Purpose of review: The purpose of this review is to consider why the International Subarachnoid Aneurysm Trial (ISAT) led to such an uproar, provide a summary of the criticisms of the study and responses from the investigators, and discuss the implications of ISAT.
Recent findings: The ISAT was destined for controversy. It pitted two different treatment modalities directly against each other: one a highly evolved, established means for repairing ruptured intracranial aneurysms and the other a radically different, developing approach. The criticisms of the ISAT fall into several categories. They include study site selection, patient selection and the definition of clinical equipoise, relative expertise of the surgeons and interventionists, and the duration and type of follow-up. While some of the criticisms of ISAT reflect unavoidable statistical, design and temporal constraints and thus are of little impact, others are more consequential and revolve around the need for clinical equipoise, and how that was defined across centers. In addition, the question of surgical expertise needs to be addressed. Finally, long-term outcome data are needed.
Summary: The study was well designed and executed. The published results met the most up-to-date standards for reporting clinical trials. Important questions remain to be answered, including how to define clinical equipoise and the long-term durability of coiling aneurysms.