Many women worry about getting breast cancer, sometimes because one of their relatives has developed the illness. This section explains:

• Why having just one or even two relatives with cancer does not normally make it more likely that you will get cancer yourself.
• What we know about the causes of breast cancer.
• What you can do to help yourself.

The cause of most breast cancers is not known. But we do know that some things (called 'risk factors') increase our chances of developing cancer. If you have a particular risk factor for cancer, this does not mean you will definitely get cancer, just as not having it does not mean that you won’t get ill. It is about probability.

Smoking is a good example of this: if you smoke, it is not certain that you will get cancer. If you don’t smoke, it is not certain that you won’t. But if you smoke, your risk of getting lung cancer is far higher than if you don’t. Nine out of ten people who develop lung cancer are smokers.

Risk factors for breast cancer are not as clear-cut as smoking and lung cancer. But some risk factors have been identified.

Genes are the biological information you inherit from your parents. They affect the way your body grows, works and looks.  Changes (mutations) to these genes can increase the breast cancer risk of family members who inherit the genetic change. But only a small number of breast cancers (5–10% or less than 1 in 10 cases) are due to an inherited altered gene running in the family.

Two gene changes (called BRCA1 and BRCA2 mutations) can run in a family and increase the breast (and ovarian) cancer risk of those family members who inherit the genetic change. But this is very unusual.

It is only likely that a genetic mutation that can increase your breast cancer risk is present in your family, if you have:

• Three close relatives from the same side of the family who developed breast cancer at any age, or
• Two close relatives from the same side of the family who developed breast cancer under 60, or
• One close relative who developed breast cancer at the age of 40 or under, or
• Breast and ovarian cancer on the same side of the family or a male relative with breast cancer or a close relative with cancer in both breasts.

If your family is like this, and you are worried about developing breast cancer yourself, you might want to talk to your GP. If you have a family history of any unusual cancers/childhood cancers or you have Jewish or other ethnic background (where a faulty breast cancer gene is more common), you should mention that to your GP. Women who seem to have inherited an increased risk of getting breast cancer may be offered yearly mammograms from the age of 40. All women are invited to join the NHS Breast Screening Programme when they are 50.

If you only have one middle-aged or elderly relative who has developed breast cancer, or one case of breast cancer on each side of your family, this does not significantly increase your risk. If one of the breast cancer genes was running in your family, then it is likely that more than one relative would have developed breast cancer.

If you are still worried

It can be a normal reaction to severe illness in the family or to bereavement to feel more vulnerable to the same disease. If you can’t stop worrying, you may find it helpful to see a counsellor, who can help you get things back into perspective. You can ask your GP for details of a local service, or you can call the Cancer Counselling Trust or Cancerbackup.

MIND, the mental health charity, has published a useful leaflet called How to stop worrying.

Other risk factors can play a bigger role in the development of cancer than family history. For example, the main risk factor for breast cancer is age. Women under 50 are at far lower risk of getting breast cancer than older women. Women under 40 have a 1 in 200 chance of developing breast cancer (0.5%), but the risk rises to about 1 in 10 (10%) for all women under 80.

Hormone levels  There is some evidence that the more years a woman has had periods, and is therefore exposed to the female hormone, oestrogen, the more prone she is to breast cancer. This means that some possible risk factors have been identified:

• An early first period (under 12) 
• A late menopause (after 50) 
• No or late (over 30) childbearing
• No breastfeeding or breastfeeding for less than 12 months in total.

The contraceptive pill  The contraceptive pill slightly increases women’s risk of getting breast cancer. The risk decreases again after stopping the pill.

Hormone replacement therapy (HRT)  Combination hormone replacement therapy (HRT containing not just oestrogen) increases a woman’s breast cancer risk. The risk rises the longer HRT is taken, but again, it decreases when HRT is stopped. Five years after stopping, it is back to normal.

Obesity  Being overweight, particularly after the menopause, is a risk factor for breast cancer. This seems to be because overweight people have different hormone levels compared to people who are of normal weight.

Lack of exercise  There is evidence that regular exercise reduces women’s breast cancer risk. This might be because physical activity regulates women’s hormone levels.

Benign (non-cancerous) breast lumps and cysts  Having had a number of breast lumps or cysts increases a woman’s risk of getting breast cancer. But it is important to remember that most women who have had benign lumps or cysts do not develop breast cancer.

Alcohol  Drinking excessive amounts of alcohol seems to increase women’s breast cancer risk. It is recommended that women should drink no more than 14 units of alcohol per week. A unit is half a pint of ordinary strength beer, lager or cider or 1 small glass of wine or 1 single measure of spirits.

Other possible risk factors
There is no good evidence for claims that particular diets, or supplements or deodorants affect a woman’s breast cancer risk. Scientists are studying many different possible factors, but so far the risk factors listed above are the only ones for which there is good evidence.

We would all like to make sure that we stay healthy. However, the truth is that many of the known breast cancer risks are beyond our control. But it might make you feel better to avoid those risk factors that you have control over. You might want to:

• Take up some regular exercise: you don’t need to go to the gym. Walking, cycling or gardening done regularly can be enough.
• Try to maintain a healthy weight. Eating a balanced diet, which contains plenty of fruit and vegetables, can help with that.
• Avoid drinking excessive amounts of alcohol.

Although making these changes may reduce your risk of developing breast cancer, this does not guarantee that you won’t get ill. But all of the above strategies are good for you anyway, and can make you feel better in many ways.

Breast cancer, when it is found early, can be treated successfully. Unfortunately, the early signs of breast cancer can be hard to detect and are often unclear. You should see your GP if you discover changes like:

• A change to the outline or shape of the breast, lumps or bumpy areas or nipple discharge that is new for you and not milky.
• Feelings of discomfort or pain in one breast that are different from normal (many women say that their breasts are more tender or a bit lumpy just before they have their period).

In most cases, changes to your breast do not mean that you have cancer. But it is worth seeing your doctor. There is no reason for you to feel like you are wasting your doctor’s time if you have discovered a change in your breasts.

Women over 50 years are invited to join the national screening programme and have a mammogram (x-ray of the breasts) once every three years until age 65. This will be extended to women up to 70 years soon. Women over 70 can continue to have regular mammograms by contacting their GP, who will arrange an appointment in a breast screening clinic. Mammography can help to detect breast cancer early, when it is easier to treat.

We have further information on breast screening.