December 2, 2009 (Chicago, Illinois) — The low doses of radiation associated with annual screening mammography could be placing high-risk women in even more jeopardy of developing breast cancer, particularly if they start screening at a young age or have frequent exposure, according to new research presented here at the Radiological Society of North America 95th Scientific Assembly and Annual Meeting.

A meta-analysis of 6 studies found that women with BRCA1 or BCRA2 gene mutations or a family history of breast cancer who were exposed to radiation, either from mammography or chest x-rays, before the age of 20 had a risk for breast cancer that was 2.5 times higher than their counterparts who were not exposed to radiation (95% confidence interval [CI], 1.9 - 3.2).

The analysis, which examined 9420 high-risk women, also found that 5 or more mammograms increased risk 2.5-fold (95% CI, 1.6 - 3.9), Marijke C. Jansen-van der Weide, PhD, from the University Medical Center Groningen in the Netherlands, reported.

Overall, exposure to low-dose radiation increased breast cancer risk by a nonsignificant 1.5 times, compared with no exposure, Dr. Jansen-van der Weide said.

The mean age of the women in the analysis was 45 years. The cumulative dose of radiation they received ranged from 0.3 to 24 mSv.

"The take-home message here is that high-risk women who are younger should be careful about mammography screening," she told Medscape Radiology. "Because they are young, they also have dense breasts, which poses a problem with mammography. They should explore alternative screening methods."

The average woman has a 10% chance of developing breast cancer during her lifetime. In comparison, women who are carriers of the BRCA1 gene mutation have a 57% chance, and BRCA2 carriers have a 49% chance of developing breast cancer. Screening these women must start at an early age, since many will get breast cancer in their 30s or 40s, Dr. Jansen-van der Weide said.

Magnetic resonance imaging (MRI) could be one alternative for these women, although it has its own problems, she suggested. "MRI is not as readily available, it takes more time, and it is associated with many more false-positives. This is why it is so important for high-risk women to discuss the issue with their doctor and, together, work out a screening strategy."

She emphasized that screening mammography is not a problem for high-risk women 30 years and older. "Screening these high-risk women is still very important, but we must think about alternative nonionizing techniques at younger ages," she said.

"From our study results, we are talking about women below the age of 20, which is very young. We are also talking about 5 or more exposures. So if a woman starts at 25 and then gets 5 or more mammograms by the time she is 30, her risk will be increased. Up to the age of 30, women should be careful. After 30, perhaps she could do mammography screening every other year; that is one idea. We only used 6 studies in our analysis and we need more prospective studies to find out more about this."

The dangers of radiation in younger women have been well recognized, affirmed Allen G. Meek, MD, from State University of Stony Brook in New York, who moderated the scientific session.

"The general consensus is that the immature breast is more susceptible to ionizing radiation, so I certainly think that low-dose radiation is an issue."

He agreed that women should consider the risks and benefits and discuss them with their doctor. "The benefit is to catch the cancer earlier; the risk is you may be inducing the cancer."

Dr. Meek told Medscape Radiology that the study will make people more conscious about using a nonionizing method such as MRI. He suggested that mammograms not be done in women younger than 25 or 30 years, and then after the age of 30, a strategy might be to do a mammogram every other year, alternating with MRI.

"We know that the BRCA gene is a radiation repair gene, and when you are missing that, you have a decreased capacity for radiation repair, which will make you more susceptible to the low dose of radiation with mammography. We think this might be the biological basis for what this study found."

Dr. Jansen-van der Weide and Dr. Meek have disclosed no relevant financial relationships.

Radiological Society of North America (RSNA) 95th Scientific Assembly and Annual Meeting: Abstract RO22-04. Presented November 30, 2009.