RADT-26. PATTERNS OF RECURRENCE IN PATIENTS TREATED WITH RE-IRRADIATION FOR RECURRENT HIGH-GRADE GLIOMA

Abstract Purpose/Objective(s) Re-irradiation (ReRT) is often used to treat recurrent high grade glioma (HGG). There limited literature regarding the patterns of recurrence following ReRT, which was investigated in current study. Materials/METHODS Patients with available radiation (RT) contours, dosimetry, and imaging-based evidence were included retrospective All patients treated fractionated RT using conformal technique. Recurrence documented as per decision tumor board based on imaging magnetic resonance (MRI) or Flouroethyl-L-Tyrosine (FET) positron emission tomography (PET), registered planning CT. Failure classified in-field, marginal, out-field decided by >50% volume within 95%, 20-95%, outside 20% isodose lines, respectively. RESULTS Study population 37 median dose 54 Gy (range 50.4-54 Gy). Before 92% had undergone surgery (biopsy 3, gross total resection 9, subtotal 22), 62% received concurrent chemo 49% maintenance chemotherapy. Median time 9 months (7-16 months, 10 8 respectively for in-field marginal/out-field recurrence). In-field, seen 24 (65%), (27%), 3 (8%), mapping done MRI, PET, both 27, 7, Of recurrence, 16 disease clinical target volume, 2 leptomeningeal dissemination (1 majority 1 marginal failure addition metastatic disease). CONCLUSION Following ReRT HGG, region, suggesting use conservative volumes. Future studies are required feasibility dose-escalation improve control rates, particularly long intervals from first course RT.