Two very different sets of clinical evidence have offered new twists on how nonadherence to cardiovascular medicines not only leads to suboptimal outcomes, but also complicates the data from clinical studies.
One study, a subanalysis of a major trial, outlined how taking more than the assigned therapy – that is, nonadherence by taking too much rather than too little – skewed results. The other was a trial demonstrating that early use of an invasive procedure is not a strategy to compensate for nonadherence to guideline-directed medical therapy (GDMT).
“Both studies provide a fresh reminder that nonadherence is a significant problem in cardiology overall, but also in the trial setting when we are trying to interpret study results,” explained Usam Baber, MD, director of interventional cardiology, University of Oklahoma Health, Oklahoma City, coauthor of an editorial accompanying the two published studies.
Baber was the first author of a unifying editorial that addressed the issues raised by each. In an interview, Baber said the studies had unique take-home messages but together highlight important issues of nonadherence.
MASTER DAPT: Too Much Medicine
The subanalysis was performed on data generated by MASTER DAPT, a study evaluating whether a relatively short course of dual-antiplatelet therapy (DAPT) in patients at high risk of bleeding could preserve protection against major adverse cardiovascular events (MACE) while reducing risk of adverse events. The problem was that nonadherence muddied the primary message.
In MASTER DAPT, 1 month of DAPT was compared with a standard therapy of at least 2 additional months of DAPT following revascularization and placement of a biodegradable polymer stent. Enrollment in the study was restricted to those with a high risk of bleeding, the report of the primary results showed.
The major message of MASTER DAPT was that the abbreviated course of DAPT was noninferior for preventing MACE but resulted in lower rates of clinically relevant bleeding in those patients without an indication for oral anticoagulation (OAC). In the subgroup with an indication for OAC, there was no bleeding benefit.
However, when the results were reexamined in the context of adherence, the benefit of the shorter course was found to be underestimated. Relative to 9.4% in the standard-therapy arm, the nonadherence rate in the experimental arm was 20.2%, most of whom did not stop therapy at 1 month. They instead remained on the antiplatelet therapy, failing to adhere to the study protocol.
This form of nonadherence, taking more DAPT than assigned, was particularly common in the group with an indication for oral anticoagulation (OAC). In this group, nearly 25% assigned to an abbreviated course remained on DAPT for more than 6 months.
In the intention-to-treat analysis, there was no difference between abbreviated and standard DAPT for MACE whether or not patients had an indication for OAC. In other words, the new analysis showed a reduced risk of bleeding among all patients, whether taking OAC or not after controlling for nonadherence.
In addition, this MASTER DAPT analysis found that a high proportion of patients taking OAC did not discontinue their single-antiplatelet therapy (SAPT) after 6 months as specified.
When correcting for this failure to adhere to the MASTER DAPT protocol in a patient population at high bleeding risk, the new analysis “suggests for the first time that discontinuation of SAPT at 6 months after percutaneous intervention is associated with less bleeding without an increase in ischemic events,” Marco Valgimigli, MD, PhD, director of clinical research, Inselspital University Hospital, Bern, Switzerland, reported in the Journal of the American College of Cardiology.
The findings “reinforce the importance of accounting and correcting for nonadherence” in order to reduce bias in the assessment of treatment effects, according to Valgimigli, principal investigator of MASTER DAPT and this substudy.
“The first interesting message from this study is that clinicians are reluctant to stop SAPT in these patients even in the setting of a randomized controlled trial,” Valgimigli said in an interview.
In addition, this substudy, which was prespecified in the MASTER DAPT protocol and employed “a very sophisticated methodology” to control for the effect of adherence, extends the value of a conservative approach to those who are candidates for OAC.
“The main clinical message is that SAPT needs to be discontinued after 6 months in OAC patients, and clinicians need to stop being reluctant to do so,” Valgimigli said. The data show “prolongation of SAPT increases bleeding risk without decreasing ischemic risk.”
In evaluating trial relevance, regulators prefer ITT analyses, but Baber pointed out that these can obscure the evidence of risk or benefit of a per-protocol analysis when patients take their medicine as prescribed.
“The technical message is that, when we are trying to apply results of a clinical trial to daily practice, we must understand nonadherence,” Baber said.
Baber pointed out that the lack of adherence in the case of MASTER DAPT appears to relate more to clinicians managing the patients than to the patients themselves, but it still speaks to the importance of understanding the effects of treatment in the context of the medicine rather than adherence to the medicine.
ISCHEMIA: Reconsidering Adherence
In the ISCHEMIA trial, the goal was to evaluate whether an early invasive intervention might compensate to at least some degree for the persistent problem of nonadherence.
“If you are managing a patient that you know is at high risk of noncompliance, many clinicians are tempted to perform early revascularization. This was my bias. The thinking is that by offering an invasive therapy we are at least doing something to control their disease,” John A. Spertus, MD, clinical director of outcomes research, St. Luke’s Mid America Heart Institute, Kansas City, Mo., explained in an interview.
The study did not support the hypothesis. Patients with chronic coronary disease were randomized to a strategy of angiography and, if indicated, revascularization, or to receive GDMT alone. The health status was followed with the Seattle Angina Questionnaire (SAQ-7).
At 12 months, patients who were adherent to GDMT had better SAQ-7 scores than those who were nonadherent, regardless of the arm to which they were randomized. Conversely, there was no difference in SAQ-7 scores between the two groups when the nonadherent subgroups in each arm were compared.
“I think these data suggest that an interventional therapy does not absolve clinicians from the responsibility of educating patients about the importance of adhering to GDMT,” Spertus said.
In ISCHEMIA, 4,480 patients were randomized. At baseline assessment 27.8% were nonadherent to GDMT. The baselines SAQ-7 scores were worse in these patients relative to those who were adherent. At 12 months, nonadherence still correlated with worse SAQ-7 scores.
“These data dispel the belief that we might be benefiting nonadherent patients by moving more quickly to invasive procedures,” Spertus said.
In cardiovascular disease, particularly heart failure, adherence to GDMT has been associated numerous times with improved quality of life, according to Baber. However, he said, the ability of invasive procedures to modify the adverse impact of poor adherence to GDMT has not been well studied. This ISCHEMIA subanalysis only reinforces the message that GDMT adherence is a meaningful predictor of improved quality of life.
However, urging clinicians to work with patients to improve adherence is not a novel idea, according to Baber. The unmet need is effective and reliable strategies.
“There are so many different reasons that patients are nonadherent, so there are limited gains by focusing on just one of the issues,” Baber said. “I think the answer is a patient-centric approach in which clinicians deal with the specific issues facing the patient in front of them. I think there are data go suggest this yields better results.”
These two very different studies also show that poor adherence is an insidious issue. While the MASTER DAPT data reveal how nonadherence confuse trial data, the ISCHEMIA trial shows that some assumptions about circumventing the effects of nonadherence might not be accurate.
According to Baber, effective strategies to reduce nonadherence are available, but the problem deserves to be addressed more proactively in clinical trials and in patient care.
Baber reported financial relationships with AstraZeneca and Amgen. Spertus has financial relationships with Abbott, Bayer, Bristol-Myers Squibb, Corvia, Janssen, Merck, Novartis, Pfizer and Terumo. Valgimigli has financial relationships with more than 15 pharmaceutical companies, including Terumo, which provided funding for the MASTER DAPT trial.
This article originally appeared on MDedge.com, part of the Medscape Professional Network.
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