Chest x-ray may increase likelihood of breast cancer

An analysis of 1600 women with BRCA1 and BRCA2 mutations suggests that exposure to chest x-rays may increase the risk of breast cancer. Exposure before the age of 20 may be linked to particularly heightened risk.

The research, conducted by a consortium of European cancer centers, was the first to analyze the impact of low-level x-ray exposure among women at genetically high risk for the disease. The study was published online on 26 June in the Journal of Clinical Oncology.

"This is one of the first studies to demonstrate that women genetically predisposed to breast cancer may be more susceptible to low-dose ionizing radiation than other women," said lead author David E. Goldgar, Ph.D., chief of the genetic epidemiology group at the International Agency for Research on Cancer in Lyon, France, at the time the research was conducted.

If findings are confirmed in prospective studies, young women in families known to have BRCA1 or BRCA2 mutations may wish to consider alternatives to x-ray, such as MRI, Goldgar said.

Researchers analyzed questionnaire data completed by more than 1600 women who were involved in the International BRCA1/2 Carrier Cohort Study (IBCCS), a collaborative European study of women who carry BRCA1/2 mutations. While all the women were carriers, not all had developed breast cancer.

The questionnaire asked whether a woman had ever received a chest x-ray, whether she had received chest x-rays before the age of 20, after the age of 20, or during both periods, and how many x-rays she had been exposed to during each time frame.

The study found that women with BRCA1/2 mutations who reported ever having a chest x-ray were 54% more likely to develop breast cancer than women who had never undergone the procedure. Women who were exposed to x-rays before the age of 20 had a 2.5-fold increased risk of developing the disease before the age of 40, compared with women who had never been exposed.

"Since BRCA proteins are integral in repairing damage to breast cells, we hypothesized that women with BRCA1/2 mutations would be less able to repair damage caused to DNA by ionizing radiation," Goldgar said. "Our findings support this hypothesis, and they stress the need for prospective studies."

The investigators noted two primary limitations of the study. The first was the potential for recall bias, meaning that women who had developed breast cancer might be more likely to remember receiving an x-ray than women who had not been diagnosed with the disease. The second was the lack of data on the specific dose and timing of radiation that was received.