Biotronik's BIOFLEX-COF Trial Investigates Influence of Chronic Outward Force on Stent Patency

September 11, 2019—Biotronik announced that 12-month results of the BIOFLEX COF trial have demonstrated that the implantation of stents with low chronic outward force (COF) was associated with less neointimal hyperplasia, resulting in less restenosis.

According to the company, the study’s background is that self-expanding nitinol stents must be oversized by at least a minimal amount to ensure contact with the vessel wall and prevent migration. The deployed stent exerts a continuous force on the vascular wall, termed COF. An animal study has found increased neointimal hyperplasia, inflammation, and injury scores in vessels treated with high-COF stents. However, human data have not been available until now.

The investigator-initiated BIOFLEX-COF randomized controlled trial (RCT) enrolled 83 patients with symptomatic peripheral arterial lesions eligible for endovascular stent implantation. The patients were randomized 1:1 to either a high- or low-COF group. The trial’s primary endpoint is the amount of in-stent restenosis at 1 and 2 years as assessed by contrast-enhanced CTA.

In the trial, patients treated with Biotronik’s low-COF Pulsar stent showed significantly lower restenosis rates than patients treated with the high-COF LifeStent device (BD Interventional). The trial’s principal investigator, Professor Martin Funovics, MD, from the Medical University of Vienna, Austria, presented the full cohort primary endpoint data at CIRSE 2019, the annual conference of the Cardiovascular and Interventional Radiology Society of Europe held September 7–11 in Barcelona, Spain.

The company reported that BIOFLEX-COF is an RCT to investigate differences in clinical outcomes of nitinol stents with high versus low COF in de novo superficial femoral artery occlusive arterial lesions. The mean restenosis rate was 26% for the low-COF Pulsar stent versus 35% for the high-COF LifeStent, as measured on CTA at 1 year (P < .001, t test and Mann-Whitney U test).

Prof. Funovics commented in Biotronik’s announcement, “We initiated the BIOFLEX COF trial to close the gap on how COF impacts the human neointima. These RCT data support our hypothesis that high COF leads to increased neointimal hyperplasia, which causes restenosis and increases the risk of repeat interventions for the patient. Our results suggest that COF impacts clinical outcomes and should, therefore, be an important factor in the choice of the stent.”