Computerized simulation models suggest that lifetime risk of cancer associated with radiation exposure from computed tomography coronary angiography varies widely, with risk greater for women and younger patients, according to an article in the July 18 issue of the Journal of the American Medical Association.

Attempts to improve diagnosis of coronary artery disease have led to development of noninvasive methods including 64-slice computed tomography coronary angiography (CTCA). It has been predicted that computed tomography may emerge as the diagnostic test of choice for patients with intermediate pre-test probability of disease, yet there are little data on its associated cancer risk from exposure to radiation.

Andrew J. Einstein, MD, PhD, of Columbia University College of Physicians and Surgeons, New York, and colleagues conducted a study to estimate the lifetime attributable risk of cancer incidence associated with radiation exposure from 64-slice angiography and determine how risk is influenced by patient age, sex, and scan protocol.

The recent Biological Effects of Ionizing Radiation (BEIR) VII Phase 2 report provides a framework for estimating lifetime risk of cancer incidence associated with radiation exposure from CT angiography by using a computational model and integrating the most current data available on health effects of radiation.

Lifetime cancer risk estimates for standard cardiac scans varied from 1 in 143 for a 20-year-old woman to 1 in 3,261 for an 80-year-old man. Use of simulated electrocardiographically controlled tube current modulation (ECTCM; a dose reduction strategy that reduces radiation during part of the cardiac cycle) decreased risk estimates to 1 in 219 and 1 in 5,017, respectively.

Estimated cancer risks using current modulation for a 60-year-old woman and a 60-year-old man were 1 in 715 and 1 in 1,911, respectively. A combined scan of the heart and aorta had higher risks, up to 1 in 114 for a 20-year-old woman. The highest organ risks were for lung cancer and, in younger women, breast cancer.

“In this study, we observed a marked variation by age, sex, and scan protocol for cancer risk associated with radiation exposure from CT coronary angiography,” the authors wrote. “The results of this study suggest that CT angiography should be used particularly cautiously in the evaluation of young individuals, especially women, for whom alternative diagnostic modalities that do not involve the use of ionizing radiation should be considered, such as stress electrocardiography, echocardiography, or magnetic resonance imaging. If CT angiography is considered as an alternative to invasive coronary angiography, the risks and benefits of each test require consideration.”