Investigators, ISUIA

Introduction: The long term effectiveness of preventive intracranial treatment of unruptured aneurysms for hemorrhage and aneurysm-related morbidity and mortality has been hypothesized. No randomized trial has been done. Propensity adjusted comparison within The International Study of Unruptured Intracranial Aneurysms was undertaken to compare long-term effectiveness. Hypothesis: The purpose of this analysis was to compare the long-term outcome in the treatment cohorts (surgery and endovascular) with those of the untreated subgroup. Methods: Patients were subdivided into the initial treatment and untreated cohorts based upon observation or treatment practices in 61 centers from 1991-1998. 1691 patients were in the observational cohort, 471 were in the endovascular cohort and 1917 patients were in the surgical cohort. The cohorts were followed for a median follow-up of 9.2 years. Outcomes were determined prospectively and with central review. The data were grouped together and analyzed to determine treatment decisions. Comparison of outcomes was done using covariate adjustment and using propensity analysis where equivalent probability groups were constructed. Similar main predictors of treatment and outcome were observed. Analysis of hemorrhage, mortality and short-term and long-term morbidity and mortality were assessed. Risk-benefit ratios were also calculated. Results: Significant differences in baseline variables between treatment and observed patients were aneurysm size, symptoms, age, prior SAH or not group, geographical region, family history, hypertension and myocardial infarction history. The results show comparability of groups using the patient propensity-based score subset. Using the propensity score method, the results showed a benefit in prevention of hemorrhage by surgery and endovascular treatment versus observation (p<.01). No difference was found between endovascular versus surgery. However when procedure-related outcomes are included, no significant difference at 1 year, 5 years or 10 years in the combined aneurysm or procedure related endpoint was evident between cohorts. Conclusions: Propensity score matching to achieve comparability resulted in balanced groups. Comparison of long-term results showed that intervention demonstrated a benefit in reducing hemorrhage risk. However, peri-procedural risk negates any short-term benefit for 10 years.