PATTERN OF RECURRENCE OF MEDULLOBLASTOMA AFTER LOW-DOSE CRANIOSPINAL RADIOTHERAPY

Purpose: We retrospectively evaluated relapse of medulloblastoma after low- or high-dose craniospinal radiotherapy, and after conventional or hyperfractionated posterior fossa irradiation. Methods and Materials: Ninety-two pediatric patients were treated postoperatively since 1970 at the University of California, San Francisco. Until 1989, we employed conventional fractionation with low (less than or equal to 30 Gy) or high-dose craniospinal fields and low-dose (less than or equal to 56 Gy) posterior fossa boosts. Recently, hyperfractionation delivered low- or high-dose to the craniospinal axis and high-dose to the posterior fossa. Most patients treated after 1979 received chemotherapy. Results: Median follow-up was 70 months. Five-year disease-free survival was 36% (22% for poor-risk vs. 59% for good-risk patients). Five-year overall survival was 52% (43% for poor vs. 68% for good-risk). Neither the dose to the posterior fossa nor the craniospinal axis was statistically related to recurrence. Failure in the posterior fossa occurred despite boosts greater than 56 Gy. Females, over the age of 6 years, had significantly better relapse-free survival than males of the same age. Six of the 54 patients who relapsed were long-term survivors. Conclusions: Low-dose craniospinal radiotherapy, where the majority of patients received chemotherapy, was not associated with increased failure. High-dose posterior fossa hyperfractionation did not improve control. Long-term survival was noted in a number of patients after relapse. We recommend 60 Gy or greater with conventional fractions to the primary area, and continued study of low-dose craniospinal irradiation with adjuvant chemotherapy.