Is Timing of Adjuvant Radiotherapy in Newly Diagnosed Glioblastoma Important?

Abstract

Background: The effect of timing of adjuvant radiotherapy on survival has not been well defined. In this study, we evaluated the effect of time interval between surgery to radiotherapy initiation on overall survival in glioblastoma patients. Methods: In this retrospective study, 392 histopathologically confirmed glioblastoma patients treated between January 2008 to June 2016 were included. All patients were planned for maximal surgical resection, 3D conformal or intensity modulated radiotherapy with six cycles of concurrent temozolomide followed by six cycles of adjuvant temozolomide. We classified patients into three groups based on time interval between surgery to start of radiotherapy: ≤ 10 days, 11- 20 days and > 20 days. Primary end-point was overall survival. Survival times were estimated by Kaplan-Meier method. Univariate and multivariable regression analysis were performed to determine the prognostic factors of survival outcomes. Findings: The median time interval between surgery and starting radiotherapy was 15 days. The overall median survival in all patients was 14.7 months. The median follow-up was 48.6 months. The median survival was 18.3 months when surgery to starting radiotherapy time interval was ≤ 10 days, 13.2 months when the time interval was 11-20 days and 14.7 months when interval was > 20 days. The hazard ratio for 11-20 days' time interval was 1.95 (95% confidence interval, 1.49 - 2.55; P 20 day's time interval group was 1.71 (95% confidence interval, 1.19-2.44; P = 0.004) when adjusted for known prognostic factors like age, Karnofsky performance status and extent for resection. Interpretation: Our findings suggest that surgery to radiotherapy time interval of more than 10 days had a significant detrimental effect on overall survival in glioblastoma patients. Funding Statement: The authors declare: No funding received. Declaration of Interests: All the authors declare no conflict of interest. Ethics Approval Statement: Approval was obtained from the Institutional Ethics Committee, AHERF (Apollo Hospitals Education and Research Foundation).