CNSC-20. MGMT PROMOTER METHYLATED HIGH GRADE GLIOMA WITH DISTANT RECURRENCE AND STABLE ORIGINAL TUMOR SITE: CASE SERIES

Abstract

Abstract Recurrence pattern in high grade glioma is classified as local and distant recurrence based on distance from original resection cavity and radiation field. We report the first series of three cases of O6-methylguanine-DNA methyltransferase (MGMT) promoter methylated high grade glioma with distant recurrence without local recurrence throughout the disease course. Patient 1: 65 year-old female with WHO grade 4 glioblastoma, isocitrate dehydrogenase enzyme (IDH) wild type (WT), MGMT methylated. She underwent gross total resection followed by Stupp protocol. Postoperative ischemic volume was < 1 ml. Distant recurrence occurred 4 months after completion of Stupp protocol. Patient 2: 55 year-old male with WHO grade 4 glioblastoma, IDH wild type, MGMT methylated. He underwent gross total resection followed by Stupp protocol. Postoperative ischemic volume was 18 ml. Distant recurrence occurred 5 months after completion of Stupp protocol. Patient 3: 31 year-old male with WHO grade 4 astrocytoma, IDH mutant, MGMT promoter methylated. He underwent gross total resection followed by Stupp protocol. Postoperative ischemic volume was 2 ml. Distant recurrence occurred 10 months after completion of Stupp protocol. Distant recurrence is more common in MGMT promoter methylated tumors. All 3 patients in our case series had poor outcomes after distant recurrence without local recurrence at the original tumor site. This observation indicates good local control in MGMT promoter methylated high grade glioma with current standard treatment. For one patient, next generation sequencing (NGS) was available for both original and recurrent tumor and did not reveal any major differences in the genetics of original tumor and distant recurrent tumor other than temozolomide induced high tumor mutational burden in the distant recurrent tumor. Understanding risk factors for distant recurrence in MGMT promoter methylated high grade gliomas and investigating correlations between recurrences will help plan therapeutic strategies to prevent distant recurrence and improve outcomes.