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Talking Points on The International Subarachnoid Aneurysm Trial (ISAT)

1. The International Subarachnoid Aneurysm Trial (ISAT), a prospective randomized trail of craniotomy for aneurysm clipping versus endovascular coiling for ruptured intracranial aneurysms, was published Saturday, October 26, 2002 in The Lancet.
   
   
2. Most centers in the study were located in Europe (particularly England) and Canada. Only two patients were entered into the study from a single United Stares center. The results from ISAT may not be applicable to the United States, where practice patterns, particularly in reference to the degree of sub-specialization of neurovascular surgeons in major centers, are different.
   
   
3. The study included 2143 randomized patients with ruptured aneurysms. Patients were randomly assigned to be treated by aneurysm clipping or by endovascular coiling for their ruptured aneurysms. One year after randomization, ~24% of the coiled patients had died or were disabled, compared to ~31% of those who were treated with clipping.
   
   
4. The absolute risk reduction at one year for clipping versus coiling was 6.9%, not 22.6% (the relative risk reduction) as has been cited in the media. The figure of 22.6% makes it sound as though there is a dramatic difference in the number of poor outcomes with coiling versus clipping. This is not the case. It should also be noted that it is the absolute risk reduction that is of importance to the patients.
   
   
5. The results of the ISAT study are based on the functional outcomes of aneurysm patients with coiling or clipping after one year. The patients need to be followed for many years before legitimate conclusions can be drawn about which treatment is safer.
   
   
6. Although coiling is a suitable treatment option for some patients, the neurosurgeon must consider all factors to determine whether or not a patient is best treated by clipping or coiling. Nothing in the ISAT study indicates that coiling is the best treatment for most or all aneurysms.
   
   
7. Our interpretation of the ISAT results is as follows: "In a patient with a subarachnoid hemorrhage whose ruptured aneurysm is considered suitable for clipping or coiling, and for whom the neurovascular surgeon and the endovascular surgeon do not know, after considering all factors, which treatment option is better for a specific patient with a ruptured intracranial aneurysm, aneurysm coiling, at the centers involved in the ISAT study, yielded a 6.9% chance of a better functional outcome at one year follow-up compared to similar patients with ruptured aneurysms treated with craniotomy for clipping. Long term follow-up of these patients will be essential to determine if aneurysm clipping or aneurysm coiling is the safer treatment for this subgroup of ruptured aneurysm patients over their lifetimes."
   
   
8. Patients with intracranial aneurysms should be referred to a vascular neurosurgeon to be evaluated for the most appropriate treatment.