Abstract BACKGROUND: Because medulloblastoma (MB) is rare in adults, the few studies on this condition have been retrospective, and the follow-up has tended to be short. Furthermore, the different therapeutic strategies used in these patients has made it difficult to assess survival rates and prognostic factors. METHODS: In 1989, a prospective Phase II trial was initiated to evaluate the efficacy of treatment for adults with MB. Patients were staged completely with a neuroradiologic examination of the brain and neuroaxis and by cerebrospinal fluid cytology, according to Chang's staging system. Low-risk patients received radiotherapy alone, whereas high-risk patients received 2 cycles of upfront chemotherapy followed by radiotherapy and adjuvant chemotherapy. The current article reports on the long-term results from that trial. RESULTS: After a median follow up of 7.6 years, among a total of 36 adults with MB, the overall progression-free survival (PFS) and overall survival (OS) rates at 5 years were 72% and 75%, respectively. In low-risk patients, the 5-year PFS rate was 80%, and the 5-year OS rate was 80%; in high-risk patients, the 5-year PFS rate was 69%, and the 5-year OS rate was 73%. CONCLUSIONS: In adult patients with MB, long-term follow-up was essential for evaluating the real impact of treatments. Low-risk and high-risk patients did not differ significantly in terms of PFS or OS.