BRAF AND MEK DUAL INHIBITORS THERAPY IN RECURRENT OR ANAPLASTIC PLEOMORPHIC XANTHOASTROCYTOMA (PXA)

Abstract BACKGROUND AND OBJECTIVE Recurrent and anaplastic pleomorphic xanthoastrocytoma (PXA) tumors are challenging to treat due to their rarity and lack of management consensus. About 80% of PXAs harbor BRAF gene mutation. Although the development of BRAF inhibitors has dramatically improved the outcomes for patients with BRAF V600E mutant tumors, resistance develops in the majority of cases. We hypothesize that dual BRAF/MEK inhibitors therapy can improve tumor control and patient survival without added toxicity. METHODS Medical records from 2010 to 2021 in Memorial Hermann Texas Medical Center were reviewed. Patients diagnosed with PXA who received BRAF and/or MEK inhibitors therapies were identified. The data evaluated included age, sex, treatment received, side effects, and outcomes, as well as results from blood tests, pathology, next generation sequencing and MRI. Side effects were evaluated according to the CTCAE Version 5.0. RESULTS Five patients with recurrent or anaplastic PXA were identified. The median age at diagnosis was 22 years old (range 14-66 years old), with 60% male, and 60% grade III. All patients received BRAF/MEK dual inhibitors therapy at various stages of PXA treatment. The median follow-up was 72 months (range 17-108 months). One patient (66 years old) experienced short-term disease stability for 5 months and who died from tumor related brain hemorrhage while off therapy for 9 months. Four patients experienced long-term disease control (17, 22, 94, 108 months, respectively) while three of them remain on dual therapy and one patient died from systemic PXA progression. Dual BRAF/MEK inhibitors were well tolerated with only grade 1-2 adverse effects (AE) including skin rash, fatigue, mild abdominal discomfort, diarrhea. No grade III-V AE were detected. CONCLUSION BRAF/MEK dual inhibitor can provide potential clinical benefit to PXA patients with BRAF mutations. Our study supports the concurrent use of BRAF/MEK inhibitors for best tumor control without unexpected AE.