Breast cancer treatment and how genetic testing helps

Getting diagnosed with breast cancer is an overwhelming experience. Decades of research means there are lots of different tests, medicines, and acronyms to understand. Thankfully, this also means that people with breast cancer have more choices when it comes to their treatment.

Genetic and genomic testing are different tests that can help to understand your cancer. Learn the difference between them and their role in your cancer journey, including deciding the best treatment for you. 

Cancer is caused by mistakes in your DNA. Sometimes these mistakes, also called ‘mutations,’ come from your parents, which means you’ve had those errors since you were born. Others develop during your life and can be caused by substances that harm your DNA, like chemicals in cigarette smoke.

Some gene mutations make you more or less likely to respond to certain treatments. Cancer medicines can have unpleasant side effects, so it’s helpful to know in advance whether it’s worth having the treatment.

Breast cancer treatment isn’t one-size-fits-all. Genetic and genomic testing are both important in personalising your treatment journey, which isn’t just about the stage and type of cancer you have. A personalised treatment plan should also consider your age, your health, and what’s important to you in your cancer treatment.

For example, you might want to explore your options for keeping your breasts or minimising the risk to your fertility. Our personalised breast cancer care includes genetic testing to build your treatment around you.

Although genetics and genomics testing sound similar, they look at different things. A genetic test looks at normal cells to test for genes that increase your risk of breast cancer. A common type of genetic testing in breast cancer looks for mutations in the BRCA gene, called BRCA1 and BRCA2 alterations.

Genomic testing looks at gene expression on the cancer cells. It’s sometimes called gene expression profiling (GEP). These tests provide an in-depth picture of your cancer and tell us about the DNA changes that could be driving the cancer. Currently, genomic testing for breast cancer is used to understand the risk of the cancer coming back, which helps to decide on treatment options such as chemotherapy or radiotherapy.

Looking at your genes isn’t used to diagnose cancer, and it doesn’t guarantee whether you’ll get cancer or if your cancer will come back. Instead, genetic tests are used to personalise your treatment so you can minimise your side effects and aim for the best possible outcomes. 

When you’re diagnosed with breast cancer, your doctor will help you decide the best option for you. For some people, genomic testing is part of this. It’s not always applicable, as the treatment pathway tends to vary with different types of cancers.

Genomic testing is particularly helpful for people with early breast cancer and in those with oestrogen receptor positive and HER2-negative breast cancer. Usually, the tests help to decide whether chemotherapy is recommended after surgery.

For example, the Oncotype DX genomic test looks at 21 different genes to estimate the risk of your breast cancer coming back in the next ten years. It gives you a score which predicts whether having chemotherapy will benefit you. For those at high risk, chemotherapy gives a better chance of destroying the cancer so that it doesn’t come back - making it worth the side effects of the treatment.

There are other tumour profiling tests that look at the biology of the tumour cells to see whether certain treatments could help. One example is the DCISionRT test, which helps to decide whether patients with non-invasive breast cancer could benefit from radiotherapy.

Genetic testing can look for mutations in the BRCA gene, which are linked to breast or ovarian cancer. When your BRCA genes are normal, they protect you from getting cancer by suppressing the growth of tumours. That is the reason why people with BRCA mutations are more likely to develop cancer – some of the body’s natural defence against tumours have been weakened.

BRCA gene testing is carried out in people with and without cancer. If you don’t have a cancer diagnosis but you have a strong family history of breast cancer, then BRCA testing can tell you whether you have a higher risk of developing cancer. Some people do this to decide whether to have preventative treatments, like a mastectomy.

If you have a diagnosis of breast cancer, BRCA gene testing shows if you have inherited a mutation that contributed to your cancer. People with BRCA mutations may benefit from additional treatment with a drug called PARP inhibitor, which is a relatively new medicine shown to help people with BRCA mutations. 

Many people worry that they will have to have their breast removed (a mastectomy) or have chemotherapy if they are diagnosed with breast cancer. 

This isn’t always the case. Chemotherapy and mastectomy may be used for more advanced cancer, especially if genetic tests suggest that they’re needed. There are several other options for treating breast cancer effectively and safely, which can include: 

• Breast conservation surgery
• Radiotherapy
• Hormone therapy
• Immunotherapy

Learn more about how patients are treated at GenesisCare for Ductal carcinoma in Situ, Invasive breast cancer and Secondary breast cancer.