ATCT-29INVESTIGATING THE EFFECT OF REIRRADIATION OR SYSTEMIC THERAPY IN PATIENTS WITH GBM AFTER TUMOR PROGRESSION: A SECONDARY ANALYSIS OF THE NRG ONCOLOGY/RTOG 0525

BACKGROUND: There is limited evidence regarding which salvage treatment approach may be of most benefit for glioblastoma patients who progress following standard chemo-radiation treatment. METHODS: This secondary analysis of RTOG 0525 investigated the effect of reirradiation or systemic treatment in patients with tumor progression. Survival time was calculated from date of progression. Survival from first progression was estimated and compared between patients receiving neither radiation or systemic therapy, systemic therapy alone, or any radiation treatment. Patient characteristics were compared between groups and the Cox proportional hazards model was used to compare hazard of death controlling for potential confounders. RESULTS: A total of 637 patients who progressed with recorded information on their non-protocol therapy, excluding those who died less than half a month after progression, were analyzed. 267 patients (42%) received neither radiation or systemic treatment at progression. 88 patients (14%) received some form of radiation treatment. 282 patients (44%) received systemic treatment only. Patients who received no treatment had a median survival (MS) of 4.8 months, lower than radiation treatment (11.3 months), or systemic therapy (10.6 months). However, there was no survival difference between patients who received systemic therapy and those who received radiotherapy (p = 0.3808). Cox models, controlling for potential confounders, demonstrate no difference in hazard of death (1.13, 95% CI 0.8-1.5) between treatment arms. Patients receiving neither therapy had a statistically significant increased hazard of death (2.45, 95% CI: 1.9-3.1). CONCLUSIONS: Salvage treatments after GBM tumor progression were highly variable. Patients who received radiation with or without systemic therapy had a similar MS as those receiving systemic therapy only. Either treatment was statistically significantly better than no treatment. However, this may be the result of poorer functional status of untreated patients. SUPPORT: This project was supported by grants U10CA21661, U10CA180868, U10CA180822 and U10CA37422 from the NCI and Merck.