Study definitions
High-education status was defined as more than 9 years of education. Distance from tertiary cancer center was separated into two groups: close to INCA (≤ 40 km) and far from INCA (>40km). The histopathologic diagnoses were divided into groups: classic, anaplastic/large cell, desmoplastic/extensive nodularity, and not otherwise specified (NOS). The extent of surgical resection was categorized into two major groups according to the surgeon’s report: gross total resection (GTR) and subtotal resection (STR) or biopsy, when there was remaining tumor. Patients were classified as high-risk (HR) whether they were metastatic, had residual tumor >1.5cm2 on post-operative MRI. Patients with localized disease, with residual tumor <1.5cm2 or GTR and above 3 years were classified as Standard Risk (SR). Diagnosis date was defined by the date of primary surgery.
Between april/1997 and march/2000, patients received Pre-irradiation Chemotherapy regimen which consisted of 3 cycles of ifosfamide/etoposide and 3 cycles of cisplatin/vincristine, with radiation therapy by week 15, with 36Gy CSI plus boost to posterior fossa). After march/2000, COGA9961 regimen(20) became the standard treatment for children above 3 years. Children were treated with upfront radiation therapy (23.4 Gy CSI for SR and 36 Gy CSI for HR with concomitant vincristine plus boost up to 54Gy to posterior fossa and maintenance chemotherapy with 8 cycles of cisplatin, vincristine and lomustine).