Concurrent chemotherapy and reduced-dose cranial spinal irradiation followed by conformal posterior fossa tumor bed boost for average-risk medulloblastoma: efficacy and patterns of failure.

PURPOSE: To review the efficacy and patterns of failure in average-risk medulloblastoma patients treated with concurrent chemotherapy and reduced-dose cranial spinal irradiation and a conformal tumor bed boost. METHODS AND MATERIALS: Thirty-three patients with average risk (defined as < or =1.5 cm(2) of residual tumor after resection, age >3 years, and no involvement of the cerebrospinal fluid or spine [M0]) medulloblastoma were diagnosed at our institution between January 1994 and December 2001. They were enrolled in an institutional pilot protocol consisting of concurrent chemotherapy (vincristine), reduced-dose cranial spinal irradiation (2340 cGy), a conformal primary tumor bed boost (3240 cGy), followed by eight cycles of chemotherapy (vincristine, cisplatin, and lomustine or cyclophosphamide). The median age at diagnosis of the 33 patients was 7 years (range, 3-21 years). The male/female patient ratio was 2.4:1. The median follow-up of the entire group was 37 months (range, 6-96 months), and the median follow-up of the survivors was 44 months (range, 10-96 months).
RESULTS: The 5-year estimated disease-free survival rate, as determined by Kaplan-Meier plots, was 86% (+/-12.6%, 95% confidence interval). The 5-year estimated disease-free posterior fossa control and primary tumor bed control rates were both 94% (+/-8.2%, 95% confidence interval). The patterns of failure included 2 patients with distant central nervous system failure only, 1 patient who developed local primary tumor bed failure, posterior fossa failure, and diffuse leptomeningeal spread simultaneously, and 1 patient with failure in the high-dose, primary tumor bed field. No patient experienced isolated posterior fossa failure outside the high-dose boost region.
CONCLUSION: The treatment of average-risk medulloblastoma with chemotherapy, reduced-dose cranial spinal irradiation, and a conformal tumor bed boost results in survival rates and local control rates comparable to those in contemporary studies. A reduction in the amount of posterior fossa treated to the high dose is possible. These results need to be corroborated in a large, cooperative group study.