Sami Al Kasab, MD

Taschner CA, Chapot R, Costalat V, Machi P, Courthéoux P, Barreau X, et al. Second-Generation Hydrogel Coils for the Endovascular Treatment of Intracranial Aneurysms: A Randomized Controlled Trial. Stroke. 2018

Following the results of the ISAT trial (International Subarachnoid Aneurysm Trial), which showed better functional with endovascular treatment compared to surgical clipping, endovascular therapy became the preferred method for treating most intracranial aneurysms. Incomplete aneurysm occlusion or aneurysm recurrence, however, are among the main limitations of the endovascular approach. The use of detachable coils with or without balloon and/or stent is the most common endovascular approach treating intracranial aneurysms. Bare platinum coils are commonly used to treat intracranial aneurysms; however, given the relatively high recurrence rate, efforts have been made to evaluate the efficacy of newer generation detachable coils. Few new generation coils that aim at providing better packing and aneurysm embolization have been evaluated. Platinum coils coated with polyglycolic acid/polylactic acid polymers that provide inflammatory response at the aneurysm neck failed to prove efficacy. The use of platinum coils coated with hydrogel, which expands once in contact with liquids, leading to increased packing density, was studied in a previous trial and proved to be effective with lower rate of major recurrence; however, its use has been limited by technical limitation. In this trial (German-French Randomized Endovascular Aneurysm Trial), the authors evaluate the use of softer, second generation hydrogel coils for the treatment of intracranial aneurysms.

The GREAT trial was an investigator-initiated, pragmatic, post market, multicenter clinical trial. Patients were eligible if they were 18-75 years of age, had untreated ruptured (WFNS grade 0-3) or unruptured aneurysms measuring 4-12 mm in diameter with an endovascular approach using platinum or hydrogel coil compatible anatomy. Randomization occurred immediately before the intervention. Patients were randomized in 1:1 ratio.

In the intervention arm (hydrogel coil arm), the use of platinum coils was permitted, as were assist devices. The use of second generation hydrogel coil had to constitute > 50% of the total coil length deployed. The antiplatelet/anticoagulation regimen was left to the discretion of the interventionist. The primary endpoint was a composite of predefined unfavorable angiographic and clinical events. The composite primary endpoint included major aneurysm recurrence on follow up angiography within 18 months after treatment, any aneurysm retreatment, mRS 3-5, and any death during treatment or follow up. Secondary outcomes included mRS score at 18 months, total coil length deployed, and coil packing density obtained.

From October 2009 to January 2014, total of 513 patients underwent randomization in 15 centers in France and 7 centers in Germany. Mean age was 52.4 years, and 31% were men. 208 (43%) patients were treated for ruptured aneurysms. 243 (50.2%) patients were randomized to the hydrogel coil; of those, 5 were treated with bare platinum alone. 241 (49.8%) were assigned to the bare platinum group; of those, 6 received additional hydrogel coils. Baseline characteristics, aneurysm rupture status, WFNS score, the use of assist device, size, shape and aneurysm location were comparable in both treatment groups. Primary endpoint data were available in 456 patients.

In the hydrogel group, 181 (80%) patients achieved good composite angiographic and clinical outcome versus 164 (71%). Among patients with recently ruptured aneurysms, 28.7% in the hydrogel group versus 37.6% in the control group experienced unfavorable composite primary outcome (95% CI, -4.3-21.6, P=0.19). Among patients with unruptured aneurysms, 13.6% in the hydrogel group versus 21.7% in the control group experienced unfavorable composite primary outcome (95% CI, -1.2-17.3; P=0.089). After adjusting for aneurysm rupture status, the absolute increase in the risk of unfavorable composite primary outcome for the control group was 8.4% (95% CI, 05-16.2; P=0.036); NNT, 12.

In this study, the use of hydrogel coil was associated with lower risk of unfavorable composite primary endpoint of major angiographic recurrence and poor clinical outcome at 18 months after treatment. Two previous trials compared the use of hydrogel coils to platinum coils. The HELPS trial failed to show significant difference for the composite primary endpoint of the trial. The PRET trial didn’t show any benefit of hydrogel coil over bare platinum with respect to unfavorable composite primary endpoint. There are significant differences in the inclusion/exclusion criteria between these trials and the current study that could account for the difference in results.

The authors of the current study noted few limitations of the study. First, the inclusion of aneurysms measuring 4-12 mm limits its generalizability. Additionally, more patients in the hydrogel group than in the control group had missing primary endpoint data.

In conclusion, the GREAT trial suggests that the use of second generation hydrogel coils in endovascular treatment of small and medium size intracranial aneurysms may be associated with a lower rate of aneurysm recurrence, retreatment, morbidity and mortality.