Impact of the Time to Chemoradiation Initiation in Patients with Glioblastoma

Glioblastoma is the most common and most malignant primary brain tumor in adults. Despite advances in modern surgical and adjuvant therapies, glioblastoma remains a challenging disease entity. The standard of care in patients with these tumors includes maximal surgical resection, followed by radiotherapy (RT) with concomitant and adjuvant temozolomide (TMZ). The addition of TMZ to RT has increased both median survival (from 12.1 months to 14.6 months) and the 2year survival rate (from 10% to 26%) in patients with glioblastoma [1]. Although different prognostic groups can be distinguished (e.g., by using the recursive partitioning analysis classification developed by the Radiation Therapy Oncology Group consortium), the overall prognosis of glioblastoma remains poor [2-4]. Studies have demonstrated a negative effect of delayed RT or prolonged treatment duration, mostly in head and neck squamous cell carcinoma and lung cancer, but also in breast and prostate cancer [5-7]. Thus, the presence of a treatmentrelated time factor in aggressively proliferating glioblastoma is likely; however, evidence on the effect of the overall duration of chemoradiotherapy on clinical outcomes has been limited and inconclusive [8-10]. In the context of glioblastoma, the association between delaying CCRT and the outcome is less clear, though some studies have demonstrated an association between a delay in CCRT and poor survival [11-13]. Therefore, this retrospective analysis aimed to investigate the effect of the time to therapy initiation in a contemporary cohort of patients with glioblastoma treated with RT and concomitant adjuvant TMZ in Saudi Arabia.