A study 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.