The Predicting the Safety and Effectiveness of Inferior Vena Cava Filters (PRESERVE) Trial has begun publishing its data—but there’s so much more to the story than the numbers, as evinced by Sunday’s PRESERVE session.
To understand the study, you have to start at the beginning. Yesterday afternoon, John A. Kaufman, MD, FSIR, opened the session, "The SIR/SVS Preserve Trial Study: Real-World Use and Outcomes of IVC Filters," with an overview of the last 50 years of inferior vena cava (IVC) filters and beyond.
Treating VTE
“Traditional treatment for venous thromboembolism (VTE) was historically anticoagulation (preventing new thrombus), debulking to remove the thrombus, and interrupting the IVC to prevent pulmonary embolism,” said Dr. Kaufman. IVC interruption has been commonly used to prevent pulmonary embolism since the 1970s. But in the early late 1990s and 2000s, with the advent of retrievable filters, IVC filter use skyrocketed. Dr. Kaufman estimated that, at that time, there was a 157% increase in prophylactic placement as well.
There became a culture and habit of placing IVC filters and then forgetting them, said James B. Spies, MD, MPH, FSIR.
“Not as many were coming out as we would have wanted,” Dr. Kaufman said, pointing to a 2013 Florida retrieval rate of 8.5%. “We began to see a lot going in, but not many coming out.”
Both Dr. Spies and Dr. Kaufman noted that there was a paucity of data showing the safety and efficacy of filters in a real-world use context.
Soon, public health concerns such as deployment issues, perforation, migration and facture began to change the public sentiment toward the safety of IVC filters.
Following this shift, filter utilization began to go down, even as VTE diagnoses rose, and those filters placed began trending more toward managing VTE, rather than prophylactic use.
Nearly a decade ago, the U.S. Food and Drug Administration (FDA) approached SIR, the Society for Vascular Surgery and other organizations to discuss their concerns about filter safety, the current use patterns noted in practice, and the low retrieval rates of retrievable filters. According to researchers, the FDA was interested in a collaborative study that would evaluate all commonly used filters—devices that had been cleared for FDA approval but that had not been used in any substantial trials.
The trouble with trials
Though all were agreed on the need for data, the "how" was much murkier. There were concerns that the study may not address all the safety concerns, since filter fraction and migration of filters or filter segments are rare, Dr. Spies said. And other complications, like the frequency of filter penetration or IVC thrombosis, is low. Furthermore, the manufacturers may have hesitated to take part in a study with competitors, especially in a difficult medicolegal environment.
There were also other concerns from all sides, Dr. Spies said. The FDA wanted data on the safety of IVC filters in general, but also specific filter types. Physicians wanted to know whether one filter was safer than others, while manufacturers were concerned that FDA clearance may be at stake as a result of the study.
Selecting the design was particularly difficult, Dr. Spies said. The perfect study would be a randomized clinical trial, the best way to to control bias, he said. But what could they compare the data to?
“You can’t ethically compare IVC to no IVC in this population,” said Matthew S. Johnson, MD, FSIR.
Ultimately, the researchers and partners decided on an open-label prospective cohort study, a common alternative design. According to Dr. Spies, this model would be easier to manage and recruit to, and would reflect real-world practice.
“But one of the cons is that it reflected real-world practice,” Dr. Spies said. “Which is messy.”
Dr. Johnson echoed this view, describing differences in basic terminology or what constitutes deep vein thrombosis (DVT) vs. Staff turnover, the high rate of new products being released and coordinating participating sites also created challenges.
“In the end, this was the best study plan we could develop that was practical and achievable,” Dr. Johnson said.
The data
The initial findings of PRESERVE were recently published as a freely accessible paper, with results to be presented at SIR 2023 on Wednesday as a Featured Abstract. Initial data indicate that both the primary safety and effectiveness goals were met; this success was supported by high technical success rates for implantation and retrieval, few procedural complications, and low rates of minor filter-related complications and events.
Though the data indicate that filters have efficacy, Dr. Johnson says that patients should be regularly reassessed, with filter removal discussed at each follow-up. “When a filter goes in,” he says, “there should always be a discussion about when it’s coming out.”
Next steps
Now that IRs have more data available, there should be a focus on developing a clearer set of guidelines for VTE, said Rodney A. White, MD, a member of the Society for Vascular Surgery (SVS). Guidelines should also address the use of filters for prophylactic cases and be geared toward improving patient outcomes. That involves initiating patient and family education on the importance of follow-up evaluations and removal discussions.
And there is a need for future studies as well, Dr. White said. Questions and tasks still remain, like defining filter penetration and prophylaxis.
These studies may be aided by the PRESERVE model itself, which researchers believe may be a roadmap for future trials and registries. The model established a dedicated filter tracking system, initiated a process improvement project, brought together a multidisciplinary team and initiated a dedicated filter clinic, Dr. White said. “PRESERVE provides an alternative investigative approach which includes all key stakeholders to develop, perform and maximize collaboration and patient care.”
