Chicago ? High-risk women who rely on mammograms as a weapon against breast cancer may actually increase their chances of getting the disease, according to preliminary research released Monday.

The study looked at 1,600 European women with genetic mutations that predispose them to get breast cancer. Women who reported having had at least one chest X-ray were 54 percent more likely to develop breast cancer than those who had never had one.

This Catch-22, reported in the current issue of the Journal of Clinical Oncology, means women with mutations in BRCA1 or BRCA2 genes might want to consider being screened with magnetic resonance imaging instead of X-rays, doctors said.

It also suggests that women and men with a family history of breast or ovarian cancer might want to consider genetic testing to find out if they carry a mutation before they get any X-rays to the chest area, doctors said.

Exposure to ionizing radiation – the kind that comes from nuclear fallout as well as from X-rays – is known to cause breast cancer. But the risk is small enough for the vast majority of women over 40 that experts still recommend annual screening mammograms.

In women under 40, mammograms are less accurate and the radiation is potentially more dangerous. But those are precisely the women most at risk for hereditary breast cancer.

“Maybe after age 30 the risk of cancer is high enough to justify the potential long-term risk of cumulative radiation,” said Dr. Olufumilayo Olopade, director of the cancer risk clinic at the University of Chicago Medical Center. “So we traditionally recommend that high-risk women – especially mutation carriers – start screening with mammography at 25.

“This (study) calls into question, is it possible by starting so young we might increase their risk?”

MRI could eventually become the preferred screening tool for high-risk women, said Olopade, who wrote an editorial accompanying the study. But it’s not a perfect solution.

MRI alone can be hard to read and can have a high rate of false-positive results, which lead to unnecessary biopsies, said Dr. Virginia Kaklamani, an expert in breast cancer and cancer genetics at Northwestern University.

So, if a radiologist found something suspicious on an MRI, she said, “I’d probably recommend a mammogram” despite the radiation exposure.

“Until we have more research,” Kaklamani said, “younger women with a genetic susceptibility to breast cancer are between a rock and a hard place.”

David Goldgar, a genetic epidemiologist at the University of Utah and lead author of the study, said it was too soon to draw conclusions about who should or should not have screening mammograms. He said further research was needed to confirm the results.

The study “is not enough to mandate changes in clinical practice,” said Dr. Kathy Albain, director of the breast research program at Loyola University Medical Center in Maywood, Ill. “But I think it’s enough to modulate our recommendations for certain patients.

“If you have very young patients who are also BRCA carriers, maybe you don’t send them for a chest X-ray at the first cough,” she said.

Kaklamani said women known to be mutation carriers might also think twice about getting mammograms before age 35.

The European study did not look at breast X-rays, but the radiation exposure to breast tissue with a mammogram is significantly higher than the exposure with a standard chest X-ray.

The researchers hypothesized that radiation might be particularly dangerous for BRCA mutation carriers because those genes are believed to be responsible for repairing DNA damage. Defective genes would be less able to repair the damage caused by radiation.

Dr. Lydia Usha, who runs the RISC (Rush Inherited Susceptibility to Cancer) Center at Rush University Medical Center in Chicago, said more high-risk women might decide to have prophylactic mastectomies – surgical removal of both breasts – if the study results are confirmed. Most patients don’t choose that option now.