A feasibility study has found that coronary artery calcium scanning has the potential to better target patients who truly need statin therapy, reduce unnecessary statin prescriptions, and improve medication adherence than the current standard of using pooled cohort equations to determine atherosclerotic cardiovascular disease risk.
Dr. Joseph B. Muhlestein
Researchers at the University of Utah, Salt Lake City, and Intermountain Healthcare, a network of 25 hospitals in Utah, reported that the rate of statin usage in patients evaluated with coronary artery calcium (CAC) was 25% lower than in those whose treatment decisions were based on pooled cohort equations (PCE). None of the patients were on statin therapy when they enrolled in the study, published online in JACC: Cardiovascular Imaging.
“This study demonstrates that doing a large outcomes trial is feasible and has a reasonable likelihood of perhaps being a positive trial for the use of CAC,” lead author Joseph B. Muhlestein, MD, said in an interview. Dr. Muhlestein is codirector of cardiovascular research at Intermountain Healthcare and a professor at the University of Utah.
The findings address the 2018 American College of Cardiology/American Heart Association guideline that states PCE is the “single most robust tool for estimating 10-year risk in U.S. adults 40-75 years of age”. However, the guideline also bases statin determination on shared decision-making between the patient and physician, and recommends CAC for patients for whom a decision about statin treatment is uncertain and those at intermediate risk to fine-tune the need for statins.
The results also have spurred a larger randomized trial known as CorCal, which aims to enroll 5,500 patients and compare CAC and PCE, Dr. Muhlestein said. So far 3,000 patients have been enrolled.
Results of CAC vs. PCE
The feasibility study enrolled 601 patients randomized to CAC (302) or PCE (299), 504 of whom were included in the final analysis. In the CAC group, 35.9% went on statin therapy, compared with 47.9% of the PCE patients (P = .005). Participating physicians accepted the study-dictated recommendation to start a statin in 88.1% of patients in the CAC arm versus 75.0% in the PCE arm.
Dr. Muhlestein noted that the feasibility study did not evaluate key outcomes, such as stroke or heart attack, but they will be a key endpoint of the larger randomized trial. “We found in this feasibility study that the recommendations that come from the CAC arm, compared with the PCE arm are significantly different enough that there may be a different outcome,” he said.
“There were cases in which the PCE did not recommend a statin but the patient had a lot of coronary calcium, so we recommended the statin in that patient,” he said. “At the same time, there were also even more patients in which the PCE said they ought to take a statin but they had zero coronary calcium, so we didn’t recommend that they get a statin.”
Compared with PCE-based recommendations, CAC patients were taken off statins in 36% of cases and put on statins in 5.6% of cases. “We think that PCE gives statins to a lot of patients who don’t really need them,” Dr. Muhlestein said.
The feasibility study also found patients were more adherent to therapy if they had CAC than PCE – 63.3% versus 45.6% at a year (P = .03). “Patients and physicians are more likely to be concerned enough to begin preventative therapy when they know that they are not just at risk for the disease, but they actually have the disease; that’s what the CAC score tells them,” Dr. Muhlestein said.
He noted that, while observational evidence has embraced CAC, insurers have been hesitant to cover it. “That is one of the major motivations for us to do this study,” Dr. Muhlestein said. “CAC is not very expensive; it costs less than $100, which is about what it costs to get a lipid panel, but insurance won’t pay for it because we haven’t proved that CAC actually changes outcomes, and that’s a legitimate complaint. But, of course, there’s never been a randomized trial that proves that a PCE changes outcomes either.”
Dr. Neil Stone
The findings validate the 2018 ACC/AHA guideline “and opens a way to broader use for CAC for statin assessment,” said Neil J. Stone, MD, chair of the ACC/AHA 2013 guideline-writing committee and vice chair of the 2018 committee. “The study confirms a large body of information that a deterministic approach, i.e., calcium score, outperforms a probabilistic approach on an individual patient level.” Dr. Stone is the Bonow Professor of Medicine at Northwestern University and medical director of the Vascular Center of the Bluhm Cardiovascular Institute of Northwestern Memorial Hospital, both in Chicago.
“I applaud the investigators for using this as a hypothesis-generating study and planning a larger, more definitive trial,” he said. “This study would encourage regulators and insurance companies to support the use of calcium scores as recommended by the 2018 guideline.”
Intermountain Healthcare is the sole source of funding for the CorCal feasibility study. Dr. Muhlestein and Dr. Stone have no relevant relationships to disclose.