Catheterizations, CT scans magnify radiation exposure in kids with heart disease

By Will Boggs MD

NEW YORK (Reuters Health) - Radiation exposure associated with repeated catheterizations and CT scans of some children with heart disease could double or triple their future cancer risk, according to research from Duke University.

"While children in our studies received many x-rays, these studies contributed a relatively small amount to their cumulative dose," Dr. Kevin D. Hill from Duke University Medical Center, Durham, North Carolina told Reuters Health. "More complex studies like CT scans and cardiac catheterization procedures were more significant contributors to cumulative radiation dose and associated risk."

Children with congenital and acquired heart disease typically undergo repeated imaging procedures that could expose them to large amounts of ionizing radiation. How much radiation they actually receive and how this could increase their lifetime cancer risk remains unknown.

Dr. Hill and colleagues estimated the cumulative effective dose of radiation exposure and its contribution to lifetime attributable risk of cancer in 337 children who underwent one of seven types of operations for congenital and acquired heart disease.

These children underwent a median of 17 examinations for a median cumulative effective dose of 2.7 mSv. This dose, overall, is less than the annual background exposure in the United States, according to the June 9th Circulation online report.

Children who had more complex heart disease and underwent cardiac transplantation or the Norwood operation received substantially greater cumulative exposure, though.

Transplant patients, for example, received a median posttransplantation cumulative effective dose of 45.8 mSv.

The contribution of radiation depended upon the type of imaging. Conventional x-rays represented 92% of the total examinations but accounted for only 8% of the cumulative effective dose. On the other hand, cardiac catheterizations represented only 1.5% of all examinations, but they contributed 60% of the total radiation exposure.

In fact, chest CTs accounted for the highest effective dose per study, followed by interventional catheterizations.

The lifetime attributable risk (LAR) of cancer also differed by imaging type. LAR per examination exceeded 350 cases per 100,000 children exposed to a chest CT and interventional catheterization, but only 0.2 cases per 100,000 children exposed to a portable chest x-ray.

Cancer risks were highest for children with the most complex heart disease. The median 10-year risk of any cancer was 3.2 times higher for the transplant group and 2.0 times higher for the Norwood operation group than for an unexposed population. These risks translate into a median 5-year sex-averaged all-cancer incidence (between ages 15 and 19 years) of 69.4 and 43.4 per 100,000 for the transplant and Norwood groups, respectively.

"We certainly aren't advocating that important imaging studies and procedures should not be performed in children," Dr. Hill said. "The benefits of these studies typically far exceed the risks. Catheterization procedures are increasingly used to avoid surgeries and some of the procedural advances have been incredibly beneficial for patients. However, I think provider awareness alone can have a tremendous influence on practice patterns."

"As an example, with some relatively simple measures, our catheterization laboratory and others across the country have significantly reduced radiation doses during cardiac catheterization procedures without compromising patient care," Dr. Hill added. "Radiologists have made similar improvements to CT imaging protocols. There are also times when physicians can choose between different types of studies."

"Finally I think it is important that providers inform parents of the risks associated with some of these studies," Dr. Hill said. "The risk on a per study basis is generally quite low, but parents have a right to know."

SOURCE: http://bit.ly/1kYISGi

Circulation 2014.

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