ArticlesInternational subarachnoid aneurysm trial (ISAT) of neurosurgical clipping versus endovascular coiling in 2143 patients with ruptured intracranial aneurysms: a randomised comparison of effects on survival, dependency, seizures, rebleeding, subgroups, and aneurysm occlusion
Introduction
The International Subarachnoid Aneurysm Trial (ISAT), a randomised trial comparing neurosurgical clipping with endovascular coiling in patients with ruptured intracranial aneurysms, closed recruitment after an interim analysis showed a benefit of endovascular treatment on the primary outcome: death or dependency at 1 year. Our first report1 of the interim results used the outcome data available at the time of that analysis. These data were incomplete because 1-year follow-up was available for only 1594 of the 2143 patients enrolled. However, the difference between the two treatments was significant: endovascular coiling was associated with an absolute reduction in the risk of death or dependence at 1 year of 6·9% (a relative risk reduction of 22·6%, p<0·001) compared with neurosurgical clipping.1 The 1-year data are now complete and we report here the primary outcome at 1 year for all patients combined and subdivided by the prespecified subgroups.2 We also report results for secondary outcomes: epilepsy, rebleeding from the treated aneurysm, deaths during medium-term follow-up (with survival curves to 7 years), and the findings on follow-up angiography. Patients were eligible for enrolment into ISAT if the responsible neurosurgeon and neuroradiologist were uncertain about the best treatment. If there was insufficient uncertainty, the patient could not be randomised.3
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Patients
The trial protocol and methods, including the randomisation and minimisation criteria, recruiting centres, patient demographics and aneurysm characteristics, have already been published.1, 2 Eligible patients had subarachnoid haemorrhage due to intracranial aneurysm, suitable for either endovascular or neurosurgical treatment. These subgroups were prespecified: World Federation of Neurosurgical Societies (WFNS) grade at randomisation, age groups by decade (<40, 40–49, 50–59, 60–69, ⩾70 years),
Results
Baseline characteristics of the enrolled patients were similar between the treatment groups and have been detailed.1 88% of patients were in good clinical grade (WFNS 1 or 2) at the time of enrolment, 95% of the aneurysms were in the anterior cerebral circulation, and 90% were smaller than 10 mm. The mean follow-up is now 4 years, with 6542 patient years of follow-up available after 1 year.
1073 and 1070 patients were randomised to endovascular coiling or neurosurgical clipping, respectively. Of
Discussion
The final 1-year results presented in this paper reinforce our preliminary findings. Endovascular coiling, compared with neurosurgical clipping, for ruptured intracranial aneurysms that were anatomically suitable for either procedure leads to a significant reduction in the relative risk of death or dependency of 23·9% (12·4–33·9). This equates to an absolute risk reduction of 7·4% (3·6–11·2), which is equivalent to 74 patients avoiding death or dependency at 1 year for every 1000 patients
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