Low Secondary Cancer Risk from CT Scans

Despite increasing radiation doses and reliance on CT scans in diagnosis and treatment, the risk for secondary cancers is low among older adults, according to a study published in the April issue of the Journal of the American College of Radiology.

Evidence shows that use of multi-detector CT scans (MDCT) provide better diagnosis and disease management, but there has been concern that the increased use may cause secondary cancers from the radiation, particularly among older patients who most frequently undergo the scanning.
Researchers from Stanford University in Stanford, Calif. undertook a retrospective cohort study using Medicare claims spanning eight years. Using two cohorts (1998 to 2001 and 2002 to 2005), the researchers found that although scans of the head were the most common, abdominal imaging delivered the greatest proportion of radiation (43 percent in the first cohort, and 40 percent in the second).

In the first cohort, 42 percent of patients underwent CT scans, with 2.2 percent and 0.5 percent receiving radiation doses in the low and high ranges, respectively. In the second cohort, 50 percent of patients received CT scans, with 4.2 percent and 1.2 percent receiving doses in the low and high ranges.

“Combining both low-risk and high-risk patient groups (50-100 and >100 mSv), as well as those who received <50 mSv, we estimate that 1,659 cases of cancer (0.03 percent of the study population) will develop in the 1998 to 2001 cohort and 2,185 (0.04 percent of the study population) in the 2002 to 2005 cohort,” according to Aabed Meer, AB, author of the study.

The continued rise of such imaging use and radiation exposure call for more research to limit ill effects, researchers said.

“Although modern CT imaging is a vital part of medical care, its utilization must include a conscious acknowledgment of radiation exposure and an awareness of the pursuant carcinogenic risk. As medical care continues its dependence on advance technologies, such as MDCT, we emphasize the importance of continuing research that encourages the exploration of lower radiation dose technologies,” Meer concluded.