Purpose: Current guidelines recommend initiating adjuvant chemoradiotherapy within six weeks after glioblastoma surgery, yet delays are common and their impact on survival remains debated. This study evaluates the effect of chemoradiotherapy timing in a monocentric retrospective cohort, with a median radiotherapy (RT) initiation time longer than recommended delays, offering new insight into this underexplored factor.
Methods: Two hundred and fifty-four (254) consecutive patients with newly diagnosed glioblastoma treated by surgical resection followed by chemoradiotherapy between January 2015 and August 2023 were retrospectively included. Patients were classified as 'early' (< 42 days) or 'late' (≥ 42 days) based on the interval from surgery to chemoradiotherapy initiation.
Results: Median time to radiotherapy initiation was 51 days, and 76% of the cohort started chemoradiotherapy ≥ 42 days after surgery. Chemoradiotherapy initiation before versus after 42 days was not associated with overall survival (501 vs. 518 days; 16.4 vs. 17.0 months; HR 1.11, 95% CI 0.80-1.53; p = 0.542) or progression-free survival (HR 1.06, 95% CI 0.77-1.45; p = 0.726), either in univariable or multivariable analyses, including the model incorporating MGMT promoter status. In contrast, maximal extent of resection and MGMT promoter methylation were independently associated with improved survival.
Conclusion: In our cohort of newly diagnosed glioblastoma patients who underwent surgical resection, initiating adjuvant chemoradiotherapy more than six weeks after surgery was not associated with worse overall survival or progression-free survival.
Keywords: Chemoradiotherapy; Glioblastoma; Overall survival; Progression free survival; Radiotherapy delay.
© 2026. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.