EPID-24. TIMING OF STANDARD-OF-CARE CHEMO-RADIATION THERAPY FOLLOWING SURGICAL RESECTION OR STEREOTACTIC BIOPSY

Abstract

Abstract OBJECT The literature examining the optimal timing for initiating post-surgical therapy after glioblastoma surgery is brimming with inconsistencies, with reports of both deleterious effects and benefits in the delay of post-surgical therapy at various time intervals. Moreover, there is currently limited data pertinent to the post-Stupp regimen era. Here, we use the National Cancer Database (NCDB) to explore this matter, with a focus on patients who underwent the standard-of-care (SOC) Stupp regimen. METHODS The study cohort included newly glioblastoma patients from the NCDB, with exclusion of patients age < 40 [as proxy for isocitrate dehydrogenase (IDH) mutated astrocytoma] and stratified for Methyl-guanine-methyl transferase (MGMT) promotor methylation. Timing of initiating SOC was grouped by 0-2, 2-4, 4-6, 6-8, and > 8 weeks from surgery. Biopsy and craniotomy patients were analyzed separately. The Kaplan-Meier method and Cox proportional hazards regression were applied for survival analysis. RESULTS We identified 6511 glioblastoma patients who underwent SOC therapy with available MGMT methylation status. SOC was initiated in 228 (3.5%), 2478 (38.1%), 2954 (45.4%), 646 (9.9%), and 205 (3.2%) patients at 0-2, 2-4, 4-6, 6-8, and >8 weeks after surgery. For craniotomy patients, initiation of SOC at 0-2 weeks was associated with an increased risk of death relative to SOC initiation at 4-6 weeks (HR: 1.19, p = 0.036). These results remain robust after controlling for the extent of resection, tumor size, and tumor location (HR: 1.19, p = 0.044). Such association was not observed in patients who underwent stereotactic biopsy (HR: 1.27, p = 0.148). Patients who received SOC at 6-8 weeks post-craniotomy (HR: 0.96, p = 0.420) or biopsy (HR: 0.93, p = 0.628) did not appear to worsen survival outcomes. CONCLUSION Optimal timing for initiation of SOC differ for craniotomy and needle biopsy patients. Initiating SOC within 2 weeks after craniotomy could lead to worse survival outcomes for GBM patients.