Thank you for the opportunity to speak today. I am Dr. Christina Silcox, I have a PhD in Medical Engineering and Medical Physics from MIT, and I am a senior fellow at the National Center for Health Research. Our research center scrutinizes scientific and medical data and provides objective health information to patients, providers and policy makers. Those are the perspectives I bring with me today. We do not accept funding from device companies and therefore I have no conflicts of interest.
Lumbar spinal stenosis is the most common indication for spine surgery in patients older than 65, and its prevalence in the United States is expected to rise 59% by the year 2025. That means that the FDA’s decision about whether or not to approve this device will affect the lives and health of many men and women. The Superion IDE trial shows that the Superion ISS Device is non-inferior to the X-Stop device. But does that mean it should be approved?
We have two major concerns. First, we agree with FDA scientists that the 16.3% spinous fracture rate is likely to have clinical significance, despite the sponsor’s claim that it doesn’t. We base that on the fact that the hypothesized mechanism of action depends on intact spinous processes. The Sponsor’s executive summary itself states that part of the purpose of the Superion IDE was to validate the device’s mechanism of action. We are concerned that the similar successful clinical outcomes for the patients with and without spinous process fractures means that the mechanism of action is not understood. Is it possible that the adjacent soft tissues and musculature is playing more of a role than previously thought? If so, what are the potential long-term effects? 68% of the Superion fractures were unhealed at 24 months, compared to 59% for X-Stop. Is the device placement preventing healing? What are the long-term potential effects if so? This is a device that is being proposed for use in patients as young as 45 years old. It is essential to understand the mechanism of action in order to understand the long-term effects of this permanent implant and to avoid the risks of revision surgery in the future.
Our second concern is the effectiveness data. The committee is being asked whether this product should be approved based on its demonstrated non-inferiority to the X-Stop device. However, the FDA’s advisory committee recommended again approval of the X-Stop device because of its questionable benefits. That Advisory Committee thought the data from the pivotal trial did not demonstrate that the benefits outweighed the risks. The FDA approved the device anyway, and since that time, real world evidence has clearly shown that the X-Stop is even less beneficial than the pivotal study indicated. In the study presented today, successful outcomes were only found in approximately 50% of patients in both arms and more than 25% of Superion patients had to have revision surgery by 36 months.
It is common for studies submitted to the FDA to have more favorable outcomes than surgical devices will have in the real world. That’s because the surgeons are the best that the sponsor can identify and the patients are carefully selected according to a protocol that is unlikely to be followed in the real world. For that reason, we can expect that in the real world, the Superion ISS Device will be even less beneficial than it was in the study by the sponsor. Given that Superion found a correlation between the spinous process fracture risk and the spinous process placement of the device during surgery, this is a particular concern.
I do not know why the FDA ignored the previous Advisory Panel recommendation and approved the X-Stop anyway, but I do know that in 2004 the FDA had lower standards for PMA approval than they have today. The FDA leadership has changed and efforts have been made to be more consistent.
If you consider the higher standards of evidence currently used for this very important indication, and the real world data indicating that the X-Stop device has risks that outweigh its benefits for most patients, if you were considering the X-Stop today it is very likely that this Advisory Committee would again recommend AGAINST approval and this time the FDA would agree.
HOWEVER, the task today is to focus on the Superion ISS and whether its benefits outweigh the risks of surgery without the device. It does not make sense to approve another device meant for the same population that does not demonstrate superiority even when the best surgeons and most appropriate patients are selected for the study. Even more importantly, when the X-Stop was approved 11 years ago, it filled a gap between open surgery and non-surgical treatments that were not very effective. Since then, minimally invasive surgery techniques have become much more common.
In summary:
- The mechanism of action is not clear, making the long-term benefits and risks unknown
- This device is no better than the X-Stop and inferior to surgery without the device – even under the ideal circumstances of a clinical trial. It is likely to be even less beneficial in the real world.
- The X-Stop was approved because it filled a need for patients who could not undergo open surgery. That need has been met because other, more effective minimally invasive surgeries have been developed.
We urge you to vote NO because the data are insufficient to prove that the benefits outweigh the risks or a reasonable assurance of safety or effectiveness.