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 o r hyperfractionated posterior fossa irradiation. Methods and Materials : Ninety-two pediatric patients were treated postoperatively since 197 0 at the University of California, San Francisco. Until 1989, we emplo yed conventional fractionation with low (less than or equal to 30 Gy) or high-dose craniospinal fields and low-dose (less than or equal to 5 6 Gy) posterior fossa boosts. Recently, hyperfractionation delivered l ow- or high-dose to the craniospinal axis and high-dose to the posteri or fossa. Most patients treated after 1979 received chemotherapy. Resu lts: Median follow-up was 70 months. Five-year disease-free survival w as 36% (22% for poor-risk vs. 59% for good-risk patients). Five-year o verall survival was 52% (43% for poor vs. 68% for good-risk). Neither the dose to the posterior fossa nor the craniospinal axis was statisti cally related to recurrence. Failure in the posterior fossa occurred d espite boosts greater than 56 Gy. Females, over the age of 6 years, ha d significantly better relapse-free survival than males of the same ag e. Six of the 54 patients who relapsed were long-term survivors. Concl usions: Low-dose craniospinal radiotherapy, where the majority of pati ents 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. W e recommend 60 Gy or greater with conventional fractions to the primar y area, and continued study of low-dose craniospinal irradiation with adjuvant chemotherapy.