HGG-35. PEDIATRIC PLEOMORPHIC XANTHOASTROCYTOMA WITH ANAPLASIA TREATED WITH SURGERY AND ADJUVANT CHEMOTHERAPY: A CASE SERIES OF 3 LONG-TERM SURVIVORS

OBJECTIVE: Pleomorphic xanthoastrocytoma (PXA) with anaplasia is a rare histological subtype of central nervous system astrocytoma and generally treated as high grade gliomas. The optimal extent of therapy required is unknown. Here we report on 3 pediatric cases of PXA with anaplasia. We also describe molecular features and methylation profile of PXA with anaplasia compared to age-matched PXA without anaplasia. METHODS: Our institutional database was queried for cases of PXA since 1998 and 3 cases with anaplasia were identified and records reviewed. RESULTS: 2/3 patients were male and all were aged 12 at diagnosis. All underwent a gross total resection (GTR), where the diagnosis of PXA with anaplasia was made. Immunohistochemistry demonstrated that two cases were BRAF V600E positive and two were CD34 positive. Methylation profiling revealed unique pattern of CpG methylation/unmethylation. All patients underwent 5400cGy radiation to the surgical bed. 2/3 patients received concurrent temozolamide with radiation followed by maintenance chemotherapy with temozolamide and lomustine for 6 cycles as per the Children’s Oncology Group Protocol ACNS0423. These two patients had a continued complete response. The third patient received temozolamide following radiation and subsequently had recurrent disease at the end of treatment and went on to have a re-resection GTR and achieved complete response after 6 cycles of lomustine, vincristine and procarbazine. All are alive with no evidence of disease at more than 2 years post treatment completion (OS=100%,EFS=67%). CONCLUSIONS: This rare pediatric tumor is not well understood. The genetic landscape may be informative for optimizing treatment and prognosis.