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EBCC-11: Risk of a Second Breast Cancer Can Be Better Quantified in Patients With a BRCA Mutation

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Key Points

  • Polygenic risk scores may be able to predict the risk of a second breast cancer in BRCA breast cancer survivors.
  • The difference in the risk of a second breast cancer between different polygenic risk scores can be up to 10% in the 10 years following a first diagnosis. 

The risk of a second breast cancer in patients with high-risk BRCA gene mutations can be more precisely predicted by testing for several other genetic variants, each of which are known to have a small impact on breast cancer risk, according to new research presented at the 11th European Breast Cancer Conference (EBBC-11) (Abstract 7).

Patients with breast cancer who are diagnosed at a very young age or who have a strong family history of the disease are regularly found to carry a mutation in either the BRCA1 or BRCA2 gene. They are also at high risk of developing a second cancer in their other breast, and may opt for a double mastectomy to reduce their risk.

Technology already exists to test for these genetic “low-risk variants” that each play a small role in breast cancer risk. The new research shows that this technology can also be used for BRCA mutation carriers who have already had one cancer to better predict their risk of developing a tumor in the other breast. The research was presented by Alexandra van den Broek of the Netherlands Cancer Institute in Amsterdam. She explained, “Women with a BRCA mutation are more likely to develop breast cancer when they are young and, unfortunately, some will be unlucky and go on to suffer a second breast cancer later in life. We know these women are at a higher risk, but it has also been shown that individual risks may vary widely, so we wanted to see if there was any way to better identify patients at lower and higher risks.”

Study Findings

The researchers studied a group of around 6,000 patients with breast cancer who had a mutation in the BRCA1 gene and around 4,000 who had a mutation in BRCA2. The women were from countries around the world, including The Netherlands, Spain, the U.K., the U.S., Australia, and Canada.

The team used existing technology to examine the low-risk variants that each woman carried. The effects of all these variants were put together to give each person a combined estimate known as a polygenic risk score.

The results showed that these polygenic risk scores may be able to predict the risk of a second breast cancer in BRCA breast cancer survivors. The difference in the risk of a second breast cancer between different polygenic risk scores can be up to 10% in the 10 years following a first diagnosis. 

Dr. van den Broek added, “These polygenic risk scores were originally developed to try to better predict the risk of developing a first breast cancer. Our research suggests that they can also be used to help patients who have survived their first breast cancer to better understand their level of risk for a second breast cancer. We hope these findings will add to the existing knowledge about predicting risk for a second breast cancer in these survivors.”

The researchers will continue to study the significance of these low-risk variants and how they interact with other known risk factors, such as age. They acknowledged that their findings could be influenced by the fact that women with a second breast cancer are more likely to be tested for a BRCA mutation, which may mean they are overrepresented in this study. They also said that validating the results in an independent cohort would strengthen their findings.

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.


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