The International Subarachnoid Aneurysm Trial (ISAT) was a prospective, randomised trial comparing surgical clipping of ruptured cerebral aneurysms to endovascular coiling and was published in The Lancet.141 This study demonstrated that for a carefully pre-selected subgroup of patients, cared for in designated study centres, patients with ruptured aneurysms treated with coiling fared better at one year follow up than patients treated with surgical clipping at those designated centres. Unfortunately, we believe that the ISAT study results have been misrepresented in the international media and that very specific data have been inappropriately generalised to all patients with intracranial aneurysms. The reported ISAT data relate that patients with aneurysmal SAH treated with craniotomy and aneurysm clipping at the study centres had a 30-6% incidence of poor outcome at one year follow up. Patients with ruptured aneurysms treated by endovascular coiling at these centres had 237% chance of poor outcome at one year follow up. The absolute risk reduction at one year follow up when comparing coiling versus clipping at the study centres was 69%. The majority of the centres involved in the study were located in Europe (particularly England), Australia, and Canada. Only two patients were entered into the study from a single centre within the United States, where practice patterns and neurovascular subspecialisation, particularly in major academic centres, is very different. The number of procedures performed per neurosurgeon/endovascular specialist participating in the ISAT trial heretofore has not been published and is critical in determining the relative expertise between the different treatment modalities.
More importantly, of 9278 patients with ruptured intracranial aneurysms considered for the ISAT study, only 2143 patients were randomised, with the majority of the remaining 7135 patients undergoing craniotomy for aneurysm clipping. As well, during the short follow-up period of the report, 26% of the patients who underwent coiling suffered a haemorrhage after treatment, compared to 09% of the surgical group. In addition, more than four times more patients treated with aneurysm coiling in the ISAT study required additional treatment for their ruptured aneurysms than did patients treated by microsurgical clipping. The 2143 patients randomised in the ISAT study will need to be closely followed for many years before legitimate conclusions regarding the durability of endovascular coiling and the comparative outcomes of coiling versus clipping can be deduced.
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