Negative BRCA Test not Reliable for Lower Chance of Breast Cancer

Kathleen Blanchard's picture
Researchers warn women who test negative for BRCA mutation still at high risk for breast cancer.
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In a study published in the journal Cancer Epidemiology, Biomarkers & Prevention, a journal of the American Association for Cancer Research, researchers warn women with the BRCA1 or BRCA2 gene mutation in their family who test negative still have more than quadruple the risk of developing breast cancer, compared to the general population.

Gareth R. Evans, M.B.B.S., M.D., M.R.C.P., F.R.C.P., honorary professor of medical genetics and cancer epidemiology at the Manchester Academic Health Science Center at the University of Manchester in the United Kingdom said in a press release: "We also found that any increased risk for breast cancer is largely limited to BRCA2 families with strong family history and other genetic factors.

According to Evans, the reason breast cancer risk is still higher for some women is likely from other BRCA-related genes that have yet to be identified.

What the finding means for women and clinicians

The finding means caution should be taken when telling women who test negative for the BRCA gene that their breast cancer risk is the same as other women in the general population. For women with a strong family history of breast cancer, it may not be true, the authors say.

Nancy Eliot, MD explains more about the BRCA1 and BRCA2 mutations that were discovered in the 1990s.

The study

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For their study, researchers used data from the M6-Inherited Cancer in England study that included families with breast cancer history who were screened for the BRCA1 and 2 mutations.

Forty-nine of the women developed breast cancer. Among the women, 22 out of 279 had tested negative for the BRCA gene mutations.

Next Evans and colleagues calculated the "observed versus expected ratio" of breast cancer risk among the women, compared to the general population.

They discovered women from families with the BRCA1 mutation were at no higher risk for developing breast cancer than other women. But for those with BRCA2 family history risk of the disease was more than four times higher from having a family history, even though the women tested negative for the gene.

"About 77 single nucleotide polymorphisms [SNPs -- genetic variations that can help track the inheritance of disease genes within families] are linked to breast cancer risk. Identification of additional SNPs is necessary to understand why some of the BRCA-negative women from BRCA families are at higher risk," Evans says.

Women that test negative for BRCA2 should continue to be screened regularly for breast cancer and engage in healthy lifestyle choices to mitigate their chances of the disease. Lifestyle factors that are known to lower a woman's chance of breast cancer include limiting alcohol intake, maintaining normal body mass index, regular exercise, breastfeeding, abstaining from smoking tobacco and avoiding or limiting hormone therapy.

Citation:
Cancer Epidemiology, Biomarkers & Prevention
Nov. 27, 2013
doi: 10.1158/1055-9965.EPI-13-0316-T

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