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Breast Cancer

Breast Cancer - How to prevent?

Breast Cancer - Causes and Risk Factors

The causes of breast cancer are not exactly known but there are risk factors that increase the chance of developing breast cancer. Having risk factors do not mean a woman will definitely develop breast cancer, as many women who have had breast cancer did not have any apparent risk factors.

Some risk factors such as gender and age, or those related to our environment cannot be changed (non-modifiable), while others are modifiable as they are related to our lifestyle choices.

Non-modifiable Risk Factors

  • Age and gender
  • Early menarche, late menopause
  • Family history and genetic factors
  • Previous breast cancer
  • Certain breast changes in biopsies (such as atypical ductal hyperplasia and LCIS)
  • Radiation exposure for medical reasons

Being a woman is a risk factor for developing breast cancer. Women have a much higher chance of developing breast cancer than men due to the female hormones oestrogen and progesterone.

This risk is increased with longer hormonal exposure in women with early menarche (onset of menstruation) before the age of 12 and late menopause (after the age of 55).

Other hormonal-related factors include never having children, late childbearing (after the age of 30), and obesity, especially excessive weight gain in post-menopausal women. This risk also increases with age.

Genetic factors and family history of breast cancer, especially in a first-degree relative (mother, sister or daughter), or two or more close relatives such as cousins and the presence of genetic alterations in certain genes such as BRCA1 and BRCA2 which are associated with significant lifetime risks of breast cancer.

A past history of breast cancer, radiation exposure for medical reasons and certain benign conditions such as atypical ductal hyperplasia, atypical lobular hyperplasia or lobular carcinoma in-situ diagnosed on breast biopsy also increase the risk.

Modifiable Risk Factors

  • Lack of exercise
  • Excessive alcohol consumption over a long period of time
  • Smoking
  • Use of oral contraceptive pills (OCP) and combined hormonal replacement therapy (HRT) over a long period of time

However, most women who have breast cancer have none of the above risk factors. Likewise, not possessing any of these risk factors does not mean that one will not get breast cancer. There is ongoing research to learn more about these factors, as well as ways to prevent breast cancer.

Reducing the Risk of Breast Cancer

There is no sure way to prevent breast cancer, but the risks can be lowered. These include modifying the risk factors which we have control over such as:

  • Exercise and increasing physical activity
  • Limiting alcohol intake
  • Keeping a healthy diet to prevent obesity, especially post-menopause
  • Cease smoking. Smoking increases the risk of many other cancers and is bad for overall health. There are suggestions of links between smoking and breast cancer
  • Have more children if one is able to
  • Breastfeeding is also protective
  • Limit the use of HRT and OCP
  • Limit your exposure to environmental pollution and radiation such as the use of medical imaging like computerised tomography (CT) scans unless really necessary

In high-risk women, such as those with a very strong family history or have genetic mutations such as the BRCA, risk-reducing options include taking drugs or having surgery that can reduce their risk. Risk-reducing surgeries include removal of the breast (mastectomy) and removal of the ovaries.

An alternative management strategy to risk-reduction methods is close surveillance. While this does not reduce the risk of cancer development, it does improve outcome by discovering the cancers in earlier stages, allowing earlier treatment and hence better outcomes.

Genetic Risk Assessment for Hereditary Breast Cancer & Implications

What is Hereditary Breast and Ovarian Cancer (HBOC) syndrome?

About 5 to 10 percent of breast cancers can be attributed to hereditary breast and ovarian cancer (HBOC) syndrome. Genetic change (mutation) in the BRCA1 or BRCA2 gene is the most common cause of Hereditary Breast and Ovarian Cancer (HBOC).

Individuals with BRCA1 or BRCA2 mutation tend to develop cancer at an earlier age than the general population and have higher risk for bilateral breast cancer, a second primary tumour in a different tissue, and cancer recurrence.

Mutations in other less common genes have also been found to increase the risk of developing breast and other cancers.

Who might be at risk?

Hereditary Breast and Ovarian Cancer (HBOC) is an adult-onset, cancer predisposition syndrome which can be passed down through generations.

The history of cancer in your close relatives is a clue about the chance of HBOC syndrome in your family. It is more likely if one or more of the following features can be confirmed in your family:

  • Young age of onset
  • Bilateral breast cancer or personal history of multiple cancers
  • Family history of ovarian, peritoneal, fallopian tube, pancreatic cancers and/or melanoma
  • History of male breast cancer in the family

How is Hereditary Breast and Ovarian Cancer (HBOC) syndrome diagnosed?

Genetic testing for Hereditary Breast and Ovarian Cancer (HBOC) syndrome is a blood test that is available at the Cancer Genetics Service at NCCS when specific criteria are met. Genetic testing is complex, thus it does not take place without genetic counselling and the process of informed consent.

What does genetic counselling involve?

Cancer genetic counselling is a process to assess a person's risk of having an inherited susceptibility to cancer. It is usually provided by a genetic counsellor and/or cancer geneticist to help people understand and adapt to the medical, psychological and familial implications of genetic contributions to cancer.

Genetic counselling can help you better understand the outcomes and impacts of genetic testing and the possible implications when finding a genetic mutation of Hereditary Breast and Ovarian Cancer (HBOC) syndrome.

What can I do to reduce my risk of developing breast or ovarian cancer if I have a BRCA gene mutation?

Increased surveillance (clinical breast exam, mammogram and MRI) and consideration of risk-reducing interventions (such as chemoprevention and preventive mastectomy or oophorectomy) are recommended.

What should I do if I am concerned?

If your family history of cancer suggests Hereditary Breast and Ovarian Cancer (HBOC) syndrome, please talk to your doctor regarding your concerns and they will make the necessary arrangements if a genetic risk assessment is needed.


Finding a genetic mutation of Hereditary Breast and Ovarian Cancer (HBOC) syndrome may help to:

  • Inform family members about their own cancer risk
  • Direct appropriate cancer screening and risk-reduction options for affected patients and family, and avoid unnecessary testing in those who do not require increased surveillance
  • Explain the history of cancer in a family

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