Study measures cancer risk from cardiac CT scans

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Doctors often order a cardiac CT scan to determine whether patients are at risk for heart attack. While early detection of arterial blockage can save lives, CT scans also expose patients to X-ray radiation. The radiation itself bears some risk of cancer. A new study by doctors at Ohio State University and Mount Sinai Medical Center found a way to measure that risk.

Cardiac CT scans provide a high resolution image of the heart and coronary arteries. The technique has become increasingly popular worldwide. Sanjay Rajagopalan, a cardiologist at the Ohio State University Medical Center and senior author of the new study, says doctors need more detailed information about the risks inherent in the test itself.

“When we were doing this procedure we were a little bit disappointed because there was really no well published literature that provide people precise risk estimates of what their lifetime risk of cancer is,” Rajagopalan said.

It would take too long to determine the risk by following patients who had received CT scans. So Rajagopalan and his colleagues generated a model of the risk. They measured how much radiation is generated by a CT scan. Then they compared this radiation level to a national cancer risk database that includes radiation effects measured following events like the bombing of Japan during World War II.

Their calculations revealed that young women were at the greatest risk, because of the sensitivity of breast tissue to radiation, and because of the relatively long life span over which they could develop cancer following a scan.

Rajagopalan says that in many cases, the benefits of a CT scan would outweigh the small risks. He hopes that the study will allow doctors and patients to make more educated decisions as they consider diagnostic options.

“The important thing is that this paper I hope at least gets into some of the guidance documents of national societies that do these kinds of studies so that it really provides you very accurate risk estimates so if you’re asked a question what is my risk you can provide that and then it’s up to physicians to really balance those risk benefit questions on an individual basis,” he said.

The study appears in the current issue of the Journal of the American Medical Association.

Elsa Youngsteadt, WOSU News

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