Cardiac Imaging May Raise Cancer Risk

Study Shows Potential Long-Term Risks of Scans Performed After Heart Attacks

Cardiac imaging procedures such as cardiac catheterization and nuclear scans that are frequently performed after heart attacks are increasing the radiation exposure of patients as well as their long-term cancer risk, new research indicates.

The study by scientists at McGill University Health Center and the Jewish General Hospital in Montreal examined data on 82,861 patients who had suffered a heart attack between April 1996 and March 2006 but who had no history of cancer.

Of all the patients, 77% underwent at least one heart procedure with low-dose radiation within a year of the heart attack.

Researchers say 12,020 cancers were detected in follow-up research and that two-thirds of the cancers affected the abdomen, pelvis, and chest areas. The median age of patients was 63, and 32% were women.

Louise Pilote, MD, PhD, MPH, of McGill University, says in a news release that researchers found “a relation between the cumulative exposure to low-dose ionizing radiation from cardiac imaging and therapeutic procedures after acute myocardial infarction and the risk of incident cancer.”

The researchers write that their findings “call into question whether our current enthusiasm for imaging and therapeutic procedures after acute myocardial infarction should be tempered.”

They say doctors “should at least consider putting into place a system of prospectively documenting the imaging tests and procedures that each patient undergoes and estimating his or her cumulative exposure to low-dose ionizing radiation.”

Benefits vs. Risks

Study researcher Mark Eisenberg, MD, tells WebMD that the increased cancer risk caused by imaging tests may be outweighed by the immediate benefits of imaging procedures in preventing heart attacks.

He says the “chances of having a heart attack are higher than getting cancer” for most patients with heart disease symptoms whose doctors call for low-dose radiation procedures such as cardiac catheterization and nuclear scans.

Still, he says, the issue needs further study because a link between radiation exposure and increased cancer risk has been established by past research.

The researchers write that “little is known about the relation between exposure to low-dose radiation from medical procedures and the risk of cancer.” Nevertheless, an increase in recent years in the use of low-dose radiation tests “has led to a growing concern that individual patients may be at increased risk of cancer.”

The results of the study, the researchers write, “suggest that exposure to low-dose ionizing radiation directly affects the likelihood of cancer.”

Cardiac Images for Younger Patients

Heart patients are more likely to die of heart-related problems than of cancer, Eisenberg says, but still, the study found that exposure to radiation from heart imaging was associated with an increased risk of cancer.

“The message from our study is, there are small but finite risks associated with the radiation exposure,” he tells WebMD. “But because the imaging procedures are occurring more and more in North America, we should think more” about using the techniques.

“We have started to image people at younger and younger ages,” he says. “They have decades in which they can develop cancer.”

Mathew Mercuri, MSc, of McMaster University, says in a commentary published with the study that “the frequency with which such tests are performed may pose a population risk” and that doctors should consider using procedures with lower or no radiation if indicated.

“The benefits of such procedures tend to be evident,” he writes. “The risks, on the other hand, are not so apparent.”