The Institute of Medicine (IOM) issued a review of all available scientific data related to the environmental risks of breast cancer, and while the report investigated a number of consumer products linked to the disease, the most significant conclusion was that exposure to ionizing radiation is one of the leading environmental factors most strongly associated with breast cancer, according to an analysis of IOM’s findings published online June 11 in the Archives of Internal Medicine (AIM).

"The single thing that the IOM highlighted that a woman can do to lower her risk of breast cancer is to avoid unnecessary medical imaging," Rebecca Smith-Bindman, MD, a professor of radiology and biomedical imaging, epidemiology and biostatistics at the University of California, San Francisco, said in a release. Smith-Bindman wrote the AIM article and contributed to the IOM report, which was commissioned by the Susan G. Komen for the Cure breast cancer foundation.

Smith-Bindman specifically cited CT use as an area for improvement. Although it can be a highly valuable tool for physicians, unnecessary CT use may lead to small but real increases in cancer risks, and patients should play a role in the decision to undergo imaging. "They should understand the risks and benefits and ask their doctor to explain the risks and benefits,” she said.

Despite the risks, CT overuse still occurs. Physicians like the modality for the ease in which exams are conducted and the clear diagnostic images that result, wrote Smith-Bindman, but stronger pressures toward overutilization are found by following the money.

“Intense marketing focusing on profit leads to the rapid purchase of machines prior to completely understanding how this technology should be used to improve health outcomes has created excess capacity, complicated by few evidence-based guidelines for its use. Strong financial incentives, reflected by the growing ownership of CT scanners by nonradiologists for use in their private medical offices, strong patient demand (in part resulting from direct-to-consumer advertisements that do not mention untoward effects), and medical malpractice concerns leading to defensive test ordering, have all further contributed to high excess use.”

Excess radiation exposure is aggravated by large variations in CT doses between institutions, explained Smith-Bindman. Inadequately trained technologists and poorly designed equipment also can lead to dosing errors.

“A reduction in variation in doses across patients and institutions and elimination of overdosing errors would greatly improve the safety of CT and reduce its potential for causing cancer,” wrote Smith-Bindman.

She called for greater oversight of CT, and noted that the National Quality Forum adopted a quality measure asking facilities to record CT doses. Smith-Bindman also noted that while CT manufacturers are creating new devices that use lower doses of radiation, they should also work with facilities currently using existing equipment to offer software upgrades that can help manage dose.

“The IOM estimated that 2,800 future breast cancers would result from one year of medical radiation exposure among the entire U.S. female population, with two-thirds of those cases resulting from CT radiation exposures. While these represent a small proportion of all breast cancers, they are important because they can potentially be reduced.”