INNV-30. RESPONSE WITH COMBINED DABRAFENIB AND TRAMETINIB AFTER BRAF INHIBITOR FAILURE IN BRAF-MUTATED GLIOBLASTOMA: A CASE REPORT

Abstract Glioblastoma (GBM) carries a poor prognosis despite aggressive multimodality therapy. Oncogenic BRAF mutations are present in < 2% of GBM, along with other glioma types (ganglioglioma, pleomorphic xanthoastrocytoma). Although oral inhibitors of the oncogenic BRAFv600 kinase have demonstrated some efficacy in GBM, several mechanisms mediating resistance to BRAF inhibitors through MAPK reactivation have been described. BRAF inhibitor monotherapy is also associated with an increased risk for hyperproliferative skin lesions. We present a case of a 44-year-old man who initially presented with headaches and seizures and was diagnosed with a left temporal, MGMT unmethylated, BRAF V600E mutant GBM. He underwent gross total resection followed by radiation therapy with concurrent temozolomide, followed by 9 cycles of adjuvant temozolomide. He presented with progression of disease (POD) and subsequently failed treatment with carboplatin after two cycles (first recurrence). He had a repeat resection, and was enrolled in a clinical trial of autologous dendritic cell vaccine and presented with POD after 10 months on this treatment (second recurrence). He was started on another clinical trial of BRAF inhibitor, achieving partial response but developed POD after 7 months on this therapy (third recurrence). He was started on BRAF inhibitor dabrafenib and MEK inhibitor trametinib (D+T), achieving complete response. At the time of this report, 8 months after initiating treatment, the patient remains clinically stable with MRI showing CR. To our knowledge, this is the first report of clinical and radiographic response to combined D+T after BRAF inhibitor failure in BRAF-mutated glioblastoma. Several ongoing trials (NCT01677741, NCT01748149, NCT02124772, NCT02684058, NCT02285439), will elucidate the precise role of these drugs as single agent and in combination in pediatric and adult brain tumors.