Unknown Extracardiac Malignancies Discovered in CT

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Extracardiac Malignancies Discovered in CT

Based on a new study published in the American Journal of Roentgenology, cardiac CT identifies grave extracardiac malignancies in one out of every 150 patients, a discovery that could have severe repercussions on who should be allowed to read and interpret heart CT scans; radiologists, cardiologists, or perhaps both.

In a large scale analysis that involved 15,000 patients distributed across 19 studies, CT scans revealed a rate of about 0.7% of serious extracardiac malignancies, three-fourths of which were all previously unknown, noted the research team.  However researchers reported that the commonness of all cardiac abnormalities, not only cancers, differed widely across the studies.

"Although the prevalence of reported incidental extracardiac finding at cardiac CT was highly variable, a homogeneous prevalence of previously unknown malignancies was reported across the studies," Dr. Nicola Flor and colleagues from Azienda Ospedaliera San Paolo and other clinics in Milan wrote. Extracardiac discoveries at cardiac CT call for specific assessment and coverage, they stated.

The authors also mentioned that Cardiac CT, the original diagnostic tool for patients at low and moderate risk of coronary artery disease, is noticeably different from other cardiac imaging systems such as echocardiography, SPECT myocardial perfusion imaging, and traditional angiography in its ability to detect extracardiac cancers in a wide array of organs and areas.

"Cardiac CT images generally include portions of the lungs, pleura, chest wall, mediastinum, dorsal spine, and upper abdomen. Considering the increasing availability of advanced CT scanners and the number of cardiac CT studies, incidental extracardiac findings are frequently detected in clinical practice. Of these, significant numbers are previously unknown malignancies,” wrote Flor and the research team.

Several studies have observed minor cardiac findings, but the aim of this analysis was to examine the commonness of extracardiac findings in cardiac CT patients in order to develop an estimate of how often they occur.

The research team took to digging and pulling relevant information in the PubMed, Embase, and Cochrane databases for studies reporting minor extracardiac findings on CT. After heavy review that involved both manual and computerized searches, 19 studies including 15,877 patients (67% male) were found to meet the study criteria.

In all, 15,877 patients (10,194 male and 5,683 female) were included in the analysis. In conjunction with the subjects' clinical status, two studies involved healthy volunteers, 13 were limited to patients with possible coronary artery disease, and two included patients with atrial fibrillation. One study examined patients undergoing calcium scoring, while another looked at the pulmonary veins. Another study assessed coronary artery bypass grafts, and a final study examined a combination of these different patient groups.

The authors executed a three-level analysis to determine the prevalence of patients with extracardiac findings, followed by the prevalence of patients with significant cardiac findings, and finally the prevalence of patients with verified cancer.

Across all 19 studies, the prevalence rate for detecting an incidental extracardiac abnormality was 44% (95% confidence interval [CI]: 35%-54%) or about one in every 150 patients scanned.

However, the data was crippled by a high heterogeneity that challenged efforts to explain it by analyzing the subjects. Some studies had large findings of extracardiac, while others had very few. The prevalence rate for the detection of a major incidental extracardiac finding was 16% (95% CI: 14%-20%).

The authors estimated that several determinants, particularly different levels of attention given to detecting incidental findings to begin with, played a key role in the diversity of prevalence rates.

The prevalence became more consistent and predictable when detecting incidental cancers rather than just findings, especially for previously unknown cancers.

The collected cancer prevalence for 10 studies that included 5,082 patients was 0.7% (95% CI: 0.5%-1.0%), with almost ideal homogeneity, the authors noted. The 29 reported malignancies included 21 (72%) lung cancers, three thyroid cancers, two breast cancers, two liver cancers, and one mediastinal lymphoma.

"From an epidemiologic and clinical point of view, our results pointed out that performing cardiac CT implies a nonnegligible probability to diagnose a previously unknown cancer, which can be compared with that observed in recent CT trials for lung cancer screening, ranging from 0.3% to 2.7%, depending on population characteristics such as age, sex, and smoking history," said the authors.

One other helpful point is the fact that numerous risk factors for lung cancer echo those for coronary artery disease; thus, "referring physicians, patients, radiologists, cardiologists, and cardiac surgeons should be aware that when cardiac CT is performed, a collateral screening for extracardiac malignancies, mostly lung cancers, is being performed as well," the study team wrote; with some findings warranting instantaneous attention.

"For approximately 0.5% to 1% of patients undergoing cardiac CT, an incidental extracardiac finding may be immediately more important than a high calcium score or a coronary artery stenosis," Flor and colleagues wrote.

"This prevalence of incidental extracardiac findings implies a relevant issue for the medical profession: Cardiac CT deserves careful analysis and reporting by radiologists who should have both cardiac and thoracic (lung) CT expertise. As an alternative, if cardiologists report on only the 'cardiac' CT study, a second review should be performed by a thoracic radiologist, resulting in a double cost to healthcare systems for reporting cardiac CT results."

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