Too soon to abandon aspirin
First came STOPDAPT-2
Dr. Watanabe and colleagues designed STOPDAPT-2 ACS as a follow-up to their prior STOPDAPT-2 trial, which randomly assigned slightly more than 3000 patients at 90 Japanese centers to the identical two treatment options: 1 month of DAPT followed by 11 months of clopidogrel monotherapy or 12 months of DAPT, except the trial enrolled all types of patients undergoing PCI. This meant that a minority, 38%, had a recent ACS event, while the remaining patients had chronic coronary artery disease. As in STOPDAPT-2 ACS, all patients in STOPDAPT-2 had received a CCEE stent.
STOPDAPT-2 also used the same primary endpoint to tally net clinical benefit as STOPDAPT-2 ACS: cardiovascular death, MI, stroke of any type, definite stent thrombosis, or TIMI major or minor bleeding classification.
In STOPDAPT-2, using the mixed population with both recent ACS and chronic coronary disease, the regimen of 1 month of DAPT followed by 11 months of clopidogrel monotherapy was both noninferior to and superior to 12 months of DAPT, reducing the net adverse-event tally by 36% relative to 12-month DAPT and by an absolute reduction of 1.34%, as reported in 2019.
Despite this superiority, the results from STOPDAPT-2 had little impact on global practice, commented Kurt Huber, MD, professor and director of the cardiology ICU at the Medical University of Vienna.
“STOP-DAPT-2 did not give us a clear message with respect to reducing antiplatelet treatment after 1 month. I thought that for ACS patients 1 month might be too short,” Dr. Huber said during a press briefing.
Focusing on post-ACS
To directly address this issue, the investigators launched STOPDAPT-2 ACS, which used the same design as the preceding study but only enrolled patients soon after an ACS event. The trial included for its main analysis 3,008 newly enrolled patients with recent ACS, and 1,161 patients who had a recent ACS event and had been randomly assigned in STOPDAPT-2, creating a total study cohort for the new analysis of 4136 patients treated and followed for the study’s full 12 months.
The patients averaged 67 years old, 79% were men, and 30% had diabetes. About 56% had a recent ST-elevation MI, about 20% a recent non–ST-elevation MI, and the remaining 24% had unstable angina. For their unspecified P2Y12 inhibition, roughly half the patients received clopidogrel and the rest received prasugrel. Adherence to the two assigned treatment regimens was very good, with a very small number of patients not adhering to their assigned protocol.
The composite adverse event incidence over 12 months was 3.2% among those who received 1-month DAPT and 2.83% in those on DAPT for 12 months, a difference that failed to achieve the prespecified definition of noninferiority for 1-month DAPT, reported Dr. Watanabe, an interventional cardiologist at Kyoto University.
The ischemic event composite was 50% lower among those on 12-month DAPT, compared with 1 month of DAPT, a difference that just missed significance. The rate of MI was 91% higher with 1-month DAPT, compared with 12 months, a significant difference.
One-month DAPT also significantly reduced the primary measure of bleeding events – the combination of TIMI major and minor bleeds – by a significant 54%, compared with 12-month DAPT. A second metric of clinically meaningful bleeds, those that meet either the type 3 or 5 definition of the Bleeding Academic Research Consortium, were reduced by a significant 59% by 1-month DAPT, compared with 12 months of DAPT.
The new findings from STOPDAPT-2 ACS contrasted with those from MASTER DAPT, but in an explicable way that related to different patient types, different P2Y12 inhibitors, different treatment durations, and different stents.
“We’ve seen in MASTER DAPT that if you use the right stent and use ticagrelor for monotherapy there may be some ability to shorten DAPT, but we still do not know what would happen in patients with very high ischemic risk,” concluded Dr. Huber.
“A reduction in DAPT duration might work in patients without high bleeding risk, but I would exclude patients with very high ischemic risk,” he added. “I also can’t tell you whether 1 month or 3 months is the right approach, and I think clopidogrel is not the right drug to use for monotherapy after ACS.”
STOPDAPT-2 and STOPDAPT-2 ACS were both sponsored by Abbott Vascular, which markets the CCEE (Xience) stents used in both studies. Dr. Watanabe has received lecture fees from Abbott and from Daiichi-Sankyo. Dr. Byrne has received research funding from Abbott Vascular as well as from Biosensors, Biotronik, and Boston Scientific. Roffi has received research funding from Biotronik, Boston Scientific, GE Healthcare, Medtronic, and Terumo. Dr. Huber has received lecture fees from AstraZeneca, Bayer, Boehringer Ingelheim, Bristol-Myers Squibb, Daiichi-Sankyo, Eli Lilly, Pfizer, Sanofi-Aventis, and The Medicines Company.
A version of this article first appeared on Medscape.com.