7– 9 The primary objective of the Pediatric Oncology Group (POG) 9031 multi-institutional study was to compare the clinical outcome of treating high-risk medulloblastoma patients with either preirradiation or postirradiation chemotherapy, with both groups receiving identical consolidation chemotherapy. One strategy has been to give preirradiation chemotherapy, the results of which have been mixed. To improve survival for high-risk medulloblastoma, a number of different strategies have been investigated that attempt to combine chemotherapy with radiation therapy in an optimized manner. More recent trials treating standard-risk medulloblastoma using reduced-dose CSI and adjuvant chemotherapy have produced EFS rates of 81% to 86%. 6– 11 Packer et al 12 later established the value of chemotherapy in the standard-risk patient, for whom the dose of CSI could be lowered to 23.4 Gy in the setting of similar adjuvant chemotherapy without compromising survivability. Current event-free survival (EFS) rates for high-risk patients using full-dose CSI with or without the addition of chemotherapy range from 30% to 74%. In the 1970s, randomized trials conducted by the Children's Cancer Group and the International Society of Pediatric Oncology demonstrated improved survival for the high-risk patient when incorporating adjuvant chemotherapy, 4, 5 the results of which Packer et al 6 improved on by adding cisplatin to lomustine and vincristine. Since medulloblastoma was first described in 1925 by Bailey and Cushing, the futility of surgical resection alone has been recognized, and it was only after the use of postsurgical craniospinal irradiation (CSI) in the 1960s that significant survivability was reported. Patients greater than 3 years of age are stratified into risk groups based on the extent of disease beyond the original tumor site, as summarized in the M stage of the Chang staging system, with M1 or greater and residual tumor size after surgery of greater than 1.5 cm 3 considered high risk.

1, 2 For the purposes of treatment, patients are divided by age-less than or greater than 3 years of age-with these groups further subdivided into standard-risk and high-risk groups. Medulloblastoma is the most common pediatric brain malignancy, with approximately 540 new patients diagnosed in the United States each year.

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