BIOM-44. MAGNETIC RESONANCE IMAGING MAPPING OF BRAIN TUMOR BURDEN TO EVALUATE RESPONSE TO PULSED LOW-DOSE-RATE RADIOTHERAPY FOLLOWING RESECTION OF GLIOBLASTOMA MULTIFORME: A 4-PATIENT CASE SERIES

Abstract BACKGROUND Pulsed low-dose-rate radiotherapy (pLDR) is an accepted reirradiation technique for recurrent glioma, but its upfront use, concurrent with temozolomide (TMZ) following resection of high-grade glioma currently under investigation. Evaluating the response to radiation can be challenging and there limited data on expected rates pseudoprogression pLDR. Standard magnetic resonance imaging (MRI) has limitations in differentiating from tumor progression, sometimes necessitating surgery pathologic confirmation. Advanced MRI used create fractional burden (FTB) maps that spatially distinguish active treatment-related effect (pseudoprogression), perhaps providing a more reliable biomarker absence additional surgery. METHODS We performed retrospective chart review report responses four patients glioblastoma pLDR TMZ resection. Each patient received advanced surveillance redo Tumor pathology included IDH-wild type (n = 4) O6-methylguanine-DNA methyltransferase (MGMT) methylated 1) tumors. RESULTS The median age was 57.5 years (range 55-60 years) all were male. One experienced mortality another transitioned hospice. In cases, concerns progression postcontrast MRI. Pathologic diagnosis revealed either treatment 2) or 2). FTB predominantly indicative lesion volumes being comprised 3) 1). From three former category, fraction enhancing volume vascular 6.4% 1.8-6.8%). CONCLUSION This case series provides insight into demonstrates capacity mapping this population.