Conditional probability of long-term survival in glioblastoma: A population-based analysis

Background: Advances in glioblastoma care have resulted in a larger proportion of patients surviving beyond 2 years after diagnosis. It is not clear how long-term survivors should be counseled with respect to future prognosis, or what factors influence that prognosis. The conditional probability of survival was evaluated from multiple time points in patients with glioblastoma, using Surveillance, Epidemiology, and End Results (SEER) data. Methods: Patients diagnosed with glioblastoma from 1998 to 2008 who were treated with radiation-containing regimens were identified within SEER data. Conditional survival probabilities from multiple survival points were calculated. Cox proportional hazards models were constructed to identify predictors of survival from diagnosis and from 1 and 2 years after diagnosis. Results: A total of 10,022 patients with glioblastoma met study inclusion criteria; median survival was 12.61 months. Conditional probability of surviving an additional 2 years ranged from 19.8% at diagnosis to 65.9% at 5 years after diagnosis. The proportion of patients surviving 12 months from time of diagnosis as well as from 6, 12, and 18 months after diagnosis was significantly higher in patients diagnosed in 2005 through 2008 than those diagnosed in 1998 through 2004. Of demographic and treatment-related factors evaluated, only age was associated with hazard of death at diagnosis and 1 and 3 years after diagnosis (P <.0001 at each time point). Conclusions: Patients surviving past 2 years from diagnosis have a relatively favorable conditional probability of survival into the future compared to newly diagnosed patients. This effect becomes more pronounced with increasing time since diagnosis. These data will assist in the counseling of glioblastoma survivors.