Three-Year Safety and Efficacy Data Presented From ABSORB China and ABSORB Japan
May 16, 2017—Abbott Vascular announced that results from two randomized clinical studies of the company's fully dissolving Absorb coronary stent showed comparable safety and efficacy to Abbott's Xience drug-eluting stent at 3 years. The data from ABSORB China and ABSORB Japan were presented in a late-breaking session at the 2017 EuroPCR scientific program in Paris, France.
Results from the ABSORB China trial (N = 475) showed that the previously presented 2-year favorable safety and efficacy results for Absorb continued into year 3. There were no new cases of stent thrombosis in either study arm between 2 and 3 years after treatment.
According to the company, the ABSORB China study treated the highest number of appropriately sized vessels among four randomized controlled trials (ABSORB China, ABSORB Japan, ABSORB II and ABSORB III). Current implantation guidelines specify that Absorb should not be implanted in very small vessels (< 2.25 mm by quantitative coronary angiography).
Cumulatively at 3 years, rates of target lesion failure (TLF) were comparable between Absorb and Xience without statistically significant differences. TLF rates were 5.5% for Absorb versus 4.7% for Xience (P = .68). Rates for stent thrombosis were also not statistically significant at 0.9% for Absorb versus 0% for Xience (P = .5). There were a total of two cases of probable or definite stent thrombosis that occurred on days 15 and 622, respectively, with Absorb; postdilatation was not performed in either case, as is now specified in contemporary implantation guidelines.
Clinical outcomes from the ABSORB Japan trial (N = 400) were comparable between Absorb and Xience arms, with no statistical difference in safety and efficacy at 3 years. Abbott Vascular noted that 14% of vessels treated in the study would be considered too small according to today's standards for implantation of Absorb.
Safety events were similar for Absorb and Xience between year 2 and year 3, indicating that the risk of late adverse events with Absorb may remain low if early safety events can be avoided with current implantation technique. TLF rates in this timeframe were 1.6% for Absorb and 1.6% for Xience (P > .99). One stent thrombosis occurred in the Absorb arm between years 2 and 3 (at day 810); the scaffold was determined to be under expanded, stated the company.
According to Abbott Vascular, because of higher event rates during the study's first 2 years—which were presented at the European Society for Cardiology meeting in August 2016—cumulative 3-year adverse events for Absorb were numerically higher than Xience but not statistically significant. At 3 years, TLF rates were 8.9% for Absorb versus 5.5% for Xience (P = .23), and the rate of probable/definite stent thrombosis was 3.6% for Absorb versus 1.6% for Xience (P = .35).
Finally, the company advised that 30-day results of a more contemporary ongoing study (ABSORB IV) that started after implantation technique evolved are expected in the coming months. A preliminary analysis of pooled rates (combined for both Absorb and Xience because the study is not yet unblinded) showed stent thrombosis rates that were less than half of that observed in the United States pivotal trial. Stent thrombosis rates in ABSORB IV were 0.4% at 30 days (n = 2397) and 0.5% at 1 year (n = 1415), compared to 0.9% at 30 days and 1.1% at 1 year in the pivotal ABSORB III study.