MEDULLOBLASTOMA WITH BRAIN-STEM INVOLVEMENT - THE IMPACT OF GROSS TOTAL RESECTION ON OUTCOME

We studied the impact of gross total resection on progression-free sur vival (PFS) and postoperative morbidity in 40 children with locally ad vanced medulloblastoma characterized by tumor invading the brain stem. These patients represented 40% of children treated for newly diagnose d medulloblastoma at a pediatric oncology center over a 10-year period . Al patients underwent aggressive initial surgical resection. Review of surgical and neuroimaging findings documented gross total resection in 13 cases, near-total resection (<1.5 cm(2) residual tumor on imagi ng) in 14 cases, and subtotal resection (>than 50% resection with grea ter than or equal to 1.5 cm(2) residual) in 13 cases. Overall, 85% of patients had a >90% resection. Subsequent therapy comprised craniospin al irradiation in all cases and chemotherapy on institutional or coope rative group protocols in 35 cases. At a median follow-up of 4 years, postirradiation PFS is 61% (SE = 10%). There was no difference in PFS for patients who underwent gross total resection compared to those wit h any detectable residual tumor (p>0.70). The posterior fossa syndrome occurred in 25% of cases, and had no apparent relationship to the ext ent of resection (p>0.5, exact test). In this series, true gross total resection was not associated with a PFS advantage when compared to st rictly defined near-total and subtotal resection. Although there was n o operative mortality, the frequency of the posterior fossa syndrome i s of concern and emphasizes the need for careful consideration of the risk/benefit ratio in the surgical approach to this subgroup of patien ts.