Women at hereditary risk for breast cancer who receive mammograms or chest X-rays before age 30 may be at higher risk for the disease, European research suggests.

The women at greater risk are those who carry a mutation in two genes.The BRCA1 and BRCA2 genes control the suppression of breast and ovarian cancer.

"BRCA genes help repair DNA damage — damage which can be caused by exposure to radiation like X-rays," study author Prof. Douglas Easton of Cancer Research UK said in a release.

"Women with faults in these genes are less able to repair damage caused by radiation, so they are at a greater risk of developing breast cancer. It’s important that these women and their doctors are aware of this."

Women with BRCA1 or BRCA2 are at high risk for breast cancer and are often screened at an earlier age. About two per cent of breast cancers are caused by BRCA mutations.

'No one should think that they should never get an X-ray because they have the BRCA1 or 2 gene mutations.'— Dr. Len Lichtenfeld

In Britain, the Netherlands and Spain, doctors advise women under 30 with BRCA mutations to get magnetic resonance imaging or MRIs to screen for breast cancer instead of risking radiation exposure from mammograms.

The findings of a study in this week's issue of the British Medical Journal support that approach.

Investigators followed 1,993 women with BRCA 1 or BRCA2 mutations in Britain, France and the Netherlands.

The women recalled previous chest X-rays and mammograms, when and how often.

"In this large European study, exposure to diagnostic radiation before age 30 was associated with an increased risk of breast cancer in BRCA1/2 mutations, at dose levels considerably lower than those at which increases have been found in other cohorts exposed to radiation," the study's authors concluded.

MRI option

About 43 per cent of the women in the study were diagnosed with breast cancer.

The researchers estimated that for every 100 women aged 30 with a mutation, nine will develop breast cancer by age 40. Another five would be added if all had a mammogram before age 30. The average age at first mammogram for the study participants was 29.5.

Radiation after age 30 did not seem to affect breast cancer risk.

The researchers acknowledged limitations of the work, including reliance on self reports rather than reviewing medical records. Also, the amount of radiation varies for different machines, hospitals and diagnostic procedures.

In Canada, breast cancer screening guidelines for women at high risk vary by province. Cancer Care Ontario's high-risk guideline suggests annual combined mammography and breast MRI for ages 30 to 69. Similarly, Alberta Health Services recommends MRI in addition to mammography every 12 months for women at high risk.

Dr. Len Lichtenfeld, deputy chief medical officer of the American Cancer Society, said the findings will raise questions about how women with BRCA mutation are treated.

"No one should think that they should never get an X-ray because they have the BRCA1 or 2 gene mutations," he said. "Just be careful that the X-rays you get are really the ones that you need."

Lichtenfeld was not involved in the research.

The study was funded by European cancer groups.

With files from The Associated Press