Effect of a Time Delay for Concomitant Chemoradiation After Surgery for Newly Diagnosed Glioblastoma: A Single-Institution Study with Subgroup Analysis According to the Extent of Tumor Resection

Background: Concomitant chemoradiation (CCRT) after surgical resection has been established as standard care for patients with newly diagnosed glioblastoma (GBM). However, the optimal time interval from surgery to starting CCRT (IST) remains controversial. Methods: The electronic medical records of 160 patients with newly diagnosed GBM treated at our institution between 2009 and 2016 were examined retrospectively. The eligibility criteria were newly diagnosed GBM, pathology confirmed by craniotomy or stereotactic biopsy, and CCRT performed in our institution. Patients who received CCRT within 28 days after surgery were defined as the early group, and those who received CCRT at >28 days after surgery were defined as the delayed group. Results: We included 138 patients who met our eligibility criteria. The median IST was 26 days (range, 10–55 days). In a Kaplan-Meier analysis, overall survival (OS) did not differ between groups (15.5 month for the early group vs. 14.5 months for the delayed group; P = 0.707). In the gross total resection (GTR) subgroup, OS did not differ significantly (20.0 months for the early vs. 21.0 months for the delayed group; P = 0.854). In the non-GTR subgroup, however, the early group had better OS than the delayed group (11.0 months vs. 5.0 months; P = 0.029). Conclusions: Performing CCRT within versus after 28 days after surgery did not result in a statistically significant difference in OS. However, a subgroup analysis showed that delayed CCRT may be associated with worse OS in the non-GTR group.