How much can be concluded from the International Subarachnoid Aneurysm Trial (ISAT)?

Recently published data from the International Subarachnoid Aneurysm Trial (ISAT) shows that for patients enrolled in the trial there is a 7.4% reduction in the incidence of death or dependency at 1 year if they undergo coiling, rather than clipping. Furthermore, extrapolation of longer-term follow-up data for patient mortality appears to suggest that this advantage will be maintained in the longer term. Based on a reassessment of the published data, the authors note: (1) the incidence of rebleeding following treatment is approximately three times higher in the coiled group (p<0.001); (2) the need for aneurysm retreatment is likely to be higher in the coiled group; (3) trends in longer-term mortality data are not a reliable basis for predicting future outcomes of the trial; (4) trends in longer-term morbidity data are more reliable and suggest that the advantage of coiling diminishes with time; (5) The absence of up-to-date published rates of aneurysm retreatment and of longer-term rates of death or dependence makes ISAT extremely hard to interpret. It is far from clear that the early advantage of coiling will be maintained in the future and, hence, longer follow-up is required. Treatment of aneurysms is a continually evolving field and there is currently no other major source of information concerning management of aneurysms. For these reasons the authors recommend the instigation of a national aneurysm registry to prospectively collect data.