P17.17.A WHAT IS THE BETTER THERAPEUTIC STRATEGY FOR DISTANT RECURRENT GLIOMA? OUTCOME AND PROGNOSTIC FACTORS EVALUATION IN A RETROSPECTIVE SERIES

Abstract

Abstract BACKGROUND Distant recurrent glioma is a rare condition. A possible correlation has been postulate with original tumor location in close proximity to the subventricular zone. Nevertheless, to date no data exist about treatment strategy, neither retrospective nor prospective studies, and a standard of care is missing. Several treatment options are available: surgery, systemic treatment (CHT), and radiation therapy (RT) alone or with concomitant chemotherapy. Aim of this retrospective analysis was to investigate outcome of patients (pts) with distant recurrent glioma treated with RT, with or without concomitant and/or adjuvant temozolomide chemotherapy. MATERIAL AND METHODS Adult pts with distant recurrent glioma have been evaluated. Histological diagnosis has been reclassified according to the 2021 WHO Classification of Central Nervous System tumors, and original tumor proximity to subventricular zone has been registered. Distant progression treatment strategies included RT alone, RT concurrent with CHT (RT-CHT), RT followed by CHT. For RT planning, target delineation was defined on simulation CT scan and brain MRI co-registered into the image workstation of Brainlab. RESULTS From 2015 to 2023, 35 distant recurrent glioma pts have been evaluated. Histological diagnosis was: glioblastoma (GBM) in 27 pts, astrocytoma grade 3 IDH-mutant in 6 pts, and astrocytoma grade 2 IDH-mutant in 2 pts. Location of primary tumor was in subventricular zone in all cases: 16 pts developed only distant recurrence, 19 pts both local and distant recurrence. Median interval time (IT) between diagnosis and distant recurrence was 22 months (range 5-49); 8 cases had distant recurrence within 12 months, 17 cases between 13 and 24 months, and 10 cases ≥ 24 months. Regarding treatment strategy, 10 pts (29%) received RT alone, 6 pts (17%) received RT-CHT, 11 (31%) received RT followed by sequential CHT, 8 (23%) received concurrent RT-CHT followed by sequential CHT. Median RT dose was 45 Gy in 15 fractions (range 30-50 Gy in 5-20fr). Median follow up time was 36months (range3-97). Median overall survival (OS) time, 6 months,1,2-year OS rates from diagnosis were 33 months (95% CI 30-36), 100%, 94.3%±3.92, 70.0%±7.9, respectively. Median OS time, 6 months,1,2-year OS rates from distant recurrence were 10 months (95% CI 7-12), 75.4%±7.6, 26.2%±7.9, 0.%. On univariate, and multivariate analysis, prognostic factors impacting OS were IT between diagnosis and first recurrence, and treatment performed. Indeed, median OS time were 6 months (95% CI 2-10) for IT ≤ 1year (P= 0.0363), 17 months (95% CI 8-12), 10 months (95% CI 7-12), 6 months (95% CI 8-12) for RT alone, RT and concurrent RT-CHT followed by sequential CHT, concurrent RT-CHT without sequential CHT, respectively (P < 0.0001). CONCLUSION Our results suggest that RT alone could be a feasible and effective treatment option for distant recurrent glioma.