Large prospective study demonstrates high efficacy and low mortality rates with p64 flow diverter

Diversion-p64 study
Alain Bonafe

The Diversion-p64 study—the largest prospective study using the p64 flow modulation device (phenox) to date—has demonstrated that the device has a high level of efficacy and carries a low rate of mortality and permanent morbidity. This is the conclusion of a report published in the Journal of NeuroInterventional Surgery (JNIS) by Alain Bonafe (Department of Neuroradiology, Hôpital Gui De Chauliac, Montpellier, France) and colleagues.

The authors begin their report by noting that the use of flow diversion to treat intracranial aneurysms has increased in recent years. They add that one of these technologies, the p64 flow modulation device, is approved for the treatment of intracranial aneurysms and dissections in Europe, with a growing body of literature supporting its long-term efficacy.

In an effort to build on this understanding of clinical outcomes associated with the device, the researchers initiated the Diversion-p64 study—a single-arm, international, multicentre, prospective study to assess the safety and efficacy of the device. Between December 2015 and January 2019, patients were enrolled at 26 centres across 10 countries. The authors note in their JNIS report that recruiting sites had to be familiar with the p64 flow diverter, with all participating sites being required to perform five ‘lead-in cases’ with the device, under the supervision of an experienced proctor, prior to study participation.

The primary efficacy endpoint was complete intracranial aneurysm occlusion (Raymond-Roy Occlusion Classification of 1) on follow-up angiography, and the study’s primary safety endpoint was the incidence of major, treatment-related stroke (increase in National Institutes of Health Stroke Scale [NIHSS] score of four points) or neurologic death at three–six months, with a secondary safety endpoint at seven–12 months after treatment. Secondary efficacy endpoints included technical feasibility to deliver and detach the p64 device at the correct location, while secondary safety endpoints included evidence of aneurysm recanalisation or regrowth, as well as thromboembolic, intraprocedural and delayed postprocedural complications.

Bonafe and colleagues report that a total of 420 patients met all eligibility criteria in the study and underwent treatment with the p64 device. The mean age of these patients was 55±12 years, and 362 (86.2%) were female. A total of 445 devices were implanted, resulting in a mean number of 1.06±0.47 devices being implanted per patient. Adjunctive coiling was performed in 14% of cases (n=59).

Relaying the study’s results, the authors state that angiographic follow-up data were available for 357 patients (85%) at the first follow-up—performed at an average of 145±43 days. At this point, complete occlusion and residual neck were reported in 71.7% (n=256) and 4.5% (n=16) of cases, respectively, leading to 76.2% (n=272) of cases demonstrating adequate occlusion. At the second angiographic follow-up—performed at an average of 375±73 days, and available for 343 patients (81.7%)—complete aneurysm occlusion and residual neck were seen in 83.7% (n=287) and 2.3% (n=8) of cases, respectively, resulting in an 86% (n=295) rate of adequate occlusion.

Safety data were available for 413 patients (98.3%) at the first follow-up (mean duration=145±43 days), Bonafe and colleagues continue, and showed a composite morbidity/mortality rate of 2.42% (n=10). In these patients, the major procedure-related stroke rate was 1.9% (n=8), with all of these being due to thromboembolic complications, and the mortality rate was 0.97% (n=4), with two of these deaths relating to a major stroke within the territory of the implanted device. No further episodes of major stroke or death occurred between the first and second follow-up, with data available for 372 patients, the authors add.

After highlighting the main limitations of the Diversion-p64 study—those being its non-randomised nature and the lack of a control arm creating an inherent risk of selection bias—Bonafe and colleagues conclude that the study met its primary efficacy and safety outcomes. “The results of Diversion-p64 demonstrate one of the lowest rates of morbidity/mortality seen in any prospective study on flow diversion,” they add. “It can be concluded that the device has a high efficacy and excellent safety profile that is comparable to other devices.”

Diversion-p64 study
p64 flow modulation device


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