ISAT (Lancet) - 2002

International Subarachnoid Aneurysm Trial (ISAT) of Neurosurgical Clipping versus Endovascular Coiling in 2143 Patients with Ruptured Intracranial Aneurysms: a Randomised Trial | The Lancet

In this paper^[1], the authors enrolled 2,143 patients with ruptured intracranial aneurysms who were treated with either neurosurgical clipping or endovascular coiling. The conclusion advocates endovascular clipping based on the lower rate of death or severe disability at the one-year follow-up.

Study Specifics

Journal: The Lancet
Publication history: Published on October 26, 2002 (Vol 360)
Study type: Multi-center, randomized, controlled clinical trial.
- 42 neurosurgical centers
- Mainly in the United Kingdom and Europe
Interval:
- Pilot phase: 1994
- Full study: 1997
Total patients: 2,143
- Coiling: 1,073 (801 analyzed at 1 year)
- Clipping: 1,070 (793 analyzed at 1 year)
Primary outcome (at 1 year)
- Coiling: 190 (23.7%) were dependent or dead
- Clipping: 243 (30.6%) were dependent or dead
- Relative risk 0·774 (0·658–0·911), p=0·0019
- Relative risk reduction: 22.6% (8.9-34.2)
- Absolute risk reduction: 6.9% (2.5-11.3)
- No significant difference on 1-year fatality rates

Reference Points

"The results show that endovascular intervention with detachable platinum coils in patients with ruptured intracranial aneurysms can improve the chances of independent survival compared with neurosurgical intervention to clip the neck of the aneurysm."
Durability: Critics initially highlighted that surgical clipping offered a more permanent occlusion with less risk of aneurysm recurrence or late rebleeding, requiring longer-term follow-up validation.
- 7-year follow-up published in 2005^[2]: "The early survival advantage was maintained for up to 7 years and was significant (log rank p=0.03). The risk of epilepsy was substantially lower in patients allocated to endovascular treatment, but the risk of late rebleeding was higher."
- 10-year follow-up published in 2015^[3]: "Although rates of increased dependency alone did not differ between groups, the probability of death or dependency was significantly greater in the neurosurgical group than in the endovascular group. Rebleeding was more likely after endovascular coiling than after neurosurgical clipping, but the risk was small and the probability of disability-free survival was significantly greater in the endovascular group than in the neurosurgical group at 10 years."