Conditional Survival after a Diagnosis of Malignant Brain Tumour in Canada: 2000–2008

Abstract

Background: “Conditional survival probability” is defined as the probability that a patient will survive an additional time, given that the patient has already survived a defined period of time after diagnosis. Such estimates might be more relevant for clinicians and patients during post-diagnosis care, because survival probability projections are based on the patient’s survival to date. Here, we provides the first population-based estimates of conditional survival probabilities by histology for brain cancer in Canada. Methods: Canadian Cancer Registry data were accessed for patients diagnosed with primary brain cancers during 2000–2008. Kaplan–Meier survival probabilities were estimated by histology. Conditional survival probabilities at 6 months (short-term, denoted SCS) and 2 years (long-term, denoted LCS) were derived from the Kaplan–Meier survival estimates for a range of time periods. Results: Among the 20,875 patients who met the study criteria, SCS increased by a margin of 16–18 percentage points from 6-month survivors to 2-year survivors for the three most aggressive brain cancers. The LCS for 2-year survivors was 66% or greater for all tumour groups except glioblastoma. The LCS for 4-year survivors was 62% or greater for all histologies. For glioblastoma and diffuse astrocytoma, the LCS increased each year after diagnosis. For all other histologies, the LCS first increased and then plateaued from 2 years after diagnosis. The LCS and SCS both worsened with increasing older age at diagnosis. Summary: We report histologically specific conditional survival probabilities that can have value for clinicians practicing in Canada as they plan the course of follow-up for individual patients with brain cancer.