Genetic testing for breast cancer

Genetic testing for breast cancer isn't just about your family tree. In fact, around 40 to 50% of women with a high-risk gene mutation have no known family history at all. I'm Giles Davies, a breast cancer surgeon, and today I want to help you understand how knowing your genetic risk could change your future. Understanding your genetic risk of future disease can help you take steps to reduce that risk and be screened regularly. There are several genetic tests available. The most well-known is BRCA testing, which checks for BRCA 1 and BRCA 2 mutations. These genes, when faulty, greatly increase the risk of breast and ovarian cancer. Although BRCA is a high risk gene mutation, there are other so-called 'medium penetrance genes' that carry lower but significant risks. Multi-gene panel testing - looks at many more genes, like PALB 2 and CHEK 2. A picture of these medium risk genes CAN indicate the need for regular earlier screening. Also, we are now able to sequence the whole genome. Whole genome sequencing is a test that reads all of your DNA — not just the parts that code for genes. It looks at your entire genetic blueprint to find any changes or mutations that might affect your health. It's powerful, but also complex - and not yet routine in NHS care. Another emerging tool is the polygenic risk score. This score adds up the small effects of many different genetic changes across your entire genome. Each of these changes on their own might not do much, but together, they can shift your risk higher or lower compared to the average person. So who should consider genetic testing? If you've had breast cancer under age 50, or if there's a family history of breast, ovarian, pancreatic, or prostate cancer, testing may be worthwhile. And if you're of Ashkenazi Jewish ancestry, the risks are significantly higher. If a test does show you carry a high-risk mutation, there are steps we can take—together. These include earlier and more frequent screening, risk-reducing medications, and, in some cases, preventative surgery. Preventative surgery, like a mastectomy or oophorectomy, is a choice made over time with professional support, and information. But for some women, it can reduce cancer risk by 90 to 95%. It's a deeply personal decision, made with support and guidance. There are also medications, like Tamoxifen, Raloxifine and Anastrozole, that can reduce the risk in women with certain gene mutations. Small lifestyle changes—like maintaining a healthy weight, not smoking, and regular exercise—can help too. Importantly, if you test positive, your close relatives may also carry the same mutation. They'll have the chance to be tested and make informed choices for their own health. We also now use genetic results to tailor cancer treatment itself. For example, BRCA-related cancers may respond better to drugs like PARP inhibitors. But these treatments will be guided by your specific mutation. Genetic testing is about knowledge, not labels. It's about being proactive. If you're unsure where to start, talk to your GP or breast specialist. We can guide you through testing options, counselling, and what your results might mean. Understanding your genetic risk allows you to make informed decisions about screening, and to focus on prevention and your overall health. It means you're informed, supported, and ready to take action—whatever that looks like for you. Many thanks for watching. And if you have any questions please don't hesitate to get in touch. We're never more than a phone call away.