Adult medulloblastoma: Prognostic factors and patterns of relapse

OBJECTIVE: To determine the patterns of relapse and the prognostic factors for adult medulloblastomas treated in the magnetic resonance imaging era. METHODS: Between 1986 and 1996, 32 adult patients (age, greater than or equ al to 16 yr) with medulloblastomas confined to the craniospinal axis were t reated in our institutions. Twenty cases involved classic histological feat ures and 12 involved the desmoplastic variant. The Chang staging distributi on was as follows: T1, 2; T2, 17; T3, 10; T4, 3; M0, 24; M1, 1; M2, 4; M3, 3. Brainstem invasion was present in nine patients. Lesions were midline in 13 cases and lateral in 19. Resection was complete in 17 cases, subtotal i n 6, and partial in 5, with biopsy only in 4 cases. All patients received p ostoperative radiotherapy, with median doses of 36 Cy to the entire cranios pinal axis and 55 Cy to the posterior fossa. Twenty-four patients received chemotherapy (20 before radiotherapy, 3 after radiotherapy, and 1 before an d after radiotherapy). RESULTS: With a median follow-up period of 5.4 years, 17 patients experienc ed recurrences. At 5 and 8 years, overall survival rates were 83 and 45% an d disease-free survival rates were 57 and 40%, respectively. The 5- and 8-y ear posterior fossa control rates were 67 and 59%, respectively. Twenty-nin e percent of all relapses occurred more than 5 years after treatment. The p osterior fossa was the most common site of relapses. In univariate analyses , factors adversely affecting posterior fossa control were less than comple te resection (P < 0.001), the presence of brainstem invasion (P = 0.02), an d the use of chemotherapy (P = 0.03). The overall radiotherapy duration was marginally significant in predicting posterior fossa control, with 5-year posterior fossa control rates of 81 and 49% for durations of less than 48 d ays and 48 days or more, respectively (P = 0.06). In a multivariate analysi s, complete resection was predictive of improved posterior fossa control (P = 0.02) and disease-free survival (P = 0.02) rates, Of the eight low-risk patients who received radiotherapy alone, three experienced recurrences in the bone as the only site of relapse. CONCLUSION: Late relapse is common among adult patients with medulloblastom as, and long-term follow-up monitoring is important. Because of the high ri sk of systemic failure among the low-risk patients treated with radiotherap y alone, the role of chemotherapy for this group of patients needs to be fu rther investigated. Complete resection, the absence of brainstem invasion, and an overall radiotherapy duration of less than 48 days are important pro gnostic factors.