Radiation exposure from x-rays, mammograms, and other diagnostic tests prior to age 30 may increase the risk of breast cancer in women who carry BRCA1 or BRCA2 mutations, according to the results of a large, retrospective cohort study published in the British Medical Journal.
Inherited mutations in two genes—BRCA1 and BRCA2—have been found to greatly increase the lifetime risk of developing breast and ovarian cancer. Mutations in these genes can be passed down through either the mother’s or the father’s side of the family.
A mammogram is an X-ray of the breast. Screening mammography is performed in a woman without breast symptoms in order to detect breast cancer at an early stage when it is most easily treated. Currently, mammography is the most reliable tool for screening the general population for breast cancer and may even reduce the risk of death from breast cancer (due to early detection). Mammograms are most often used in women over the age of 40; however, women who carry BRCA mutations are considered high-risk and may benefit from earlier and more frequent screening. This earlier screening can come with the added risk of increased radiation exposure—and exposure to ionizing radiation, especially when it occurs at an early age, is an established risk factor for breast cancer.
To examine the relationship between radiation exposure and breast cancer risk among BRCA1/2 mutation carriers, researchers from Europe followed nearly 2,000 women over age 18 with a BRCA1 or BRCA2 mutation. The women reported their history of procedures—such as x-rays or mammograms—that involved radiation to the chest or shoulders. The researchers then used this information to estimate the cumulative dose of radiation to the breast for each woman and compared this against confirmed breast cancer diagnoses among the women.
When compared with no exposure, any exposure to chest radiation prior to age 30 was associated with almost double the risk of breast cancer in BRCA1/2 mutation carriers. Exposure prior to age 20 was associated with a 62 percent increased risk. Women who received the highest doses or radiation prior to age 30 had almost four times the increased risk. In contrast, there was no evidence of an increased risk of breast cancer associated with exposure after age 30.
The researchers concluded that exposure to diagnostic radiation before age 30 among carriers of BRCA1/2 mutations was associated with an increased risk of breast cancer. What’s more—the increased risk of breast cancer was observed at radiation doses considerably lower than those associated with an increased risk among other populations.
Because women with BRCA1/2 mutations have an increased risk of developing breast cancer, some guidelines recommend earlier screening; however, the results of this study may indicate that BRCA1/2 carriers under age 30 might benefit from surveillance that uses non-ionizing radiation imaging, such as magnetic resonance imaging (MRI).
Pijpe A, Andrieu N, Easton DF, et al. Exposure to diagnostic radiation and risk of breast cancer among carriers of BRCA1/2 mutations: retrospective cohort study (GENE-RAD-RISK). British Medical Journal. 2012; 2012;345:e5660
Posted October 2, 2012