MB-23: RECURRENT SHH/TP53 MUTANT MEDULLOBLASTOMA TREATED WITH A COMBINATION OF LITHIUM AND RADIATION THERAPY

INTRODUCTION: TP53 mutations remain a poor prognotic factor and account for a high proportion of the treatment failure in SHH subgroup medulloblatoma. Poor survival of patients with P53 mutant medulloblastoma may be related to radiation/chemotherapy resistance. Lithium, an activator of the WNT pathway, sensitizes TP53 mutant medulloblastoma to radiation. CASE REPORT: a 12-yo boy presented with left localized hemispheric medulloblastoma. After a complete excision of the tumour he was randomized and treated according to COG ACNS0331 and received a standard-dose craniospinal radiation with a boost to the entire posterior fossa, followed by maintenance chemotherapy. Patient was considered in complete remission. 15 months post-end of treatment, MRI showed a local recurrence. After 2 cycles of temozolomide, irinotecan and bevacizumab chemotherapy, patient had tumor progression. He then underwent a complete resection of the tumour. Pathology showed anaplastic type, SHH/TP53 mutant medulloblastoma. Due to the expected poor survival and the lack of known and consensual curative treatment, the patient was treated with a combination of therapeutic dose of lithium and focal radiation therapy to a dose of 54 Gy. One year later, the patient remains asymptomatic and, in complete remission. CONCLUSION: Lithium combined to radiation therapy may represent an interesting therapeutic avenue for higher risk groups of medulloblastoma in a context of a pilot study.