What risk factors are
Anything that increases your risk of getting a disease is called a risk factor. Different cancers have different risk factors. This page discusses the risk factors for breast cancer. Even if you have one or more of the risk factors below, it does not mean that you will definitely get breast cancer.
Like most cancers, the risk of developing breast cancer increases as women get older. As we get older the cells in our body have had more chance to make mistakes when they were dividing. So it is important to have mammograms as part of the national breast screening programme as soon as you are old enough.
The UK screening programme sends invitations for screening to all women aged between 50 and 70. They are extending this to cover women from the ages of 47 to 73. You won’t be invited to go for mammograms after you reach the age of 71, but you can ask your local breast cancer screening office to carry on inviting you every 3 years.
Having a mother or sister diagnosed with breast cancer approximately doubles the risk of breast cancer. But more than 8 out of 10 women who have a close relative with breast cancer will never develop it.
If several members of your family have had particular types of cancer or if a relative was diagnosed with breast cancer at a young age, your risk of developing breast cancer may be increased further.
The National Institute for Health and Clinical Excellence (NICE) has guidelines that identify family histories that could increase your risk of breast cancer. If you fit these criteria, your GP should refer you to a specialist breast clinic for assessment.
NICE classify women into 3 groups. Under this system, you may have a moderate risk of breast cancer, a high risk, or the same risk as the general population of women (a low risk). NICE say that moderate risk means you have at least a 1 in 6 risk of getting breast cancer by the end of your life. When compared to the risk of the general population, you may have some increase in breast cancer risk if you have ONE of the following in your family
A mother or sister diagnosed with breast cancer before the age of 40
2 close relatives from the same side of the family diagnosed with breast cancer – at least one must be a mother, sister or daughter
3 close relatives diagnosed with breast cancer at any age
A father or brother diagnosed with breast cancer at any age
A mother or sister with breast cancer in both breasts – the first cancer diagnosed before the age of 50
1 close relative with ovarian cancer and 1 with breast cancer, diagnosed at any age – at least one must be a mother, sister or daughter
The affected relatives must come from the same side of your family (either your mother’s side OR your father’s side) and they must be your blood relatives. A close relative means a parent, brother or sister, child, grandparent, aunt or uncle, nephew or niece.
These are only guidelines. The breast care team work out your risk of developing breast cancer using your family history and individual factors. After assessment some women may be told that their risk is much the same as the average woman. If your risk is found to be high, the breast team may offer you an appointment with a genetic counsellor to help you understand more about your risk. They will also offer you information about genetic testing.
If your doctor or genetic counsellor think you have a raised risk of breast cancer you will be offered screening which may include yearly mammograms and possibly MRI scans.mammograms. The screening you will have depends on Your age How dense your breasts are (if your breast tissue is dense it can make reading mammograms more difficult)
Your risk of developing breast cancer, that is whether you have a moderate or high risk
What your risk is of having a particular gene change is if you haven’t had a test
Whether you have had a test which has shown a genetic change
You can read the NICE guidance on the care of women with breast cancer in the family. There is detailed information about breast screening and who should be referred in this section.
If you are worried that several members of your family have had breast or ovarian cancer, the best thing to do is talk to your GP. If you like, you could print off this page and take it with you.
Breast cancer genes
If you have a very strong family history, there may be a faulty gene in your family that increases your risk of breast cancer. There are probably several gene faults that can increase breast cancer risk. We can test for 2 of them, BRCA1 and BRCA2. Your risk of getting breast cancer by the age of 80 if you have either of these breast cancer gene faults is between 45 to 90%.
Having one of these faulty genes means that you are more likely to get breast cancer than someone who does not have the gene fault. But it is not a certainty. It is also possible to test for the faulty TP53 gene and PTEN gene, which are much rarer than BRCA mutations, but can increase the risk of breast cancer. In this section there is information about breast cancer genes, getting tested, and your options if you have a faulty gene.
Remember that most breast cancers happen by chance. Only about 3 out of every hundred (3%) are related to a known inherited breast cancer gene. The older that you or your relatives are when diagnosed, the less likely it is that an inherited gene is the direct cause.
Sex hormones and other hormones
The female sex hormone, oestrogen, and the male hormone, testosterone, can affect the development of breast cancer. Women tend to have small amounts of the male hormone testosterone in their bodies. Studies generally show that after their menopause women with higher levels of oestrogen and testosterone in their blood have a 2 to 3 times higher risk of breast cancer than women with the lowest levels of these hormones.
Before the menopause, levels of oestrogen vary during the menstrual cycle and studies have not shown clearly that these hormones affect the risk of breast cancer in this group of women. Many of the major risk factors for breast cancer can be explained through their effect on hormone levels.
Studies also show an increased risk of breast cancer in with higher levels of a hormone called insulin like growth factor 1 (IGF-1). We are not sure what controls levels of IGF-1 in the bloodstream, but it is probably related to our genes, body weight, and how much exercise we do.
Hormone replacement therapy (HRT)
Many women in the UK take hormone replacement therapy (HRT) to reduce menopausal symptoms. There are 2 main types of HRT – combined HRT (oestrogen and progesterone) and oestrogen only HRT.
In 2003, researchers from Cancer Research UK looked at HRT and the risk of breast cancer in more than a million women. They showed clearly that HRT increases the risk of breast cancer while women take it and for up to 5 years afterwards. Other studies have also confirmed this. The million women study also showed that combined HRT (oestrogen and progesterone) is more likely to cause breast cancer than oestrogen only HRT.
A study published in December 2011 estimated that just over 3 out of 100 breast cancers in women in the UK in 2010 were linked to HRT use. This relates to around 1,530 cases. About 3 out of 4 of these extra breast cancers are linked to the use of combined oestrogen and progesterone HRT. And 1 out of 4 are linked to oestrogen only HRT.
HRT can have some health benefits and so if you are worried about taking it, you can talk to your doctor about the benefits and risks in your individual situation.
There is detailed information about HRT and breast cancer risk in the question and answer section.
The contraceptive pill
The combined pill contains oestrogen. Oestrogen can stimulate breast cancer cells to grow. In theory, taking extra oestrogen could trigger a breast cancer to develop. Several large studies have looked at whether the pill can increase the risk of breast cancer. The overall picture seems to be that there is a small increase in risk while you are taking it. But the increase in risk goes back to normal 10 years after you’ve stopped taking it. Balanced against this, the pill also seems to reduce the risk of some other cancers, such as ovarian and womb cancers.
We don’t really know if taking the pill increases the risk of breast cancer for women who have a family history of breast cancer. Some research says that it may increase breast cancer risk in these women. Other studies have found that it makes no difference. So we need more research to find this out.
It can be difficult to make sense of all this research. It is important to remember that breast cancer is rare in young women and the age groups most often using the pill are women in their late teens, twenties and early thirties. So a small increase in this risk during the time women take the pill means very few extra cases of breast cancer.
Having children or having them early in life
Women who have children have a slightly lower risk of breast cancer than women who don’t have children. And the risk reduces further the more children you have. Your age when you have your first child also has an effect. The younger you are when you have your first child, the lower your risk.
When you start and stop having periods
Starting your periods (menarche) at an early age has been linked with an increased risk of breast cancer. And if you have a late menopause this increases your breast cancer risk.
Statistical surveys in America and England have shown that white women have a higher risk of breast cancer than women from other ethnic groups. This is at least partly due to lifestyle factors.
A previous breast cancer
We know that a woman who has had breast cancer has an increased risk of getting breast cancer in the other breast. Your specialist knows that too and will keep a close eye on you. If you do get a breast cancer in the other breast, it should be picked up quickly.
You will have some protection against getting another breast cancer if you are taking hormone therapy to lower the risk of your breast cancer coming back.
DCIS and LCIS
DCIS stands for ductal carcinoma in situ. This is when breast cancer cells are completely contained within the breast ducts and have not started to spread into the surrounding breast tissue. It is sometimes called pre invasive breast cancer. LCIS stands for lobular carcinoma in situ. It means there are some abnormal cells in the lobules of the breast.
Studies show that women with a diagnosis of DCIS or LCIS have a risk of invasive breast cancer in the same or other breast that is approximately double that of women in the general population. One study showed that women with a previous carcinoma in situ of the breast have a 16% (about 1 in 6) risk of developing breast cancer within 10 years. But, even so, most women with LCIS or DCIS will not develop cancer.
High grade DCIS and a type of LCIS called pleomorphic LCIS are more likely to develop into breast cancer than other types of DCIS or LCIS. If you do have LCIS or DCIS, your doctor will want you to have check ups regularly afterwards. There is information about LCIS and DCIS in this section.
Benign breast disease
There are 3 types of non cancerous (benign) breast conditions
1. Non proliferative 2. Proliferative without atypia 3. Proliferative with atypia (atypical hyperplasia) Breast disease that is not growing and where the cells are not dividing is called non proliferative and does not usually increase the risk of breast cancer. But if you have a strong family history of breast cancer it may increase the risk by a small amount.
Breast lumps with an overgrowth of cells (proliferation) but without abnormal (atypical) cells double the risk of breast cancer compared to the average risk.
About 1 in 20 breast lumps (5%) show atypical hyperplasia. This means the cells are not cancer, but are growing abnormally. Atypical hyperplasia increases your risk of breast cancer by more than 4 times the average. Atypical hyperplasia is uncommon and if you haven’t been told that your breast lump showed these changes, it probably didn’t. But if you are worried, you can ask your doctor to check the biopsy result and let you know.
You should always get breast lumps checked out immediately to make sure they are not cancer.
Having dense breast tissue
Breast tissue density relates to how your breast tissue shows up on a mammogram. Women with dense breast tissue have less fat and more breast cells and connective tissue in their breasts. Because they have a greater proportion of breast cells, the risk of breast cancer is higher.
A recent overview of studies (meta analysis) reported that women with the most dense breasts had almost five times the risk of breast cancer of women with the lowest density. There is some evidence that ultrasound can be a useful test alongside mammography for diagnosing breast cancer in women with dense breasts. Breast ultrasound may be able to pick up a breast cancer that a mammogram has missed. MRI scans may also be helpful in finding cancers in denser breast tissue in younger women.
Alcohol intake and smoking
Drinking alcohol has been shown to increase the risk of breast cancer. Two large combined reviews of the published evidence and the UK Million Women Study showed an increase in risk of about 7 to 12% with every extra unit of alcohol per day. One unit is a half pint of beer, a small glass of wine, or a measure of spirits. To be on the safe side, it is best for women not to drink more than 14 units of alcohol per week.
There is information about research into alcohol and breast cancer in the questions and answers section.
There is limited evidence that smoking may be linked to breast cancer in women who started smoking before the age of 20 or before the birth of their first child.
Your weight and height
Weight and height can both affect your breast cancer risk.
Weight is a bit confusing. If you are overweight before you’ve had your menopause, your risk of breast cancer is lower than average. But if you are overweight after menopause, your risk of breast cancer is higher than average. This is because women who are overweight ovulate less than average. So their breast cells may be exposed to lower levels of oestrogen. But after the menopause, your oestrogen levels are linked to the amount of body fat you have. The more fat you have, the higher your oestrogen levels are likely to be.
Taller women have an increased risk of breast cancer after the menopause. It’s not clear why this is, but taller women may have more breast tissue, which might increase the risk.
Chest X-rays or radiotherapy
Exposure to radiation is known to increase the risk of many types of cancer. But most of this research has been in people who have been exposed to a lot of radiation, due to an atomic bomb explosion or a radiation accident. There is known to be a slight increase in risk in people who work with low doses of radiation over a long period of time – for example, X-ray technicians. But most of us are never exposed to enough radiation to make much difference to our risk.
Nowadays, doctors keep medical exposure to radiation as low as possible. They don’t do X-rays or CT scans unless they really need to. And the amount of radiation used to take an X-ray or scan is very small, and lower than it used to be.
Chest X-rays give a very low dose of radiation and researchers estimate that around 60 cases of breast cancer in the UK each year are linked to diagnostic X-rays. Doctors balance this very small risk with the need to diagnose illness so that it can be properly treated. If you had a lot of chest X-rays in the past and are worried, talk to your doctor.
Many women worry that having mammograms as part of breast screening exposes them to X-rays. But the amount of radiation used to take a mammogram is very small. The increase in risk is tiny compared to the benefit of finding and treating a breast cancer early. Many things we do expose us to slight increases in radiation (such as flying in a plane) but we don’t always think it sensible to stop doing them.
Radiotherapy treatment for breast cancer increases the risk of getting breast cancer in the other breast by a small amount. But this small risk is balanced by the need to treat the original breast cancer.
If you had radiotherapy to your chest for Hodgkin’s lymphoma in the past, you could be at increased risk of getting breast cancer. This applies to all women treated as children or in their 20s. The radiation affects your breast tissue. There probably isn’t an increase in risk for the first 5 or 10 years after your Hodgkin’s treatment. But there is after that.
If you need radiotherapy for Hodgkin’s lymphoma your doctors will tell you about this risk. They will offer you breast screening if it is appropriate. There is detailed information about breast cancer risk after Hodgkin’s in our question and answers section.
An overview study (meta analysis) of 20 individual studies reported that women with diabetes have a small increase in their risk of breast cancer. This may be due to higher levels of insulin during the initial phase of diabetes. But people with diabetes often have a higher body mass index (BMI) and a high BMI increases the risk of breast cancer for some people. So it is not clear why women with diabetes may have an increased risk. Post menopausal women treated for diabetes with a medicine called metformin have a lower risk of breast cancer than women who don’t have that treatment.
Research has found that taking high blood pressure medicines for longer than 5 years increases the risk of breast cancer by a fifth. People treated for an overactive thyroid gland (Graves’ disease) also have an increase in breast cancer risk.
Women have an increased risk of breast cancer if they took a drug called diethylstilbestrol during pregnancy between the 1940s and 1960s. Diethylstilboestrol is an oestrogen like drug that is no longer used. Doctors gave it from 1945 to about 1970 to women who were at risk of miscarriage.
Some studies have shown that women who do night shift work have a slight increase in breast cancer risk. Other studies show that sleeping longer reduces the risk of breast cancer. Some researchers think this may be because broken or shorter periods of sleep lowers levels of a hormone called melatonin.
What you can do
Unfortunately there is little we can do about some of these risks, apart from be aware of them. But you can be aware of breast changes to look out for. And it is important to attend for breast screening tests when you are invited.