Ability to detect CAD confirmed for PET with novel radiotracer
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Key takeaways:
- PET with the radiotracer 18F flurpiridaz had better sensitivity and similar specificity vs. SPECT in patients with suspected CAD.
- Among patients in whom performance was best were women and those with obesity.
Confirming a previous report, PET with a novel radiotracer had good sensitivity and specificity for CAD detection and outperformed single-photon emission CT myocardial perfusion imaging.
As Healio previously reported, in the phase 3 AURORA trial presented at the Annual Scientific Session and Exhibition of the American Society of Nuclear Cardiology in 2022, the PET system, which includes the radiotracer 18F flurpiridaz (GE Healthcare/Lantheus Medical Imaging), exceeded the performance goal of 60% sensitivity and specificity, meaning the lower bound of the 95% CI needed to be more than 60%. Updated data from AURORA were published in the Journal of the American College of Cardiology.
Image: Adobe Stock
The study included 578 patients (mean age, 64 years; 32.5% women; 52.3% with BMI 30 kg/m2; 33.6% with diabetes) with suspected CAD who had evaluable images after undergoing 1-day rest/stress flurpiridaz PET and 1- or 2-day rest-stress Tc-99m–labeled SPECT before invasive coronary angiography. All images were read by three experts who were masked to clinical and invasive coronary angiography data.
Sensitivity higher, specificity similar
Overall, the sensitivity of flurpiridaz PET was higher than that of SPECT (80.3% vs. 68.7; P = .0003), and the specificity was noninferior (PET, 63.8%; SPECT, 61.7%; P for noninferiority = .0004), Jamshid Maddahi, MD, FACC, FASNC, professor of cardiology and nuclear medicine at UCLA School of Medicine, and colleagues wrote.
The area under the receiver-operating characteristic curves were higher for flurpiridaz PET than for SPECT in the overall cohort (0.8 vs. 0.68; P < .0001), in women (0.84 vs. 0.7; P = .0091) and in patients with obesity (0.79 vs. 0.67; P = .0008), and trended toward being higher in patients with diabetes (0.76 vs. 0.69; P = .0887), according to the researchers.
“The observed noninferiority of flurpiridaz PET specificity vs. SPECT may be related to readers’ bias toward higher SPECT specificity by assigning true defects as artifacts,” Maddahi and colleagues wrote. “This is supported by the observation that the area under the receiver-operating characteristic curve was significantly higher for flurpiridaz PET vs. SPECT in the overall population as well as the subgroup who underwent attenuation-corrected SPECT studies.”
Flurpiridaz PET was also superior to SPECT in perfusion defect size/severity evaluation, image quality, diagnostic certainty and radiation exposure (P < .001 for all), Maddahi and colleagues found.
“The clinical importance of these findings is highlighted by the fact that the majority of patients undergoing stress myocardial perfusion imaging for evaluation of CAD fall in one or more of these clinical subsets [female sex, obesity and diabetes] that are not well assessed by SPECT MPI,” the researchers wrote.
‘Diagnostic and prognostic advantages’
In a related editorial, Jamieson M. Bourque, MD, MHS, medical director of nuclear cardiology at the University of Virginia Health System, wrote that “18F flurpiridaz promises greater availability, with a longer half-life of 110 minutes that supports acquisition from a regional cyclotron. The unit dosing supports use in low-volume centers, such as those starting new PET myocardial perfusion imaging programs, where the high number of referrals necessary to make a high-cost generator financially feasible are not attained. The longer half-life also supports the routine use of exercise stress, with all the associated diagnostic and prognostic advantages.
“Cardiac PET prognostic advantages is positioned to serve as the leading modality for the functional evaluation of suspected and known CAD,” he wrote. “18F flurpiridaz will facilitate this upward progression with beneficial tracer characteristics that will increase access and availability, enable exercise stress, and optimize quantification. AURORA is lighting the way to an exciting new era in cardiac imaging.”
Reference:
Perspective
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Mouaz H. Al-Mallah, MD, MSc, MASNC
We now have a new radiopharmaceutical that is going to be very helpful for expanding cardiac PET and allowing more patients to have access to this important modality. The study confirms our knowledge that PET is superior to SPECT. This has been tested in many studies before, and has been affirmed in the American College of Cardiology/American Heart Association guidelines. In addition, cardiac PET has been shown to have the highest accuracy compared with any other modality; it provides the best balance between sensitivity and specificity.
This agent has some characteristics that allow us to expand our current reach of cardiac PET. Today, cardiac PET is only done when you have a rubidium generator or a cyclotron on-site. Therefore, you need to have a minimum volume of patients to do cardiac PET. With this agent, when it is hopefully FDA-approved, you can order one or more doses and have even a small number of patients undergo cardiac PET perfusion. This will have significant implications for the clinical practices that are not able to offer cardiac PET right now under the current business model. The agent will allow more sites to provide cardiac PET, an important modality for many patients who currently do not have access to it when they need it. There are more than 3,000 PET machines installed in the U.S., but currently only a small minority of them are able to do cardiac PET.
Cardiac PET becoming more widely available will help not only the overall population with suspected CAD, but also especially patients with female sex, obesity and/or diabetes, who currently have challenges when undergoing various imaging modalities. In addition, cardiac PET has a unique advantage in how it can assess myocardial blood flow; this is also endorsed in the guidelines. That will allow us to diagnose more patients with microvascular dysfunction — angina or ischemia without obstructive disease (ANOCA or INOCA); right now, cardiac PET is not accessible by most of those patients.
There are many patients who would benefit from cardiac PET, and increasing its use will hopefully increase appropriate referrals to the cath lab, and decrease inappropriate referrals. More widespread use of cardiac PET would allow us to image more challenging patients, such as those with morbid obesity or those with diabetes and multivessel disease, more accurately, and be more sure of the results for them compared with other modalities.
This study and this agent when available will open the door for cardiac PET to become more mainstream. It would allow us to better serve our patients with suspected or known CAD. It will be very exciting to offer this technology to more patients who need it and who would benefit from it.
Beverly B. and Daniel C. Arnold Distinguished Chair
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