Treatment Responses in Adult Brainstem Gliomas with IDH1/2 Mutations (P3.127)

OBJECTIVE: Report clinical presentation and treatment responses for two adults with IDH-mutated brainstem gliomas. BACKGROUND: Adult brainstem gliomas are rare tumors and as a result, treatment protocols have not been established. DESIGN/METHODS: We reviewed clinical, radiographic, pathologic and treatment response characteristics for two adult patients with IDH-mutated brainstem gliomas. RESULTS: Case 1 is a 42-year-old man who presented with a one year history of right 6th and 7th cranial nerve palsies. MRI showed a non-enhancing mass in the right pons, measuring 3.1x2.9x2.2 cm. He underwent stereotactic biopsy which revealed a WHO grade III anaplastic oligodendroglioma with codeletion of 1p36 and 19q13 and IDH2 R172M mutation. He was treated with concurrent radiation and temozolomide for 6 weeks and showed partial radiographic response. He remains clinically and radiographically stable following 12 cycles of adjuvant temozolomide. Case 2 is a 48-year-old man with a six month history of worsening exertional headache. MRI showed a mildly-enhancing diffuse pontine lesion measuring 6.6x3.4x4.8 cm. Stereotactic biopsy revealed a WHO grade II astrocytoma with IDH1 R132C mutation and MGMT promoter methylation was present. There was deletion of 19q, but 1p remained intact. He received 5400 cGy over 6 weeks and no chemotherapy. He has been clinically and radiographically stable for one year. CONCLUSIONS: Adult brainstem gliomas are uncommon and those with IDH1/2 mutations are exceedingly rare. There is no standardized protocol for treatment of these tumors in adults and current strategies are extrapolated from data on supratentorial tumors. Our series reports treatment response for two patients with brainstem glioma. Disclosure: Dr. Hodges has nothing to disclose. Dr. Malafronte has nothing to disclose. Dr. Skinner has nothing to disclose. Dr. Carter has nothing to disclose. Dr. Gilhooly has nothing to disclose. Dr. Theeler has nothing to disclose.