Results of the 30-day ABSORB IV, 3-year ABSORB III and 4-year ABSORB II Late Breaking Trials: TCT 2017
Reported from the TCT 2017 Scientific Sessions in Denver, United States
After the presentation of the data coming from 30-day ABSORB IV, 3-year ABSORB III and 4-year ABSORB II, the interventional cardiology community is even more divided into those in favor or not of Bioresorbable Scaffold (BRS) technology. Many interesting points of discussion arise from these data.
When looking at the 30-day results of the ABSORB IV trial, use of a standardized PSP technique seems to have played a role in reaching the primary endpoint of no-inferiority of the ABSORB vs. Xience arm. However, many other findings are difficult to explain. Rate of scaffold thrombosis and TLR indeed seem still higher in the ABSORB than in Xience arm and only restricting the analysis to those patients with ABSORB-III like characteristics, some role of optimal implantation technique can be seen in reducing scaffold thrombosis (from 1.1% of the ABSORB III to 0.4% in the ABSORB IV at 30-days).
However, despite the optimal implantation technique, a lower final MLD was present in the ABSORB vs. Xience arm; for this reason, it should be determined if implantation techniques should be further improved (e.g. mandatory post-dilatation and use of intravascular imaging in all the patients) or if it is time to think about some improvements in the mechanical properties of the bioresorbable platform, making it comparable to a metallic platform.
In the 3-year data of ABSORB III, a trend towards a higher rate of TLF in the ABSORB arm as compared to the Xience arm (13.4% vs. 10.4%) was shown, with a significantly higher rate of device thrombosis (2.3% vs. 0.7%). Although these results were not surprising given the previous 2-year data, it is interesting to see that this scaffold thrombosis rate is consistent with that of the 3-year ABSORB II data. As the optimal implantation technique was still evolving during both ABSORB II or ABSORB III initiation and enrollment, it may represent a common pattern explain this consistency in scaffold thrombosis rate between the two studies.
4-year ABSORB II data showed a higher rate of target lesion failure (11.1% vs. 5.6%) in the ABSORB vs. Xience arm. However, this finding should be considered hereditary from the 3-year follow-up; by looking at the landmark analysis from 3 to 4-years, it seems that not many events were present in any of the two groups with in particular a 0% rate of stent/scaffold thrombosis. Although this does not represent the beginning of a clinical benefit, it may be interpreted at least as the end of the increasing risk of events seen so far with ABSORB as compared to Xience.
As benefits of BVS would lie not in the short term, but rather beyond 3 years when, theoretically, the scaffold is gone, the 4-year data of ABSORB II may help us to understand in which direction we should go. ABSORB III and IV will be pooled together to analyze a final primary endpoint of TLR landmark between 3 and 7-10 years. We therefore still need to wait many years before understanding if a clinical benefit - beyond its bioresorption - can come from BRS technology.