RSNA: Mammo may increase breast cancer in high-risk women; turn to MRI
CHICAGO—Low-dose radiation increases breast cancer risk among young women with a familial or genetic predisposition and, therefore, characterized as high-risk, according to a meta-analysis presented Tuesday at the 2009 Radiological Society of North America (RSNA) conference. Researchers recommended MRI for these patients.

Lead author Marijke Jansen-Van Der Weide, PhD, from the department of epidemiology and radiology at the University Medical Center Groningen in the Netherlands, stressed that the study focused on high-risk patients and that these findings come from a retrospective meta-analysis, so “we need more prospective studies to obtain a more accurate assessment of [radiation-related] breast cancer risk among high-risk patients.”

Women who are at high risk for breast cancer need to begin screening at a younger age, because they often develop cancer earlier than women at average risk. However, according to Jansen-van der Weide, young women with familial or genetic predisposition to the disease may want to consider alternative screening methods to mammography, because the benefit of early tumor detection in this group of women may be offset by the potential risk of radiation-induced cancer.

In general, she said that moderate to high doses of radiation are an established risk factor for development of breast cancer; there is an inverse relationship between age at exposure and risk of radiation-induced breast tumors; and higher doses present a higher risk. She noted that it takes 10 to 20 years for such a cancer to manifest itself.

The researchers conducted an analysis of peer-reviewed, published medical research to determine if low-dose radiation exposure affects breast cancer risk among high-risk women. Out of 47 articles found on the topic, six were selected by the reviewers for inclusion in their analysis. Four studies looked at the effect of exposure to low-dose radiation among breast cancer gene mutation carriers, and two studies researched the effect of radiation on women with a family history of breast cancer.

Using data from these studies, the researchers were able to calculate pooled odds ratios to estimate radiation-induced breast cancer risk.

Jansen-van der Weide explained that the study showed that among all high-risk women in the study, average increased risk of breast cancer due to low-dose radiation exposure was 1.5 times greater than that of high-risk women not exposed to low-dose radiation. High-risk women exposed before age 20 or with five or more exposures were 2.5 times more likely to develop breast cancer than high-risk women not exposed to low-dose radiation.

"Our findings suggest that low-dose radiation increases breast cancer risk among these young high-risk women, and a careful approach is warranted," Jansen-van der Weide said.

She reiterated that women at average risk were not assessed in this study.

As mammographic screening doubles breast cancer risk among high-risk women, she concluded, it is important to be careful with the use of low-dose radiation, especially at a young age, and to avoid repeated exposure.

Jansen-van der Weide recommended that future prospective studies are needed for more accurate estimation of effect. She added that younger high-risk women should weigh benefits and risks together with their doctors, but they may want to consider the use of alternative techniques, such as MRI.