Zilver PTX Drug-Eluting Stent Trial Shows Superior 3-Year TLR Rates in Femoropopliteal Disease Treatment

August 13, 2012—Cook Medical (Bloomington, IN) announced new 3-year data from the Zilver PTX Randomized Controlled Trial of Paclitaxel-Eluting Stents for Femoropopliteal Disease. Gary M. Ansel, MD, a Principal Investigator of the Zilver PTX study, presented the findings in July at the Japanese Association of Cardiovascular Intervention and Therapeutics meeting in Niigata, Japan.

In the 479-patient trial, Cook Medical’s Zilver PTX paclitaxel-eluting peripheral vascular stent demonstrated 83% freedom from target lesion revascularization at 36 months in the PTX group, compared to 70.2% for patients treated with optimal percutaneous transluminal angioplasty and bare metal stents (BMS).

The Zilver PTX device received approval from the Japanese Pharmaceuticals and Medical Devices Agency on January 24 and will be available in Japan once enrollment in a 900-patient postmarket registry is complete; this registry is said to be rapidly enrolling. The device is available in more than 45 countries, though it is currently being reviewed by the US Food and Drug Administration and is not available for sale in the United States.

Putting the Zilver PTX trial and its current data into context, Dr. Ansel explained in comments to Endovascular Today that it is the largest randomized, controlled, core lab-analysed trial evaluating treatment in the femoropopliteal region to date. Past attempts at using polymer-based drug-eluting stents (DES) in this region did not show any significant benefit, but the Zilver PTX DES, a non–polymer-based device, has demonstrated early and sustained 3-year clinical benefits with a reduced need for repeat procedures, continued Dr. Ansel. The Zilver PTX trial population will be followed for 5 years, continuing to evaluate longer-term effectiveness.

“Though we all thought stents would be a continuous irritant to the artery and lead to ever-decreasing clinical patency, the 3-year TLR (retreatment) results are very similar to the 2-year results,” he said. “Clinically, the need for repeat procedures has flattened out. This appears to be a durable treatment in the clinically evaluated population.”

In placing the Zilver PTX trial in the landscape of peripheral stenting studies, Dr. Ansel discussed the favorable results with DES, but pointed to difficulties in comparing results from separately conducted trials and registries, which have different inclusion criteria, patient populations, and evaluative means. 

“Comparing this randomized trial to bare metal stent (BMS) registries and trials is fraught with problems, since the patient populations can be significantly different,” he cautioned. “For example, the RESILIENT population appeared to have fewer total occlusions, which can improve patency [results]. The recently published 3-year RESILIENT trial demonstrated an improved freedom from TLR rate of 75.5%. This was improved compared to the approximately 70% rate of the optimal-PTA-plus-provisional-stent group (which was similar to the control in the Zilver PTX trial). The Zilver PTX 3-year freedom of TLR of 83% is, in fact, numerically larger than the BMS population’s RESILIENT benefit compared to control.”

Although currently only observed in the 12-month Zilver PTX population, Dr. Ansel points out that the more focal pattern of restenosis seen with this device is important to note. If the pattern continues to be observed over the longer term, he believes it will drive future DES usage. “More focal restenosis increases flow rates to the lower extremity, and any restenosis that does, on occasion, occur, might be more simply—and hopefully cost effectively—addressed.”

“As a cardiologist I am as excited as I was just before coronary DES was released,” he said. “Though we may find certain patient subsets where BMS may be appropriate, DES appears positioned to become the gold standard for femoral and proximal popliteal treatment. With the relatively short-term (60-day) study requirement for clopidogrel, the downside appears to be low.”