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Is breast cancer risk increased in BRCA-mutation negative women?


This research is relevant for:

Unhecked Breast cancer survivors

Checked Women under 45

Checked Women over 45

Unhecked Men with breast cancer

Unhecked Metastatic breast cancer

Unhecked Triple negative breast cancer

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Unhecked BRCA mutation carriers

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Unhecked Her2+ breast cancer

Checked Special populations: Women who test negative for the BRCA mutation in their family

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Some women who do not carry a BRCA mutation, but come from a BRCA-positive family, still develop breast cancer. This research examines whether these women are at higher risk for breast cancer, or whether their risk is similar to women in the general population. (4/19/16)


STUDY AT A GLANCE

This study is about:

Whether women from BRCA mutation-positive families who test negative for their familial BRCA mutation are at higher risk of breast cancer than women in the general population.

Why is this study important?

If women who test negative for the BRCA mutation in their families are at higher risk than women in the general population, they may require different screening or prevention.  

Study findings: 

  1. Women who tested negative for their familial BRCA2 mutation were almost 5 times more likely to develop breast cancer than expected for an average-risk woman of the same age.

What does this mean for me?

More research needs to be done to understand if women who do not carry the BRCA mutation found in their family are still at higher risk of breast cancer than women in the general population. Even if you don’t test positive for your family’s mutation, having a first-degree relative who has had breast cancer raises your risk for developing the disease compared to women in the general population. Patients from high-risk families should speak with a genetics expert before and after genetic testing to understand their risk for cancer and determine a screening program that is appropriate for them.

Questions to ask your health care provider:

  • I do not carry my family’s BRCA mutation. What type of cancer screening should I have?
  • I developed breast cancer even though I do not carry my family’s BRCA mutation. What is my daughter’s risk?
  • What are risk factors for breast cancer?
  • How can I reduce my breast cancer risk?

IN DEPTH REVIEW OF RESEARCH

Study background:

Researchers have noted the development of breast cancer in women who do not carry their family’s BRCA mutation. Researchers studied whether these women may have increased risk for breast cancer, even though they do not share their family’s BRCA abnormality.

In December 2013, Gareth Evans and his colleagues from the University of Manchester and other institutions published an article that examined whether women who tested negative for a familial BRCA mutation were at increased risk for breast cancer. Published over two years ago, the study raised a still controversial question regarding appropriate care for women who test negative for a BRCA mutation but are from a BRCA-positive family, as this is still an area of uncertainty.

Researchers of this study wanted to know:

Whether a woman with a negative BRCA test result may have increased risk of breast cancer if she is from a family that carries a BRCA mutation.

Population(s) looked at in the study:

This study included only first-degree relatives (parent or sibling) of BRCA mutation carriers in 809 families (428 BRCA1 families and 381 BRCA2 families).

Study findings: 

  1. Women who tested negative for their familial BRCA2 mutation developed breast cancer about 4.5 times more than expected for women of their age. Within this population, 14 breast cancers developed at the follow-up time, rather than the 3 that were expected.
    • This result was statistically significant, meaning that the result did not occur by chance, and was more likely to be a real finding.
  2. Women who tested negative for their familial BRCA1 mutation developed breast cancer about 1.8 times more than expected for women of their age. Within this population, 7 breast cancers developed at the follow-up time, rather than the 4 that were expected.
    • This result was not statistically significant, meaning that it may have occurred by chance, and may not have been a real finding. 

Limitations:

Women in this study who tested negative for BRCA may have been screened much more than women in the general population. Increased MRI or mammography could have resulted in more cancers being caught. Additionally, we have not identified and cannot always test for every gene that can affect cancer risk within families—abnormalities in other genes may influence risk in families with BRCA mutations. This study only looked at whether the women carried BRCA mutations; it did not consider whether they might have carried other genetic mutations that raise cancer risk. This is important, because if the BRCA-negative women who developed breast cancer carried mutations in other genes, their cancers could be attributed to those other mutations. Finally, this study was conducted through a cancer genetics clinic, a type of clinic that often sees families with very high cancer rates, which may have biased the results.

Conclusions:

The study authors wrote: “In the context of a family BRCA2 mutation, especially when there are multiple close relatives affected with early-onset breast cancer, specialists should advise that breast cancer risks may still be increased compared with the general population.” However, this is the result of only one study. Other work involving this issue has resulted in the exact opposite conclusion: that a woman with a BRCA-negative test result for her family mutation is not at higher risk for breast cancer. Currently, the NCCN has no clear guidelines regarding care for women in this population, and more work is needed to understand the cancer risk for women who do not carry their familial BRCA mutation. This underscores the importance of genetic counseling by a genetics expert to determine what screening is appropriate for each individual woman.

References

Evans GR, Ingham SL, Buchan I, et al. “Increased Rate of Phenocopies in All Age Groups in BRCA1/BRCA2 Mutation Kindred, but Increased Prospective Breast Cancer Risk Is Confined to BRCA2 Mutation Carriers.” Cancer Epidemiology, Biomarkers & Prevention. 2013 December; 22(12): 2269-2276.

Kurian AW, Gong GD, John EM, et al. “Breast cancer risk for noncarriers of family-specific BRCA1 and BRCA2 mutations: findings from the Breast Cancer Family Registry.” Journal of Clinical Oncology. 2011; 29:4505-4509.

Posted 4/19/16

Related Information and Resources

Joining FORCEs Newsletter: Weighing the Evidence: Are Women Who Test True Negative for BRCA at Increased Risk of Cancer?

Joining FORCEs Newsletter:  Phenocopy Hypothesis

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