Coronary CTA Fails to Live Up to Its PROMISE in Suspected CAD

SAN DIEGO, CA—In symptomatic patients considered to be at intermediate risk for CAD, using coronary CT angiography (CTA) as a first-line test does not yield better clinical outcomes than various methods of functional testing, according to a study presented March 14, 2015, at the American College of Cardiology/i2 Scientific Session and published simultaneously online in the New England Journal of Medicine. Additionally, an economic analysis of the study found few differences between the strategies.

In the PROMISE trial, investigators led by Pamela S. Douglas, MD, of Duke University School of Medicine (Durham, NC), randomized 10,003 symptomatic patients (87.7% with chest pain) without diagnosed CAD to an initial strategy of coronary CTA or functional testing (exercise ECG, nuclear stress testing, or stress echocardiography) at 193 North American centers from July 27, 2010, through September 19, 2013. Mean patient age was 60.8 years and 52.7% were female. Given the substantial burden of cardiovascular risk factors in the population—patients had a mean of 2.4 risk factors each—the pretest likelihood of obstructive CAD was 53.3%. 

In the coronary CTA arm (n = 4,996), 93.8% underwent CTA as an initial test while 2.9% had a functional test and 3.1% had no test. Nine patients in this arm went directly to catheterization. In the functional testing arm (n = 5,007), the initial testing strategy was a stress test in 93.7%, CTA in 0.9%, and no test in 4.9%. Twenty patients in this arm went directly to catheterization. Optimal medical therapy was encouraged in all patients and both patients and caregivers received educational materials.

At 25 months of follow-up, the rates of the composite primary endpoint (death, MI, hospitalization for unstable angina, or major procedural complication) were low and similar in the coronary CTA vs functional testing arms. Additionally, the rate of the secondary endpoint (composite of the primary endpoint plus invasive cardiac cath showing no obstructive CAD) also was similar.

Overall, 12.2% of patients had at least 1 cardiac cath within 90 days after randomization in the CTA group vs 8.1% in the functional testing group. Catheterization showing no obstructive CAD occurred in 3.4% in the CTA group and 4.3% in the functional testing group (P = .02).

CTA patients had lower median cumulative radiation exposure per patient than the functional testing group (10.0 vs 11.3 mSv), but approximately one-third of those in the functional testing group had no exposure, resulting in higher mean exposure in the CTA group (12.0 vs 10.1 mSv). Importantly, in patients for whom the intended test before randomization was nuclear stress testing, cumulative radiation exposure was lower with CTA (mean 12.0 vs 14.1 mSv; P < .001).

Trial Provides Reassurance

Dr. Douglas and colleagues say the mix of functional tests used in the study provides a “snapshot of current practice” across the enrolling sites and suggested that contemporary care is responsible for the low event rates in the study. 

Despite the lack of differences between groups, Dr. Douglas called coronary CTA “a viable alternative to functional testing” and said the real-world results should inform noninvasive testing choices in clinical care as well as provide guidance to future studies of diagnostic strategies in suspected heart disease.” 

Asked how she will use this information in her own practice, Dr. Douglas said she felt that she could be “incredibly reassuring” with patients about their overall prognosis and could offer the test best suited to the patient. She added that additional studies are needed to tease out which patients are at lowest risk and fall into a “no testing” category.

Similarly, panelist Valentin Fuster, MD, PhD, of Mount Sinai School of Medicine (New York, NY), said after Dr. Douglas’ presentation that the finding of no real differences raises the question of whether it is better in the long term to have knowledge of the condition of a patient’s coronary arteries while also putting the emphasis on the importance of individual clinical decision making. He added that as coronary CTA evolves, the cumulative radiation exposures are decreasing. 

Dr. Douglas said she anticipates the trial results to affect guideline recommendations by elevating the level of evidence for both coronary CTA and functional testing. 

Marginal Cost Difference

Daniel Mark, MD, MPH, of Duke Clinical Research Institute (Durham, NC), and colleagues conducted the economic subanalysis, which was presented during a media briefing immediately following presentation of the main study results. That study showed that there were no significant differences in costs between the 2 arms.

After looking at the average cost of each test and subsequent follow-up testing, the researchers found that the net cost in the first 90 days was $279 higher on average with CTA than with functional testing. By year 2, however, the cost differential was only $30.

According to Dr. Mark, the trend toward higher costs with CTA compared with functional testing was driven by higher rates of revascularization (6.2% vs 3.2%).

He balked at references to PROMISE as a negative trial, saying instead that while coronary CTA “may not be the Holy Grail of cardiology that we had hoped it would be … it’s more liberal use following the PROMISE standards will definitely improve some aspects of care without causing a major new economic Armageddon in the health care system.”