Breast Cancer - Who is at risk?

A number of different factors can affect your risk of developing breast cancer, some of which you can influence by changing your lifestyle and some of which are out of your control. They are:

Family history
Lifetime exposure to oestrogen
Age at which you start a family
Whether you take contraceptive pills
HRT
Diet
How can I reduce my risks?

Family history

Women are considered at increased risk from breast cancer if two or more of their close relatives have had the disease. You need to be particularly vigilant if your mother or sister had the disease before the age of 50. If so, ask your doctor whether you are eligible for more frequent screening.

For some women their predisposition will be due to carrying the two breast cancer genes - BRCA1 and BRCA2 - that have recently been identified. A woman carrying either of these genes is thought to have about an 80 per cent risk of developing breast cancer at some time in her life. Both are large genes, with possible different mutations, making it particularly difficult to develop accurate routine screening tests.

Other women are likely to carry genes that predispose them to breast cancer but are yet to be identified. But before you start dredging up your family tree remember that 90 per cent of breast cancers have nothing to do with family history.

Some women with a family history of breast cancer are taking the drug tamoxifen to reduce their chance of developing the disease. Tamoxifen works by blocking the effects of the female hormone oestrogen which is known to stimulate breast tissue to grow.

It's well known that women with cancer in one breast can reduce their risk of developing cancer in the other breast by 40 per cent simply by taking tamoxifen.

Lifetime exposure to oestrogen

The amount of the female hormone oestrogen you are exposed to over the course of a lifetime influences your risk of developing breast cancer.

The reason is that the speed at which breast cells divide is directly related to oestrogen levels in the body, and the more frequently a cell divides the greater the chance it has of turning into cancer.

An important factor influencing your overall exposure to oestrogen is the number of menstrual cycles you experience, since each cycle exposes you to more hormone. Starting your periods late, having an early menopause, having children and breast feeding will all combine to reduce your total number of periods and protect you from breast cancer.

Age at which you start a family

Childless women, or those who have their first child after the age of 30, have double the risk of developing breast cancer than women who have a child before they reach 20.

The reason is that breast cells don't completely mature until they are exposed to hormones released during the late stages of pregnancy. Once breast cells have fully developed they are thought to be less vulnerable to chemicals and other agents that damage DNA.

Whether you take contraceptive pills

Recent research suggests there is a small increase in the risk of developing breast cancer when you take the combined oral contraceptive pill - both during this time and for the following 10 years. The excess risk, however, disappears 10 years or more after the end of pill use.

HRT

For the first 10 years, the health benefits of hormone replacement therapy (such as reduced osteoporosis and heart disease) are thought to outweigh the risks.

However, some studies have shown that the risk of breast cancer increases after 10 years of taking hormone replacement therapy (HRT).

For this reason HRT is usually only given to a woman with a strong family history of breast cancer if she is experiencing major problems with the menopause.

Diet

Breast cancer rates are known to be four to seven times higher in the US than Japan. One reason is thought to be that Japanese diets are rich in sources of plant oestrogens, known as phytooestrogens.

Phytooestorgens may slow the growth of breast cells by blocking the effects of normal oestrogen. Some studies show that consumption of phytooestrogens is associated with lower rates of breast cancer and less severe menopause symptoms.

Phytooestrogens are found in a variety of fruits and vegetables, including soya bean and linseed products, apples, alfalfa sprouts, split peas and spinach.

Drinking large quantities of alcohol can increase your risk of developing breast cancer, since alcohol blocks enzymes that breakdown oestrogen. The result is higher-than-normal levels of oestrogen.

One area of controversy is the relationship between dietary fat intake and risk of developing breast cancer. For years researchers thought that reducing fat consumption helped protect against breast cancer.

More recent studies have found that the risks are the same for those on high fat and low fat diets. It's now thought that in Asian and African countries, where low fat diets are the norm, the low incidence of breast cancer has more to do with the fact that women from these countries tend to be extremely lean and active.

How can I reduce my risks?

There are a number of steps you can start taking now to reduce your risk of breast cancer:

• Try to exercise a few times a week
• Maintain a healthy body weight for your age and height
• Try to eat a wide variety of fresh fruit and vegetables and increase the amount of fibre in your diet
• Limit the amount of alcohol you drink, ideally to no more than two drinks a day