Intellectual outcome after reduced-dose radiation therapy plus adjuvant chemotherapy for medulloblastoma: a Children's Cancer Group study

PURPOSE: To investigate the intellectual outcomes of children with medulloblastomas/primitive neuroectodermal tumors (MB/PNET) treated with reduced-dose craniospinal radiotherapy (RT) plus adjuvant chemotherapy. PATIENTS AND METHODS: Forty-three children with average-risk posterior fossa MB/PNETs underwent longitudinal intelligence testing. All had been treated with a reduced-dose craniospinal RT regimen (23.4 Gy to the neuraxis, 32.4-Gy boost to the posterior fossa) and adjuvant chemotherapy. RESULTS: The estimated rate of change from baseline was significant for Full Scale Intelligence Quotient (FSIQ), Verbal IQ (VIQ), and Nonverbal IQ (NVIQ) (P < .001 for all three outcomes). The rate of change was estimated to be −4.3 FSIQ points per year, −4.2 VIQ points per year, and −4.0 NVIQ points per year. Females were more subject to VIQ decline than were males (P = .008), and young children (< 7 years of age) were more negatively affected than were older children, with a significant decline in NVIQ (P = .016). Finally, patients with higher baseline evaluations suffered greater declines in IQ than did those with lower baseline scores. CONCLUSION: This study represents the largest series of patients with average-risk MB/PNETs treated with a combination of reduced-dose RT and adjuvant chemotherapy whose intellectual development has been followed prospectively. Intellectual loss was substantial but suggestive of some degree of intellectual preservation compared with effects associated with conventional RT doses. However, this conclusion remains provisional, pending further research.