Atrium Medical Corporation (Atrium) has released the interim results from the COBEST clinical study. This study is to evaluate the use of bare metal stents vs. balloon expandable covered stents for the treatment of aorto-iliac occlusive disease. Prof. Patrice Mwipatayi of Royal Perth Hospital, Australia, presented interim data on the Covered versus Balloon Expandable Stent Trial known as COBEST at the 2009 VIVA (Vascular InterVentional Advances) meeting in Las Vegas.
COBEST is a randomized, multi-center, prospective trial comparing Atrium’s proprietary balloon expandable covered stent technology (Advanta V12 covered stent) to bare metal stents (BMS) commonly prescribed for iliac occlusive vessel disease.
This important clinical study randomized 167 limbs (123 patients) from 12 hospital centers across Australia. Patients were included if they had occlusive disease and lesions categorized as TASC B, C, or D vessel lesions in their iliac blood vessels. In the study, 83 limbs were randomized to the Atrium Advanta V12 covered stent group and 84 limbs were randomized to the bare metal stent group. Patient characteristics were similar in all groups except for a greater percentage of patients with hypertension in the BMS group and a greater number of challenging TASC D lesions were included in the Advanta V12 covered stent group.
The primary objective of COBEST is to compare the outcomes benefits of balloon expandable covered stent technology to standard of care with bare metal stents. This clinical study comparison included binary restenosis (re-narrowing of the vessel within the treated stent region) and freedom from stent occlusion (a complete blockage). Binary restenosis was primarily assessed through Duplex Ultrasound imaging at 6, 12, and 18 months. In cases where a Duplex Ultrasound image was not obtained, stent performance was achieved through flouroscopic examination (angiogram/X-Ray) and or CT scan. Freedom from stent occlusion was assessed at 6,12, and 18 months for each group.
Secondary objectives included comparing amputation rates, non-invasive tests including ankle brachial index pressures (ABIs), and symptomatic patient outcomes based on the type of lesion classification (TASC B, C, and D lesions), target vessel revascularization, as well as patient relief at each time interval out to 18 months.
The interim data represented 160 limbs with full 12-month follow-up and 132 limbs that have reached the 18-month time frame.
The Advanta V12 covered stent group had significantly less binary restenosis than the BMS group (p < 0.0175) and greater freedom from stent occlusion compared to BMS (p<0.0173). At 18 months, 95.4% of the Advanta V12 covered stent group were free of binary restenosis as compared with 82.2% for the bare metal stent group. Of the covered stent patients, 94.2% showed a clinical improvement at 18 months compared with 76.7% in the BMS group (p<0.008). The covered stent group also experienced a lower amputation rate (1.2%) versus the bare metal stent group (3.6%) and a lower complication rate of 4.8% versus 10.7%. No deaths were reported in the study.
Analysis of the lesion classification showed superiority of the Advanta V12 covered stent in Type C and D lesions over BMS. While no significant difference was seen in the overall patency rate of the randomized clinical trial with patients with Type B lesions, the interim results of the COBEST trial demonstrated that there is a significant benefit with using Atrium’s Advanta V12 covered stent in Type C & D lesions with regards to binary restenosis, freedom from occlusion, and clinical improvement. Bare metal stents in this clinical study experienced a 5-fold increase in target lesion revascularization (TLR).
The Advanta V12 covered stent is an low profile, premounted covered stent made of a radial expandable stainless steel stent that is completely encapsulated with a patented microporous layer of expanded PTFE film. This novel device is approved outside of the United States for the treatment of occlusive and aneurismal vascular conditions involving the iliac and renal arteries. The Advanta V12 covered stent is not available in the US.