Conditional survival in glioblastoma: The evolution of prognostic factors over time

Conditional survival provides insights into the evolution of prognosis over time and reveals changing associations of prognostic factors during disease progression. Data on the temporal evolution of prognostic factors in glioblastoma remain scarce. We analyzed 315 patients with IDH-wildtype glioblastoma from a prospectively collected registry (01/2008-06/2017). Our primary outcome was 12-month conditional survival (CS), defined as the probability of surviving the next 12 months given survival for "s" months. This analysis was conducted at five landmarks (s = 0, 6, 12, 18, 24) for baseline prognostic factors, including tumor volume compartments. 12-month conditional survival estimates at s = 0, 6, 12, 18, and 24 months from diagnosis were 0.51 (95% CI 0.45-0.56), 0.46 (95% CI 0.39-0.52), 0.41 (95% CI 0.33-0.49), 0.43 (95% CI 0.33-0.52), and 0.56 (95% CI 0.42-0.67), respectively. At diagnosis (s = 0), 12-month survival estimates varied significantly with age >60 at diagnosis, preoperative tumor rim volume >20 cm³, absence of O⁶-methylguanine-DNA methyltransferase (MGMT) promoter methylation, postoperative KPS ≥70, residual postoperative tumor >1 cm³, or biopsy only. Residual tumor volume mainly influences survival in the initial months following surgery, while MGMT promoter methylation and age remain significant predictors beyond this period. These findings may refine stratification strategies in recurrent glioblastoma trials.