Cancer genetics - breast cancer
Sometimes, women worry about getting breast cancer because a relative has had it.
Breast cancer is a common cancer - about 1 in 8 women in the UK will get it during their lifetime. If you have just one, or even two, elderly relatives diagnosed with breast cancer, it doesn’t mean you’re at a much increased risk yourself.
Most of the time, we don’t know exactly what causes any particular cancer. But we do know some of the risk factors for cancer. Risk factors are things that can make you more likely to develop cancer.
Some risk factors are very likely to cause cancer. Others only slightly increase the risk of getting it. Usually, cancer is the result of a combination of several risk factors.
Having a particular risk factor doesn’t mean that you’ll definitely get cancer - just as not having any risk factors doesn’t mean you won’t.
Smoking is a good example of this. If you smoke, it isn’t certain that you will get lung cancer - just as if you don’t smoke, it’s not certain that you won’t. But smoking will greatly increase your risk of getting lung cancer. About 9 out of 10 people who develop lung cancer are smokers.
For most people, increasing age is the biggest risk factor for developing cancer. In general, older people (those over 65) are far more likely to develop cancer than younger people (those under 50).
Cancer is very common. Most of us have relatives who’ve had cancer. People often worry that a history of cancer in their family greatly increases their risk of developing it. But in fact, fewer than 1 in 10 cancers (5-10%) are associated with a strong family history of cancer.
How does family history affect risk of breast cancer?
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Most breast cancers are not hereditary (caused by inherited cancer genes) and most women who get breast cancer don’t have a family history of it.
If you have one female relative who developed breast cancer over the age of 40, your risk is unlikely to be very different from other women the same age as you.
However, sometimes breast cancer can run in families. In general, the more members of your family who have been diagnosed with breast cancer (or related cancers such as ovarian cancer), the younger they were when diagnosed, and the more closely related they are, the more likely it is that there’s a family link.
Only a very small proportion of breast cancers (5–10%) are thought to be caused by a change (alteration) in a gene running in the family.
The two genes that are most often found to be altered in hereditary breast cancer are called BRCA1 and BRCA2.
If a family has an altered BRCA1 or BRCA2 gene, usually several relatives on the same side of the family are diagnosed with breast cancer or related cancers. People in the family may also be diagnosed with cancers at a particularly young age.
BRCA gene alterations are more common in certain populations. If you have Ashkenazi Jewish ancestry and have relatives who’ve been diagnosed with ovarian or breast cancer, you may want to discuss your risk with your GP.
If you’re concerned about your risk of breast cancer, visit your GP. They can talk to you about your family history and your risk.
We have an online tool you can use to assess your risk of genetic breast or ovarian cancer. OPERA (Online Personal Education and Risk Assessment) asks you about 10 questions before giving you a personalised assessment with further information and support. OPERA isn’t intended to replace professional advice, so you should still consult your doctor.
Assessing family history
A family history of cancer is usually based on your close relatives, which include your first-degree relatives.
First-degree relatives are your parents, brothers, sisters and children. Close relatives are your first-degree relatives and also your grandparents, grandchildren, aunts, uncles, nieces and nephews.
Examples of a family history that may mean you have an increased risk of developing breast cancer include having:
one first-degree relative who developed breast cancer under the age of 40
one first-degree male relative (father, brother or son) with breast cancer
one first-degree relative with cancer in both breasts
two close relatives (one of whom is a first-degree relative) on the same side of your family who developed breast cancer under the age of 60
three close relatives on the same side of your family who developed breast cancer at any age
breast and ovarian cancer on the same side of the family.
If any of the above apply to your family, or you’re worried about your risk, talk to your GP. They may be able to reassure you or refer you to a clinical genetics service or family cancer clinic.
A woman’s risk of breast cancer, based on her family history, may be estimated as average, moderate or high.
Average risk (near population risk)
This is also sometimes called population risk. It means your risk is the same or very similar to the risk of women who don’t have a family history of breast cancer. You’re more likely not to get breast cancer than to get it.
Moderate risk (raised risk)
This means your risk is higher than average but it’s unlikely that there is a breast cancer gene in the family. You are still more likely not to get breast cancer than to get it.
This means you have a high risk of developing breast cancer in your lifetime. However, it doesn’t mean that you’ll definitely get breast cancer. There may be a hereditary breast cancer gene in your family.
If your risk is moderate or high
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If you have an increased risk of developing breast cancer because of your family history, you’ll be offered additional breast screening.
Women with a moderate risk are offered yearly mammograms (breast x-rays) between the ages of 40 and 49.
Between the ages of 50 and 59, women either continue with yearly mammograms or have a mammogram every three years as part of the general NHS Breast Screening Programme. Your specialist will advise you on which option is appropriate for your situation.
From age 60 onwards, all women at moderate risk rejoin the NHS Breast Screening Programme and have a mammogram every three years.
Women at high risk are usually offered yearly mammograms. These may begin at age 30 or 40 and continue until age 59 or 69, depending on individual risk.
Some women will also have yearly MRI scans. The age women are first offered these scans depends on their estimated risk. Women who have an altered BRCA gene are offered MRI scans from the age of 30.
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Women at increased risk of breast cancer may choose to have treatments such as surgery or drugs that help reduce risk.
Risk-reducing surgery involves an operation to remove the ovaries or the breasts. This is a major step to take and is only suitable for a small number of women with a very high risk of breast cancer.
Having risk-reducing drug treatment involves taking a tablet, either tamoxifen or raloxifene, every day for five years. It’s estimated that this reduces breast cancer risk by 30%-40%. However, these drugs can cause side effects similar to the menopause such as hot flushes, vaginal discharge, urinary problems and weight gain. They also increase the risk of blood clots and womb cancer. The drugs aren’t suitable for women planning to get pregnant.
For most women with a high risk, the benefits of these drugs probably outweigh the risks. But women at moderate risk may have to think more carefully if they’re offered this treatment.
Before deciding whether to have any risk-reducing treatment, you should have time to talk through all the possible benefits and disadvantages with a genetics or breast cancer specialist.
Most women who develop breast cancer don’t have a strong family history of it. Other factors can play a more important role in the development of breast cancer.
The strongest risk factor for breast cancer is increasing age. About 8 out of 10 women diagnosed with breast cancer (80%) are over the age of 50. Nearly half of all breast cancers (45%) occur in women over the age of 65.
The female hormones oestrogen and progesterone can affect your breast cancer risk. Various things affect your exposure to these hormones, and therefore affect your breast cancer risk.
Your period and menopause
Starting periods at an early age (under 12) and having a late menopause (after the age of 50) may increase breast cancer risk.
Pregnancy and giving birth reduce the risk of breast cancer. The younger a woman is when she starts having children and the more children she has, the more her risk is reduced.
Breastfeeding reduces breast cancer risk. The longer a woman breastfeeds for, the more her risk is reduced. For general health reasons and to reduce breast cancer risk, women are advised to breastfeed if possible.
Taking the contraceptive pill slightly increases the risk of breast cancer. If you stop taking the pill, your risk reduces again. Ten years after stopping the pill, any excess risk will have gone.
Hormone replacement therapy (HRT)
Using HRT increases the risk of breast cancer. Both types of HRT (oestrogen-only and combined oestrogen and progesterone) can increase the risk. Once a woman stops taking HRT, her risk reduces again.
If you’re unsure about whether it’s okay for you to take the pill or use HRT, it’s best to discuss the benefits and disadvantages with your GP. They will be able to give you information and advice that takes account of your age, general health and personal risk of breast cancer.
Other breast conditions
Non-cancerous breast conditions are common and most don’t increase your risk of breast cancer, but a few can. They include:
These conditions may be discovered during tests to investigate a breast lump or during routine breast screening. If you have a breast condition that may increase your risk, your doctor can tell you whether you need treatment or more frequent breast screening.
Dense breast tissue
Breasts are made of fat, connective tissue and glandular tissue. Some women have more glandular and connective tissue and less fatty tissue in their breasts. This is known as dense breast tissue and can increase the risk of developing breast cancer. If you have dense breast tissue, this will show up on a breast x-ray (mammogram).
Women who have had radiotherapy to their chest before the age of 35 (for example, for Hodgkin lymphoma) have an increased risk of breast cancer. These women may be offered additional breast screening from the age of 25-50.
The risk of breast cancer is higher in women who are overweight after the menopause. It’s estimated that more than 8% of breast cancers in women in the UK are linked to being overweight.
Drinking alcohol increases your risk of developing breast cancer. The increase in risk is small for women who drink within the recommended guidelines (see below), but it increases steadily the more alcohol you drink. It’s thought that about 6% of breast cancers in the UK are linked to alcohol.
Women who work night shifts for many years (20 or more) may have a slightly increased risk of breast cancer.
There’s evidence that being less physically active increases the risk.
Smoking may cause a small increase in breast cancer risk. The earlier you start to smoke and the longer you smoke for, the greater the risk.
Up to 40% of cancers in the UK could be prevented by changes in lifestyle.
Keep to a healthy weight
The latest figures for the UK estimate that more than half of adults (61%) are overweight.
If you are overweight, getting back to a healthy weight will help reduce your risk of breast cancer after the menopause.
Leading an active lifestyle, following a healthy diet and controlling the size of your portions can help you maintain a healthy weight. Your GP can give you more advice on your ideal weight and on losing weight.
Eat a healthy diet
To reduce your cancer risk, eat plenty of fibre, such as beans, oatmeal, fruit and vegetables. Aim to eat five portions of fruit and vegetables every day.
Limit how much red meat and salt you eat and avoid processed meat. Processed meats are meats that have had preservatives added to them or have been preserved by salting, curing or smoking. They include sausages, ham and burgers.
Eating a healthy diet can also lower your risk of developing other illnesses such as heart disease and diabetes.
Limit how much alcohol you drink
Drinking alcohol increases your risk of breast cancer. The European Code Against Cancer recommends that to reduce cancer risk, women should drink no more than one unit of alcohol a day. A unit is half a pint of ordinary strength beer, lager or cider, one small glass (125ml) of wine, or a single measure (25ml) of spirits.
Keep physically active
Regular physical activity can help to reduce the risk of breast cancer. Being physically active doesn’t necessarily mean going to the gym - regular walking, cycling or swimming can be enough.
Try to do at least 2½ hours of moderate-intensity physical activity a week. This could be made up of 30 minutes of activity each day for five days. You could even break it up further into 10 minutes of activity, three times a day.
Moderate-intensity activity is where you’re still able to talk, but your breathing is quicker and deeper. Your body is warming up, your face may have a healthy glow and your heart is beating faster than normal but not racing.
If you’re not used to exercise, your GP can advise you on getting started.
Give up smoking
There is some evidence that smoking may increase your risk of developing breast cancer. It has been shown to increase the risk of many other cancers such as cancers of the mouth, throat, lung, bladder, cervix, kidney, pancreas, bowel and stomach. Smoking also increases your risk of heart disease and high blood pressure.
Smoking is the single biggest avoidable cause of cancer.
If you smoke, giving up is the most important thing you can do for your health. Help is available if you want to give up smoking. Ask your GP for advice, or contact your national stop smoking service.
Tel 0800 022 4332
(Mon-Fri, 9am-8pm, Sat-Sun, 11am-4pm)
Tel 0800 84 84 84
Stop Smoking Wales (Wales)
Tel 0800 085 2219
Smokers’ Helpline (Northern Ireland)
Tel 0808 812 8008
Making the lifestyle changes described above doesn’t mean that you definitely won’t get breast cancer, but it makes it less likely and will improve your health generally.
Get to know the normal look and feel of your breasts. Visit your GP if you notice any change that’s unusual for you.
When it’s found early, breast cancer can often be treated successfully.
In most cases, changes to your breasts don’t mean that you have cancer, but you should see your GP if you have:
lumps or bumpy areas in your breast
a change to the outline or shape of your breast
nipple discharge that is not milky
unusual discomfort or pain in one breast (breasts are often more tender or a bit lumpy just before a period).
Screening for breast cancer
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After the age of 50, women are invited to join the NHS Breast Screening Programme. This aims to detect breast cancer early when it’s easier to treat. Screening involves having a mammogram (breast x-ray) every three years until you reach the age of 70. Women aged 70 and over can continue to have regular mammograms by contacting their GP, who will arrange an appointment at a breast screening clinic.
There are plans to expand the breast screening programme in England from 2016, to include women aged 47-73.
Breast screening can help detect breast cancer early, when it’s most likely to be treated successfully.
If you are still worried
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A common reaction to serious illness in the family, or to bereavement, is to feel more vulnerable to the same disease. If you can’t stop worrying, you may find it helpful to speak to a counsellor. You can ask your GP for details of a local counselling service, or contact our cancer support specialists.
The mental health charity MIND has a leaflet called How to Stop Worrying. Order a copy from their website or by calling 0300 123 3393.