MB-43: REDUCED DOSE CRANIOSPINAL IRRADIATION (CSI) IS FEASIBLE FOR STANDARD RISK ADULT MEDULLOBLASTOMA (MBL) PATIENTS SIMILARLY TO PEDIATRIC POPULATION

MBL, the most common malignant pediatric brain tumor, represents 1% of adult brain tumors. Recent molecular classification suggests that MBL is not a similar disease in children and adults. For standard risk pediatric medulloblastomas current therapy includes CSI at reduced doses (23.4Gy) associated with chemotherapy. Most same stage adult patients still receive 36Gy of CSI. Hence the adoption of 23.4Gy together with chemotherapy(CT), also for older patients in some institutions, is worthwhile reporting. The series of adults, treated according to the HIT protocol generated a 73% 5-year PFS {Friedrich, Eur J Cancer 2013} that constitutes the best data. We gathered M0 medulloblastomas with no/minimal post-surgical residues and no biological negative factor, from 1999 to 2015. Thirty were adults (median age 26,18-48 years; median f-up 48 months,5-192) and 47 children (median age 9 years; median f-up 45 months,57-110). All had received 23.4Gy CSI plus posterior fossa/tumor bed boost and chemotherapy: pre-RT carbo/VPx2 courses or 8-in-onex2 courses (10 adults) and post-RT CT (carbo/VPx2 courses in 11 and 8-in-onex2 courses in 2 adults; CDDP/VCR/CCNUx8courses in children). 5-year PFS and OS were respectively 83 ± 9% and 94 ± 6% for adults, versus 92 ± 5% and 100% for children (p ns); Median progression time were 53 versus 40 months for older versus younger. Relapses were local (3), local + CSF (1) for adults versus local (1) and disseminated (2) for children. These combined series present comparable – or even better – results than those after high CSI doses both in adults and children highlighting the need for treatment redefinition in adults.