Family History and Breast Cancer Risk
By now, you’re probably aware that a family history of breast cancer can increase your own risk of getting the disease. With high-profile figures such as Angelina Jolie going public with their decision to undergo preventative surgery as a result of being genetically predisposed to getting breast cancer, we’re becoming much more aware of the role of genes when it comes to our health.
However, understanding your risk and knowing what to do about it can seem complicated and daunting, so we caught up with Gareth Evans, our professor of clinical genetics, to find out his responses to a few frequently asked questions.
What are genes and how can they determine my risk of breast cancer?
“We inherit our genes from our parents and, essentially, they tell our bodies how to grow and perform. There are about 25,000 genes that allow our bodies to develop and work, and DNA – a very long code – makes up each one of these genes. Nearly every disease we know of has a genetic element: from time to time, variations, or ‘mutations’, in the code can alter the way a gene works and therefore lead to the development of a disease, such as breast cancer.”
What are the frequently tested mutations that predict breast cancer risk and are there any others?
“The genes in which mutations are most frequently tested for are BRCA1 and BRCA2, which when present indicate a very high risk of getting breast cancer. They can increase your lifetime risk of developing the disease to between 40 and 85 per cent. These gene mutations affect about 0.5 per cent of the population and account for around 15 to 20 per cent of the underlying inherited genetic trigger for breast cancer.
“There are a handful of other genes in which mutations give you an equivalent high risk, but these are mostly extremely rare so aren’t always tested for, and then there are some more common variations we can test for which indicate a moderate risk, including ATM and CHEK2.
“Here in Manchester, we’ve been working with 18 other genetic variations called SNPs, which can help us predict with better accuracy which women are at increased risk of breast cancer. For example, we could use this test to provide women with the BRCA1 or BRCA2 mutation with a much narrower risk prediction, such as ‘between 40 and 45 per cent’ or ‘between 70 and 80 per cent’, as opposed to ‘up to 85 per cent’.
I have a family history of breast cancer. Should I see my doctor?
“Currently, for your family to qualify for BRCA testing, you must have either two close relatives (mother, sister, aunt or grandma) who were diagnosed with breast cancer under the age of 40; three close relatives who were diagnosed under the age of 50; or one relative diagnosed with breast cancer and one diagnosed with ovarian cancer. If you fit one of these, we’d recommend going to see your doctor.
“In order to carry out the testing, we usually require an affected person – a relative who’s had the disease – to test on, too. However, if there is no affected person available, you may still qualify for testing if the family link is even stronger.
“As a result of the testing, you may find out that you have a BRCA1 or BRCA2 gene mutation, or another high-risk variation, or combination of other lower risk ones. Sometimes, though, it may simply be that your family has been unlucky and there is no known genetic factor at play. At Prevent Breast Cancer, we’re conducting a number of studies as part of our wider PROCAS project to identify even more genetic influencers that increase a woman’s chances of getting breast cancer. We’re also delving deeper into other factors such as diet and lifestyle and those that affect breast density, a major indicator for breast cancer risk.”
What options are available to me depending on my risk?
“Depending on your risk level, you’ll be offered a variety of risk-reducing measures. If you’re deemed to be high risk, you’ll be offered annual mammograms – as opposed to the standard three-yearly screens – between the ages of 40 and 60. You’ll also be eligible for preventative drugs, such as tamoxifen or anastrozole. When it comes to the BRCA1 and BRCA2 gene mutations, a woman’s risk is so significantly increased that, in this instance, some consider having a preventative mastectomy, but this is an extreme measure and it’s important to think about other options.
“You’re considered to be moderate risk if your mother or sister was diagnosed with breast cancer under the age of 40, or if two close relatives on the same side of your family were affected under the age of 60. In this case, you’ll be offered annual mammograms between the ages of 40 and 49, and will also be considered for preventative drugs.
“If you’re at lower risk, having standard mammograms every three years while maintaining a healthy weight would be appropriate.
“Whatever your risk, it’s important to carry out regular self-checks to keep on top of your breast health and spot any changes early.”
How do I work out what’s best for me?
“Choosing which route to go down based on your risk is a completely personal thing and each woman’s journey is different. If you’re told you’re at moderate or high risk, it can seem quite overwhelming, but your doctor will discuss all of the options available to you and help you reach a decision that you’re happy with.”
Interested in gene research? Take a look at our current studies to find out more.