The endovascular treatment of aneurysms is safer than ever before, according to the results of the Matrix and Platinum Science (MAPS) trial.

"This is certainly something that we as treating physicians have believed, but the current results from MAPS emphatically validate this belief and, in fact, show significant improvement compared to previous studies that have been viewed as benchmarks in our field," said Cameron G. McDougall, MD, president of the Society of NeuroInterventional Surgery (SNIS) and chief of the Section of Endovascular Neurosurgery at the Barrow Neurological Institute in Phoenix, Arizona.

The trial compared 2 types of coils, the Matrix², coated with a polymer, and the GDC coil, a bare platinum coil (both from Boston Scientific) and found the Matrix² coil met criteria for noninferiority compared with the standard GDC coil.

"With this single trial, we have demonstrated that the endovascular treatment of intracranial aneurysms is a very safe treatment and that the Matrix coil is at least as good as bare platinum coils," Dr. McDougall reiterated.

The results were presented at the Eighth Annual Meeting of the SNIS. The trial was funded by Stryker, which owns the Boston Scientific Neurovascular Unit.

TAR New Standard for Measuring Success

In addition to proving that coiling is an excellent treatment for both ruptured and unruptured aneurysms, the MAPS trial also established target aneurysm recurrence rate (TAR) as a new standard for measuring the success of aneurysm treatment, Dr. McDougall noted.

"The GDC and Matrix² coils are platinum coils used to pack intracranial aneurysms and are delivered percutaneously through a transcatheter approach via the femoral artery," Dr. McDougall told Medscape Medical News. "This minimally invasive approach to treating aneurysms has many advantages over open surgical methods that require a craniotomy, but the utilization of endovascular coiling has been limited in its application in part because of the problem of recurrence and the need for retreatment in some patients."

Matrix² coils include an additional bioactive polymer wound around the outside of the platinum core, similar to that used in absorbable sutures. "In animal studies, the polymer reduced aneurysm recanalization or recurrence by creating a more stable occlusion of the aneurysm than that seen when uncoated platinum coils were used," he said.

The US Food and Drug Administration concluded that a separate trial of the Matrix² coil is not required to demonstrate efficacy before its release because it is made of a combination of two previously approved implantable devices, Dr. McDougall explained.

"Thus, clinicians were left uncertain as to whether or not this biologically active coil represented an improvement in patient care. Physicians found themselves in the paradoxical position of having the Matrix coil released with the reasonable expectation that the biological effect demonstrated in preclinical trials would translate into better patient outcomes, but without the clinical data to substantiate this expectation," he said. Hence, the MAPS trial.

The trial included 626 patients aged 18 to 80 years with a single, intracranial saccular ruptured or unruptured aneurysm 4 to 20 mm in size, treated with either Matrix² or GDC coils. The coiling treatment was completed during a single procedure.

The study found that the Matrix² coil was not inferior to the GDC coil.

There was a trend showing subjects treated with Matrix had a lower incidence of TAR when compared with subjects treated with GDC. There was no difference in the reintervention rates between Matrix (10.3%) and GDC (11.1%) at 1 year.

The study also showed that subjects who had less aneurysm occlusion had a greater chance of having a reintervention of their target aneurysm. Of 67 target aneurysm reinterventions, 62 (92.5%) were in asymptomatic patients and were based on their follow-up angiogram Raymond scores.

Final Data From MAPS Eagerly Awaited

It will be important to review and analyze all of the data from the MAPS trial once they are reported and published in detail, Robert D. Brown Jr, MD, MPH, the John T. and Lillian Matthews Professor of Neuroscience and Professor of Neurology at the Mayo Clinic, Rochester, Minnesota, commented to Medscape Medical News.

"As suggested in this abstract, the new type of coil, the Matrix², is 'not inferior' to the standard GDC coil, which has been an option for many years," Dr. Brown said.

"Because interventionalists have so much experience with the GDC coils and have refined the use of that technique over the years, the challenge for any new technology will be to achieve the same low risk or even improve on it," he said. "We certainly look forward to having additional safe options for the treatment of both unruptured and ruptured aneurysms."

He noted that, in general, the neuroscience community is trending in favor of coiling rather than clipping of ruptured aneurysms, although there are some that cannot be safely coiled with standard techniques.

"That's the situation in which new techniques, such as stent-assisted coiling, can be very useful," he said. "I applaud the concept of having another potential option for patients with ruptured aneurysms and those with unruptured aneurysms that need to be treated."

Dr. Brown pointed out that, particularly in the case of unruptured aneurysms, aneurysm natural history needs to be carefully compared to intervention risk as decisions are made regarding the need for treatment. In addition, the difference between the natural history and the management risks cannot be clarified for several years. "The follow-up is relatively short in this study," he noted.

Another issue that has been raised by some neurosurgeons is the durability of the coiling procedure, the need for retreatment, and risk for recurrent hemorrhage when that procedure is used for ruptured aneurysms, he said.

"Again, this underlines the importance of carefully comparing the durability of procedures over the course of time. We will get a better understanding of the impact of this study once the data are fully published. It will be important to understand the characteristics of the aneurysms treated and the nature of the clinical and radiologic assessment used in determining outcomes," Dr. Brown said.

The MAPS study was sponsored by Stryker. Dr. McDougall and Dr. Brown have disclosed no relevant financial relationships.

Eighth Annual Meeting of the Society of NeuroInterventional Surgery (SNIS). Presented July 27, 2011.

Fran Lowry • Medscape Medical News © 2011 WebMD, LLC