All About Breast Cancer ( 1-Hereditary Factors )

Breast Cancer - Hereditary Factors

 

Most cases of breast cancer occur 'by chance'. However, breast cancer does occur more often than usual in some families because of their genetic make-up. If you are concerned that your risk of developing breast cancer is higher than usual because of your family history, then see your doctor for assessment. If you have a moderately increased risk then an option is to have breast screening (mammography) at an earlier age than normal, and more often than usual. If you have a high risk then you may be offered genetic testing, counselling and regular breast screening tests.

Some facts about breast cancer

• Breast cancer is one of the most common cancers in the world.
• In the UK about 1 in 9 women develop breast cancer at some stage of their life.
• The biggest 'risk factor' for developing breast cancer is increasing age. Most cases develop in women over the age of 50.
• Of women who do develop breast cancer, most do not have a strong 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 test of the breast) 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.

There are three 'faulty' genes that have been identified which are particularly associated with breast cancer. These are 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.

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'.

Note: not all women with these faulty genes will develop breast cancer. It is just that the risk is increased.

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 with 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 40.
• 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.
• If you come from certain ethnic backgrounds. For example, the Ashkenazi Jewish community have a higher incidence of genes which increase the risk.

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.

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 guidelines which doctors can refer to when assessing the risk of breast cancer for individual women.

If your risk is assessed as normal or near-normal

Most women have a normal or near-normal risk of developing breast cancer. (That is about a 1 in 9 chance of developing breast cancer - most commonly after the age of 50.) If your risk is normal or near-normal you should still consider the 'usual' advice to women. That is:

• Be 'breast aware'. Get to know how your breasts normally look and feel, and report any changes promptly to a doctor.
• Go for routine breast screening. All women in the UK aged between 50 and 70 are invited to have a routine mammography every three years. Mammography is an X-ray test that aims to detect breast cancer at an early stage when treatment is most likely to be curative.
• Consider altering other factors which may affect your risk of breast cancer:
  • If you are past the menopause and are overweight or obese, losing some weight will reduce your risk.
  • Regular exercise reduces the risk.
  • If you drink a lot of alcohol the risk is increased. Cutting back to sensible drinking is best if this applies to you.
  • There is a slightly increased risk of developing breast cancer if you take the combined oral contraceptive pill (COCP) when you are over 35 years or hormone replacement therapy (HRT). If you use these you may wish to consider other options.
  • If you have children, women who breast-feed have a reduced risk of developing breast cancer compared with those who bottle-feed.
• See your GP if there is a change in your family history. For example, if a close family member develops cancer of the breast or ovary after your risk of breast cancer has previously been assessed. This may mean that your risk has changed.

If your risk is assessed as moderate or high

You will be offered a referral to see a specialist. He or she will make a detailed assessment of your risk on the basis of family history.

Note: postmenopausal woman with a moderate-to-high risk of breast cancer should not take HRT. However, you can still take HRT until you reach 50 years of age; for example, if you go through the menopause early and need hormone replacement.

If your risk is confirmed as moderately high

You are likely to be offered mammography screening to commence at the age of 40 (rather than the usual age of 50). Also, mammography is likely to be every year rather than the usual three-yearly.

If your risk is high

You are likely to be offered genetic testing and counselling. This is usually done in a specialist genetics clinic. This may involve tests to see if you carry one or more of the faulty genes mentioned above. A blood test may also be taken from your family member who has breast cancer. Depending on the outcome of the tests and assessment of the risk, some women are offered regular mammography screening from an early age.

If you are aged 30-49 years and have BRCA1 or BRCA2 genes, or are over 20 years and have TP53 gene then you may be offered yearly MRI and mammograms. An MRI scan may be a more sensitive test than mammograms for younger women. When mammography is recommended in women younger than 50 years of age, digital mammography may be used in preference to conventional mammography. Digital mammography takes an electronic picture of your breast and stores it directly in a computer. Digital mammography uses less radiation than film mammography.

For a very small number of women, whose risk is very high, surgery to remove the breasts and/or ovaries before cancer develops may be an option. This is not an option which is taken lightly and is only done after full risk assessment and counselling.

Other faulty genes are being identified that result in an increased risk of breast cancer. Testing for these is not offered currently, but may be available in the next few years.

Further help and information

Breast Cancer Care

Kiln House, 210 New King Road, London, SW6 4NZ
Helpline: 0808 800 6000
Web: www.breastcancercare.org.uk
The leading provider of breast cancer information and support across the UK.

National Hereditary Breast Cancer Helpline

Tel: 01629 813000
Web: www.breastcancergenetics.co.uk
Supplies information to women concerned about their risk of breast cancer because of family history.

OPERA

This is a personalised online risk assessment tool to predict likelihood of having genetic risk for breast and/or ovarian cancer.
Web: www.macmillan.org.uk/Cancerinformation/Causesriskfactors/Genetics/OPERA.aspx

Cancer Research UK

Web: www.cancerhelp.org.uk provides facts about cancer including treatment choices.

Macmillan Cancer Support

Tel: 0808 800 1234
Web: www.macmillan.org.uk
They provide information and support to anyone affected by cancer.

References

• Breast cancer - managing family history, Clinical Knowledge Summaries (November 2009)
• Familial breast cancer, NICE Clinical Guideline (October 2006); the classification and care of women at risk of familial breast cancer in primary, secondary and tertiary care
• Leach MO, Boggis CR, Dixon AK, et al; Screening with magnetic resonance imaging and mammography of a UK population at high familial risk of breast cancer: a prospective multicentre cohort study (MARIBS). Lancet. 2005 May 21-27;365(9473):1769-78. [abstract]
• Rebbeck TR, Friebel T, Lynch HT, et al; Bilateral prophylactic mastectomy reduces breast cancer risk in BRCA1 and BRCA2 mutation carriers: the PROSE Study Group. J Clin Oncol. 2004 Mar 15;22(6):1055-62. Epub 2004 Feb 23. [abstract]
• Robson M, Offit K; Clinical practice. Management of an inherited predisposition to breast cancer. N Engl J Med. 2007 Jul 12;357(2):154-62.
• Sivell S, Iredale R, Gray J, et al; Cancer genetic risk assessment for individuals at risk of familial breast cancer. Cochrane Database Syst Rev. 2007 Apr 18;(2):CD003721. [abstract]