term outcome of patients wit h medulloblastoma.