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VIDEO DOI: https://doi.org/10.48448/z1yp-jw02

poster

AMA Research Challenge 2024

November 07, 2024

Virtual only, United States

The Patterns of Failure and Prognostic Impact of Tumor Location in Patients Undergoing Reirradiation for Glioblastoma

Background RTOG 1205 is the only randomized study to evaluate the safety and efficacy of reirradiation (reRT) in recurrent glioblastoma (GBM). While this study showed reRT was safe and improves progression-free survival (PFS), an improved approach for reRT is needed. Here, we report on patterns of failure and outcomes of a cohort of patients with recurrent GBM who underwent reRT. We hypothesize that patients at high risk of leptomeningeal spread (LMS) are not good candidates for reRT due to the risk of treatment-related toxicity without clinical benefit.

Methods In this retrospective study, patients with recurrent GBM who underwent reRT at a single institution from 2015-2023 were included. Sociodemographic, treatment, and outcomes data were collected via chart review. Response assessment in neuro-oncology criteria (RANO) was used to evaluate treatment response. PFS and overall survival (OS) were estimated using the Kaplan-Meier method.

Results Thirteen patients with recurrent GBM who underwent reRT were identified. Median age at diagnosis was 58. Six patients (46.2%) had tumors that were MGMT methylated, four (30.8%) were MGMT unmethylated, and three (23.11%) had unknown MGMT status. Eight patients underwent repeat resection after recurrence and prior to reRT. Most patients (n=7) received 35 Gy in 10 fractions with concurrent bevacizumab, while other patients were treated with 25-40 Gy in 5-15 fractions with grade 1 or less acute toxicity. Three patients were treated with tumor-treating fields. Median follow up was five months. Median PFS was three months (95% confidence interval 95% CI, 1-4 months) and median OS was five months (95% CI, 1-8 months) as compared to 7.1 months and 10.1 months, respectively, on RTOG 1205. Five patients developed LMS after reRT, one patient died prior to progression, and the remaining seven patients all developed progression within one centimeter of the recurrent tumor. Of the patients who developed LMS, all had tumors abutting the ventricles and three underwent resection 2-17 months prior to reRT.

Conclusion Patterns of failure suggest a potential treatment selection approach for patients with recurrent GBM, in which patients at high risk of LMS (tumor abutting ventricles with or without recent surgery) should not undergo reRT, while patients at low risk of LMS are good candidates for reRT. Furthermore, reRT could be administered with reduced margins given that all non-LMS recurrences were within 1cm of the original tumor. Additional studies are needed to validate this approach.

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