Don't rush past that word "may." The researchers aren't totally certain of their findings, so they're not giving any advice just yet.
The data need to be confirmed "before definite clinical recommendations can be made," write Nadine Andrieu, Ph.D., and colleagues. Andrieu works for France's National Institute of Health and Medical Research (Institut National de la Sante et de la Recherche Medicale).
But if the findings are correct, then an MRI might be a better imaging option than mammography for some women at high genetic risk for breast cancer, states a journal editorial.
Breast Cancer Gene Mutations
Andrieu's study focused on women with the BRCA1 and BRCA2 gene mutations, which greatly raise the risk of breast and ovarian cancers.
The BRCA1 and BRCA2 gene mutations are rare; they're carried by an estimated 250,000 U.S. women, according to the Susan G. Komen Breast Cancer Foundation Web site. Inherited gene mutations account for 5 percent to 10 percent of breast cancers diagnosed in the U.S., according to the foundation.
Here's how the Komen Foundation puts the risk in perspective: "A woman's odds of developing breast cancer in her lifetime (assuming she lives until the age of 85) are a bit over 13 percent if she does not have a BRCA1 or BRCA2 mutation, 60 percent to 80 percent if she has a BRCA1 mutation, and 30 percent to 85 percent if she has a BRCA2 mutation."
Other gene mutations may also affect breast cancer risk.
Breast Cancer Study
Andrieu's study included 1,601 European and Canadian women with the BRCA1 or BRCA2 gene mutations. The group included 853 women with breast cancer.
When the women were about 47 years old, on average, they completed questionnaires that asked how many chest X-rays — not counting mammograms — they had had before and after age 20.
About a quarter of the women reported no chest X-rays, while 970 women noted at least one chest X-ray. Data about chest X-rays was missing for the remaining participants, who made up about 15 percent of the entire group.
Interpreting The Results
The results show that the women who reported any chest X-rays were 54 percent more likely to have breast cancer, compared with those reporting no chest X-rays. That pattern was strongest for women up to 40 years old and those who reported having had chest X-rays before age 20.
Radiation exposure can raise the risk of cancer. X-rays typically use low levels of radiation that are generally considered to be safe.
The BRCA1 and BRCA2 gene mutations may be particularly vulnerable to radiation, write Andrieu and colleagues. However, they didn't check the women's medical records to confirm their X-ray history.
"These results must be interpreted with caution," note the researchers, who also don't know how much radiation the women received from the chest X-rays. Andrieu's team stresses that more detailed data, preferably from long-term studies, are needed before recommendations can be made.
Their study didn't address X-rays and breast cancer in women without the BRCA1 and BRCA2 gene mutations.
The journal also includes an editorial by the University of Chicago's Angela Bradbury, M.D., and Olufumilayo Olopade, M.B., B.S., FACP.
"The limitations of this report, including the imprecise measurement of radiation exposure and the potential for differential recall among participants, lessen the clinical relevance of the study," write Bradbury and Olopade. "It is likely that the impact of radiation-associated breast cancer is small to nonexistent among women who begin standard mammographic screening at 40 years old, but we do not know if this is also the case for women at high genetic risk."
If women at high genetic risk for breast cancer are more affected by X-ray radiation, an alternative to mammography might be MRI, which uses different imaging technology than X-rays. However, "there is currently not enough evidence to replace mammography with breast MRI," write the editorialists.
They call for more work to clarify the risks and benefits of X-rays for young women, whose dense breast tissue may affect mammography screening, and all women at high genetic risk of breast cancer.
SOURCES: Andrieu, N. Journal of Clinical Oncology, June 26, 2006; early online edition. Susan G. Komen Breast Cancer Foundation: "BRCA1/BRCA2 and Breast Cancer." Bradbury, A. Journal of Clinical Oncology, June 26, 2006; early online edition. News release, American Society of Clinical Oncology.
By Miranda Hitti. Reviewed by Louise Chang, MD
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