Don’t use lung CT for heart care, cardio rads advise

The prospect of leveraging lung cancer CT image data to look for other diseases of the chest is an appealing one, especially in this age of prioritizing value over volume. Indeed, a sound case for wide adoption of the practice has been made.

Not so fast, argue three cardiothoracic radiologists in an opinion piece published online Oct. 4 in JACR.

Specifically, it’s best not to report coronary calcium scores—whether quantitative or qualitative—on lung cancer screening CT reports, contend Adam Bernheim, MD, William Auffermann, MD, PhD, and Arthur Stillman, MD, PhD, all of Emory University in Atlanta.

The authors acknowledge that heart disease kills many more people than lung cancer even among heavy smokers.

However, for the overwhelming majority of patients eligible for CMS coverage of low-dose CT for lung cancer screening—those aged 55 to 77 with a smoking history of at least 30 pack-years—“little value will be added that will actually effect any change in management,” the authors write.

That’s so, they maintain, because most of these patients will already be either in the high-risk category, and so should be on statin therapy, or in the intermediate-risk group for which such treatment should be considered.

Pointing to an atherosclerotic cardiovascular disease risk calculator released in 2013 by the American College of Cardiology (ACC) and the American Heart Association (AHA), Bernheim and colleagues say this tool would deem pretty much every screening-eligible smoker as being at high risk for a cardiovascular event.

They underscore that the ACC and AHA already call for statin therapy for these patients, having issued the recommendation in the same joint guidelines that introduced the risk-calculation tool.

“This is the case even if all other clinical variables included in the calculation are normal (normotensive, normal cholesterol levels, no diabetes, etc.),” Bernheim and co-authors write. “Therefore, there is questionable value in demonstrating the absence or presence of coronary calcium on a lung cancer screening CT when the patient will be a high-risk individual regardless of the result.”

In fact, they add, the absence of coronary calcium in this patient population “should not be interpreted as implying that risk is low or that statin therapy should be withheld.”

The authors further note some technical obstacles standing between clinical decision helps and quantitative reporting of calcium scoring in the lung cancer screening CT population.

One such challenge has to do with the fact that, in the absence of electrocardiography gating, the expected error in calcium score calculation on a low-dose chest CT exam “is anticipated to be greatest for those patients with low calcium scores.

“Consequently, a low calcium score on a lung cancer screening study would provide little assurance that the score was truly low enough to reduce the risk below a level where statins should be either considered or recommended according to the [2013 ACC/AHA] guidelines.”

The authors conclude by allowing that, theoretically, it would seem to make sense to assess CMS’s lung-screening eligible patient population—those aged 55 to 77 with a tobacco smoking history of at least 30 pack-years—for coronary artery calcium when they get their annual low-dose CT lung screenings.

However, the “epidemiologic reality that the majority of these patients are at high risk of heart disease suggests that there is limited value in obtaining this information.

“Ultimately, a calcium score would not influence the recommended treatment for the majority of [these] patients if current treatment guidelines are followed,” Bernheim et al. wrote.