乳腺癌遺傳因素-Breast Cancer-Hereditary Factors

Some facts about breast cancer

• In the UK about 1 in 9 women develop breast cancer before the age of 85.
• Most women (8 in 9 women) do not develop breast cancer before the age of 85.
• The biggest 'risk factor' for developing breast cancer is increasing age. About 4 in 5 cases first develop in women over the age of 50.
• Of women who do develop breast cancer, most do not have a family history of the disease. However, some women do come from families where breast cancer occurs more often than usual (see below).
• If breast cancer is detected in an early stage, there is a good chance of a cure. Mammography (x-ray of the breast) is a test that can detect breast cancer at an early stage.

Breast cancer, genes and family history

The cause of breast cancer is probably a combination of factors. These include lifestyle factors, environmental factors, hormone factors, and probably other unknown factors. Your genetic make-up is another factor which is known to be involved.

Several 'faulty' genes have been identified which are particularly associated breast cancer. These include the BRCA1 gene, the BRCA2 gene, and the TP53 gene. If you carry one or more of these genes you have an increased risk of developing breast cancer (and certain other cancers such as ovarian cancer). Also, the cancer tends to develop at an earlier age than usual. These faulty genes are just the main ones so far identified which are related to breast cancer. There are probably others which cause a smaller increased risk which have not yet been identified. Note: not all women with these faulty genes will develop breast cancer. It is just that the risk is increased.

About 1 in 20 women are likely to carry a faulty gene that gives them a higher risk than the general population of developing breast cancer. This may vary from a moderate increase in risk to a high risk. You inherit half of your genes from your mother and half of your genes from your father. So, if you carry a faulty gene there is a 50:50 chance that you will pass it on to each child that you have. Because of these faulty genes, breast cancer does occur more often than usual in some families. This is sometimes called 'familial breast cancer' or 'hereditary breast cancer'.

Assessing your risk

As breast cancer is common, many of us will have a relative who has been diagnosed with breast cancer. This is not usually due to any of the 'faulty genes' mentioned above, but is more often 'by chance'. Most women with a family history of breast cancer do not have a greatly increased risk of developing breast cancer compared to the normal risk of the general population. However, some women are at greater risk than usual.

In general, your risk becomes greater:

• The more blood relatives you have who have been diagnosed with breast cancer.
• The closer the blood relationship to you of the person with breast cancer.
• The younger your relatives were when they were first diagnosed with breast cancer. Especially if they were under the age of 50.
• If a relative had breast cancer which affected both breasts.
• If a male relative developed breast cancer.
• If both breast and ovarian cancer run in the family.
• If certain other uncommon cancers have developed in family members. For example: ovarian cancer, a sarcoma under the age of 45, a glioma, or childhood adrenal cancer. 醫(yī)學(xué)全在線www.med126.com
• If you come from certain ethnic backgrounds. For example, the Ashkenazi jewish community have a higher incidence of genes which increase the risk of breast cancer.

What should I do if I am concerned?

If you are concerned about a history of breast cancer in your family you should see your GP. He or she will want to take a family history. Therefore, before seeing your GP, try to get as much detail about who in your family has been diagnosed with breast cancer (or other cancers), at what age they were diagnosed, and their exact blood relationship to you.

Your GP will wish to know any relevant details about first and second degree relatives (from your father's side as well as from your mother's side).

• First degree relatives are - mother, father, daughters, sons, sisters, or brothers.
• Second degree relatives are - grandparents, grandchildren, aunts, uncles, nieces, nephews, half-sisters and half-brothers.

On the basis of the family history, it is usually possible for your GP to assess your risk as either near normal, moderate, or high. If your risk is moderate or high then, if you wish, you may be referred to a specialist for further assessment and counselling. If you are under the age of 40, referral may not be appropriate until you are 40 if your increased risk is not very high.

For details of the factors used to assess the risk, see the website of the National Institute of Clinical Excellence (details at the end of the leaflet). They have produced national guidelines which doctors can refer to when assessing the risk of breast cancer for individual women.

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