Radt-31. optimal timing of chemoradiation after resection or biopsy of glioblastomas: a nationwide population-based study

Abstract BACKGROUND The optimal time interval of concomitant chemoradiotherapy (CCRT) after surgery for newly diagnosed glioblastoma (GBM) patients remains controversial. This study was aimed to assess whether the interval between surgery and CCRT leads to a survival difference. METHODS Using the Korean National Health Insurance Research Database, 3,586 patients diagnosed with GBM in South Korea from 2008 to 2021 were retrospectively reviewed. The eligibility criteria were GBM-diagnosed patients who underwent surgical resection or biopsy and received CCRT (with temozolomide (TMZ)) within 6 weeks thereafter. Patients were divided into two groups based on interval between surgery and CCRT initiation: early radiotherapy (RT) within 21 days and late RT > 21 days. Patients were separately examined by the type of surgery – biopsy alone or resective surgery. Overall survival (OS) was estimated using the Kaplan-Meier method and log-rank tests. Univariable and Multivariable Cox regression analyses were performed to assess the impact of the covariables on OS. RESULTS The median OS for early RT group was 20.47 months compared to 17.94 months of late RT group (Log rank P value of 0.0002). Early RT was associated with prolonged OS in multivariable analysis adjusting age, sex, length of stay in hospital after surgery, and the procedure type of biopsy or tumor resection. On the contrary, subgroup analysis showed that patients who received early RT after biopsy showed higher OS than the patients who received late RT (15.93 months vs. 11.83 months). CONCLUSION Patients who received CCRT after 21 days of operation showed better OS than those with earlier CCRT initiation. In contrast, in the group patients who received biopsy alone showed better outcomes when started RT within 21 days. This result suggests that optimal timing of initiation of CCRT after surgery for glioblastoma may be different according to the remnant tumors.