COBEST Preliminary 18-Month Data Presented at VIVA

October 22, 2009—The preliminary 18-month results for the COBEST (Covered Versus Balloon Expandable Stent Trial) study were presented by principal investigator Patrice Mwipatayi, FCS (SA), MMed, FRACS, at the Vascular Interventional Advances meeting in Las Vegas, Nevada. According to Prof. Mwipatayi, the COBEST data show that in patients with aortoiliac occlusive disease, there is a statistically significant difference in restenosis and freedom from occlusion rates when using the Advanta V12 polytetrafluoroethylene-covered stent (Atrium Medical Corporation, Hudson, NH) versus a bare-metal stent (BMS) for treatment.

The COBEST study is a prospective, multicenter, randomized, controlled trial comparing the V12 covered stent to BMS in patients with iliac occlusive disease. The primary objective of the study is to compare the V12 covered stent to BMS in binary restenosis rate (< 50% stenosis on Duplex ultrasound/angiogram) and freedom from stent occlusion at 1, 6, 12, and 18 months. The secondary objective is to compare ankle-brachial pressure index changes over time and to determine if there is any difference in amputation rates between the two groups. Investigators will also compare outcomes between the two groups in relation to TASC B, C, and D lesions.

The study enrolled 123 patients (167 limbs). At 12 months, there were 81 limbs in the V12 group and 79 limbs in the BMS group. The results showed that 94.7% of patients in the V12 group had < 50% binary restenosis (Duplex scan) compared to 80.8% in the BMS group (P < .05). The data also included that 96.2% of patients in the V12 group had clinical improvement compared to 83.3% in the BMS group (P < .05).

At 18 months, there were 69 limbs in the V12 group and 63 limbs in the BMS group. The results showed that 95.4% of patients in the V12 group had < 50% binary restenosis (Duplex scan) compared to 82.2% in the BMS group (P < .05). The data also included that 94.2% of patients in the V12 group had clinical improvement compared to 76.7% in the BMS group (P < .05).

The amputation rate was 1.2% in the V12 group and 3.5% in the BMS group, and the complication rate was 4.8% in V12 group and 10.7% in the BMS group; no deaths were reported. There were fewer patients with TASC D lesions in the BMS group (7%) than the V12 group (16.1%), but the TASC C lesions were equally distributed in both groups. At 18 months, there was a 2.4% and 4.7% loss to follow-up in the V12 and BMS groups, respectively.

The investigators concluded that there was a significant difference between the V12 stent and BMS for TASC C and D lesions, and the V12 and BMS groups were similar in patency rates for TASC B lesions. They also noted that in the V12 group, if restenosis occurred, it was predominantly located at the ends of the stent or outside the stent, whereas restenosis in the BMS group was predominantly located within the stent.

Prof. Mwipatayi said that the collection of 18-month follow-up data, which is approximately 80% completed, will be concluded by January 2010, but that investigators do not think it will change the trial's current results.