The study reviewed here found that women with an abnormal breast cancer gene (BRCA1 or BRCA2) who had five or more x-rays before they were 20 years old were 2.5 times more likely to develop breast cancer compared to women with an abnormal breast cancer gene who didn't have that many x-rays before the age of 20.
Women with an abnormal breast cancer gene who had five or more x-rays (including mammograms) after age 20 were 1.5 times more likely to develop breast cancer compared to women with an abnormal breast cancer gene who had the same number of x-rays, but after age 30.
To get these results, the researchers analyzed six earlier studies (called a meta-analysis) that looked at the relationship between x-rays and breast cancer risk in 9,420 women.
Women with an abnormal breast cancer gene have an increased risk of both breast and ovarian cancer over their lifetimes. The higher risk of breast cancer starts in early adulthood, so doctors recommend breast cancer screening start earlier for them -- age 30 for example -- than for women with average breast cancer risk. Still, doctors are concerned about the possible risks associated with radiation exposure from x-rays done at a young age.
When healthy cells are exposed to radiation, the radiation can damage genes in the cell. This gene damage can cause the cell to become cancer. Healthy cells do a good job of recognizing and repairing gene damage. But an abnormal BRCA1 or BRCA2 gene makes it harder for breast and ovarian cells to repair gene damage, including damage caused by radiation exposure. This is probably why the researchers found a higher risk of breast cancer in women with a history of x-rays before age 20.
Children, teens, and young adults may need x-rays for a number of reasons. Young people diagnosed with asthma or an orthopedic disorder may need x-rays as part of their care. And it's important for young women with an abnormal breast cancer gene to start being screened for breast cancer early in life. Still, the benefits of aggressive early screening must be weighed against the risk of recurring x-ray exposure.
The researchers who did this study wrote that starting mammogram screening at age 30 makes sense for most women at high risk. For some women at very high risk, starting screening at a younger age may be the best choice, but the benefits of earlier screening must be weighed against the risks. Women at high risk who start breast cancer screening at a younger-than-usual age may want to consider other screening techniques, such as breast MRI (which doesn't involve x-rays), to reduce the number of mammograms done.
The risks associated with x-ray exposure in this study apply ONLY to women with an abnormal breast cancer gene, NOT to women with average breast cancer risk. If you don't have an abnormal BRCA1 or BRCA2 gene and your breast cancer risk is average, the benefits of regular screening mammograms starting at age 40 are clear and aren't diminished by any risk of radiation exposure from the mammograms.
If you have an abnormal breast cancer gene, talk to your doctor and develop a breast cancer screening plan that weighs the benefits of starting regular screening mammograms at an earlier age against the risks of radiation exposure at a younger age. Breast MRI and breast ultrasound are other screening options that may decrease the number of mammograms you have during your lifetime. Still, while breast MRI is considered more sensitive than mammography in identifying breast cancer, it can miss some cancers that mammography would detect. That's why breast MRI typically is recommended only in combination with other tests, such as mammogram or ultrasound.
You can learn more about breast cancer screening for average-risk and high-risk women in the Breastcancer.org Screening and Testing section.
CHICAGO (MedPage Today) -- Some women already at high risk of breast cancer should be cautious about having mammography or chest x-rays before the age of 30 because the imaging may increase the risk of developing the disease, researchers here said.
Five or more x-rays, or any exposure to ionizing radiation before age 20, increased the likelihood of breast cancer two-and-a-half times in this high-risk group, Marijke C. Jansen-van der Weide, PhD, of the University Medical Center Groningen in the Netherlands, and colleagues reported at the Radiological Society of North America meeting.
"For women at high risk for breast cancer -- those with high-risk mutations of a family history of breast cancer -- screening is very important, but a careful approach should be taken when considering mammography for screening young women, particularly those under the age of 30," Jansen-van der Weide said.
But she cautioned that the findings do not apply to the general population. Women who are at an increased risk of breast cancer have a mutation in a damage-repair gene, which makes them more susceptible to the effects of DNA-damaging ionizing radiation. Most women do not have this mutation.
To assess how low-dose radiation exposure affects breast cancer risk, the researchers conducted a meta-analysis of six studies -- half of which showed an increased risk of cancer, and half that didn't -- totaling 9,420 women.
They found that high-risk women had a 2.5-fold increased risk of developing breast cancer compared with women in the general population (95% CI 1.6 to 3.9).
Those who had x-rays before they were 20 also had a 2.5-fold increased risk of developing breast cancer (95% CI 1.9 to 3.2).
And while x-ray screening after 20 carried a 1.5-fold increased risk of breast cancer, it was not significant, Jansen-van der Weide said.
"For high-risk women, it is important to screen for breast cancer," she said. "But they should weigh the risks and benefits with their doctors to come up with a screening strategy."
Jansen-van der Weide recommended starting screening at age 30, and going back every other year. Also, the possibility of using alternative techniques, such as magnetic resonance imaging (MRI), may be appropriate for high-risk women in this age group.
She called for future prospective studies to get a more accurate estimation of cancer risk from radiation exposure.
Mary C. Mahoney, MD, of the University of Cincinnati Medical Center and vice president of public information for RSNA, said the study deals with a very small population of breast cancer patients, "only 5% of all breast cancers."
"These tumors are biologically different," Mahoney said. "They're much more susceptible [to radiation exposure]."
She emphasized that the findings do not apply to the general population.
Stephen Feig, MD, of the University of California Irvine, a spokesperson for RSNA, said the study has many limitations, including its retrospective nature which did not permit a good analysis of radiation doses.
The researchers reported no disclosures.
Primary source: Radiological Society of North America meeting Source reference: Jansen-van der Weide, MC "Mammography Screening and Radiation-induced Breast Cancer among Women with a Familial or Genetic Predisposition: A Meta-analysis" RSNA Meeting 2009; Abstract RO22-04.
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