RARE-18. CLINICAL EXPERIENCE OF DABRAFENIB IN COMBINATION WITH TRAMETINIB TREATMENT FOR ANAPLASTIC PXA CASES

Abstract

Abstract Anaplastic PXA is classed as grade III tumor because of its aggressive behavior in 2016 WHO classification. Typical treatment of PXA is gross total resection followed by radiotherapy and cytotoxic chemotherapy at recurrence. Despite aggressive behavior of anaplastic PXA, there is some evidence for the use of BRAF inhibitors in BRAF V600 mutant PXA. We report two cases of successful treatment with BRAF-MEK inhibitor combination therapy (dabrafenib plus trametinib). A 19 year-old man initially diagnosed as PXA for rt temporal tumor. Subtotal removal and following 30Gy radiation was performed. After eight years, the recurrent tumor was removed subtotally and diagnosed as anaplastic PXA. Residual tumor and distant metastasis region were completely disappeared by Dabrafenib-Trametinib therapy. Tumor was diagnosed as BRAF V600 mutant and TERT wt. A 30 year-old female initially diagnosed as PXA for rt temporal cystic tumor. She was treated with subtotal removal followed by stereotactic radiosurgery. Instead of Gd-total removal, tumor recurred six times. Chemotherapy with alkyl-agent did not respond. Tumor at first surgery was diagnosed as grade II PXA. Tissues collected after SRS showed malignant feature and diagnosed as anaplastic PXA. All five specimens showed BRAF V600 mutation and additional TERT mutation was confirmed after SRS treatment. She showed paraparesis because of thoracic metastases then Dabrafenib-Trametinib therapy was started. Thoracic tumor showed PR and no remarkable recurrence in intracranial region for more than eight months, so far. BRAF and MEK inhibitor combination treatment are thought to have potential for BRAF V600 mutant NSCLC and melanoma. Anaplastic PXA with BRAF V600 mutation could be another target for the treatment.