P14.74 Remarkable response to Combined BRAF and MEK Inhibitors in two Adults with leptomeningeal carcinomatosis secondary to Pleomorphic Xantoastrocytoma grade II with BRAFv600E mutation

Abstract

Abstract BACKGROUND Several cancers with the BRAF V600E mutations have been successfully treated with targeted therapy. Pleomorphic xanthoastrocytoma (PXA) is a rare brain tumor, with an incidence of 0.07cases per 100,000. The BRAFV600 mutation is present in 38–60% of PXA. Typical treatment is gross total resection, followed by radiotherapy and cytotoxic chemotherapy at recurrence MATERIAL AND METHODS Two cases are described. RESULTS The first case is a 37 old man with a left temporal lobe lesion who underwent a craniotomy with total tumor resection. Histological diagnosis was PXA WHO grade 2with BRAF V600E mutation.Five months after, MR imaging of his brain and spine showed tumor progression with extensive leptomeningeal disease. The patient received adjuvant brain and spinal radiotherapy Two weeks after, due to rapid clinical worsening he had a new brain and spinal MRI showing hydrocephalus and progression of the pachymeningeal-based masses and received an emergency ventricular -peritoneal shunt. Given the genetic analysis, the extent of disease and rapidity of the progression, BRAF and MEK inhibitors, dabrafenib (150 mg, twice daily) and trametinib (2 mg, daily) were started. Remarkably, within 2 week of initiating dual-targeted therapy, the patient experienced a dramatic improvement in consciousness and overall strength; brainand spinal MRI revealed initial reduction of the leptomenigeal enhacement and no evidence of progression of the intraparenchymal disease. The therapy was well-tolerated. Currently, after sixteen months,the patient remains on treatment with a consistent functional status improvement and no radiological evidence of disease progression. The second case is a 51 old women who developed leptomeningeal carcinomatosis seven year after resection of a frontal left PXA WHO grade 2 with BRAFv600E mutation. The patient had received brain radiotherapy five years after diagnosis and Cyber Knife for tumor progression. Ten months later MR imaging of his brain and spine showed tumor progression with extensive leptomeningeal disease, she was treated with temozolomide for 8 after clinical and radiological worsening she had a second surgery with resection of recurrent frontale left lesion Histopathology PXA WHO grade 2 with BRAF V600E mutation. She developed hydrocephalus, received an emergency ventricular -peritoneal shunt. BRAF and MEK inhibitors, dabrafenib (150 mg, twice daily) and trametinib (2 mg, daily) were started three months ago with initial clinical benefit CONCLUSION All patients with PXA should be tested for the BRAFV600 mutation, since, in these cases, targeted therapy with BRAF and MEK inhibitors seems to be a useful option for salvage treatment.