Lung CT Can Detect Coronary Artery Disease, Predict Death

Lung cancer screening with low-dose CT can detect extensive coronary artery calcium (CAC), an independent predictor of all-cause death and cardiovascular events, new research suggested.

“The high prevalence of asymptomatic coronary artery disease (83%) was surprising, as was the prevalence of extensive CAC (30%),” principal investigator Gary Small, MBChB, PhD, a cardiologist at the University of Ottawa Heart Institute, Ottawa, Ontario, Canada, told Medscape Medical News.

“The size of effect was also surprising, as was the persistence of the effect even in the presence of elevated mortality risk from other causes,” he said. “Extensive coronary disease was associated with a twofold increase in risk for death or cardiovascular events over 4 years of follow-up,” even after adjustment for risk for death from cancer and other comorbidities such as chronic obstructive pulmonary disease.

“CAC as reported on chest CT exams is often ignored and not factored into clinical practice,” he noted. “The presence of CAC, however, provides a very real and very personal perspective on an individual’s cardiovascular risk. It is a true example of personalized medicine.”

The study was published online on December 2 in the Canadian Medical Association Journal.

Potential Risk Reduction 

In March 2017, Ontario Health launched a pilot low-dose CT lung cancer screening program for high-risk individuals between the ages of 55 and 74 years, Small explained. As CAC, a marker of coronary artery disease, is seen easily during such a scan, the researchers analyzed the lung CTs to determine the prevalence of coronary artery disease and whether CAC was associated with increased risk.

The team quantified CAC using an estimated Agatston score and identified the composite primary outcome of all-cause death and cardiovascular events using linked electronic medical record data from The Ottawa Hospital up to December 2023. Among the 1486 people who underwent screening (mean age, 66 years; 52% men; 68% current smokers), CAC was detected in 1232 (82.9%). CAC was mild to moderate in 793 participants (53.4%) and extensive in 439 (29.5%). No CAC was detected in 254 (17.1%) participants.

At follow-up, 78 participants (5.2%) experienced the primary composite outcome, including 39 (8.9%) with extensive CAC, 32 (4.0%) with mild to moderate CAC, and seven (2.8%) with no CAC.

Forty-nine deaths occurred, including 16 cardiovascular deaths and 19 cancer deaths, of which 10 were from lung cancer. Cardiovascular events included sudden cardiac death (eight participants), fatal stroke (six participants), and one each from heart failure and peripheral vascular disease.

On multivariable analysis, extensive CAC was associated with the composite primary outcome (adjusted hazard ratio [aHR], 2.13), all-cause mortality (aHR, 2.39), and cardiovascular events (aHR, 2.06).

Extensive CAC remained predictive of cardiovascular events even after adjustment for noncardiovascular death as a competing risk (HR, 2.05).

“Our data highlight to lung cancer screening professionals the prevalence of this silent risk factor and re-emphasize the importance of this finding [ie, CAC] as an opportunity for risk reduction,” Small said.

“In terms of next steps, the journey toward cardiovascular risk reduction begins with a clear report of CAC on the lung cancer screening record,” he noted. “Following this step, professionals involved in the lung cancer screening program might consider a local management pathway to ensure that this opportunity for health improvement is not lost or ignored. Preventive medicine of this type would typically involve primary care.”

Managing Other Findings

Commenting on the study for Medscape Medical News, Anna Bader, MD, assistant professor of radiology and biomedical imaging at the Yale School of Medicine in New Haven, Connecticut, said, “Low-dose CT for lung cancer screening offers valuable insights beyond nodule detection, with CAC being among the most significant incidental findings.”

However, she added, a “robust mechanism” to effectively manage other findings — such as thoracic aortic disease, low bone density, and abnormalities in the thyroid or upper abdominal organs — without overdiagnosis, is needed. A mechanism also is needed to notify cardiologists or primary care providers about severe CAC findings.

Challenges that need to be overcome before such mechanisms can be put in place, she said, “include ensuring standardized CAC reporting, avoiding overburdening healthcare providers, mitigating the risk of excessive downstream testing, and ensuring equitable access to follow-up care for underserved and rural communities.”

Providers involved in lung cancer screening “must be trained to recognize the importance of CAC findings and act upon them,” she added. “Awareness campaigns or continuing medical education modules could address this.”

Multidisciplinary lung cancer screening programs can help with patient education, she noted. “Clear communication about potential findings, including the significance of incidental CAC, should be prioritized and addressed proactively, ideally before the exam, to enhance patient understanding and engagement.”

Matthew Tomey, MD, assistant professor of medicine at the Icahn School of Medicine at Mount Sinai in New York City, also commented on the study for Medscape Medical News.

“As a practicing cardiologist, I find it very helpful to look at my patients’ recent or past CT scans to look for vascular calcification,” he said. “Whether or not a scan is specifically protocolled as a cardiac study, we can often appreciate vascular calcification when it is present. I would encourage every physician involved in helping their patients to prevent heart disease to take advantage of looking at any prior CT scans for evidence of vascular calcification.

“Systems of care to facilitate recognition of patients with incidentally discovered vascular calcification would be welcome and, on a large scale, could help prevent cardiovascular events,” he noted. “Such a system might involve facilitating referral to a prevention specialist. It could involve evidence-based guidance for referring physicians who ordered scans.”

Like Bader, he noted the importance of patient education, adding that it could be quite powerful. “We should be doing more to empower our patients to understand the findings of their imaging and to give them actionable, evidence-based guidance on how they can promote their own cardiovascular health,” he concluded.

No funding for the study was reported. Small reported receiving a research grant for amyloid research from Pfizer and honoraria from Pfizer and Alnylam (all paid to the institution, outside the submitted work). Bader and Tomey declared no relevant conflicts.

Marilynn Larkin, MA, is an award-winning medical writer and editor whose work has appeared in numerous publications, including Medscape Medical News and its sister publication MDedge, the Lancet (where she was a contributing editor), and Reuters Health.