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Causes & 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.

Reduce Beast Cancer risk - SingHealth-Duke NUS Breast Cancer

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.

Usage of oral contraceptive pills and combined hormonal replacement therapy is a modifiable risk factor for 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.

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