Chemoprevention for increased risk of breast cancer

People who have a family history of breast cancer may consider chemoprevention to reduce their own risk of developing it.

Chemoprevention uses medicine to lower the risk of getting cancer, or the risk of it returning, in healthy people.

Chemoprevention is considered for people who have not developed cancer but have an increased risk of getting the disease due to their family history. 

Breast cancer affects 1 in 7 women in the UK. Some people may have a higher chance of developing breast cancer due to their family history and this is called familial breast cancer. 

Chemoprevention medicines

People with an increased familial breast cancer risk are given 3 medicines called:

Research shows that people who have an increased risk of familial breast cancer can reduce their risk of developing it by taking these medicines for 5 years. 

How these medicines work

Oestrogen is the group of hormones produced by the ovaries. They are important in developing parts of the body, such as growing breasts and starting the menstrual cycle (periods). A large number of breast cancers rely on oestrogen to grow. 

Selective oestrogen receptor modulators (SERMS) can prevent the growth of cancer in people who are diagnosed with oestrogen positive breast cancer by blocking the action of oestrogen. Tamoxifen and raloxifene are SERMS.

Aromatase inhibitors decrease the amount of oestrogen circulating the body by blocking the enzyme that helps make the oestrogen. Anastrozole is an aromatase inhibitor.

Deciding to have chemoprevention

Chemoprevention is for people who have been assessed by a family history or genetics specialist and have a confirmed increased risk of developing breast cancer than in the general population.

Research shows that the greatest benefit is for those who are assessed as high risk.

There is less benefit for people assessed as moderate risk.

People with mutations in the BRCA or PALB2 genes

The benefit of chemoprevention in people with BRCA or PALB2 mutations is uncertain. 

Chemoprevention can reduce the risk of oestrogen positive cancers happening. However, the benefit to people with BRCA and PALB2 gene mutation, who are at increased risk of oestrogen negative cancers, is unclear. 

People with BRCA or PALB2 mutations who have already had breast surgery (with or without reconstruction) to reduce the risk of cancer developing, are not eligible for chemoprevention. 

BRCA carriers should discuss chemoprevention with a breast or genetics clinician. 

Risk-reducing surgery 

The benefit of chemoprevention is significantly less than if you choose to have surgery to reduce your risk of developing breast cancer. This is done by removing as much as possible of the ‘at risk’ breast tissue. This is known as prophylactic (preventative) or risk-reducing surgery. 

Breast screening

If you have been assessed as having an increased familial breast cancer risk (moderate, high or very high) you should continue with breast screening plans, even if you have chosen chemoprevention.

Side effects

Studies suggest that 1 in 5 people will experience side effects which are significant enough to make them stop taking the drugs.

Common side effects include:

  • vaginal dryness
  • hot flushes
  • vaginal discharge
  • nausea (feeling sick)
  • leg cramps

Less common side effects include:

  • increased risk of blood clots
  • strokes (thromboembolism)
  • womb cancer (endometrial cancer)
  • headaches

If you have chemoprevention

If you choose chemoprevention, you should:

  • be monitored regularly
  • have your medicine prescribed by a health professional who is familiar with your personal medical history

This is recommended by the National Institute for Health and Care Excellence (NICE).

For these reasons, we recommend you discuss this with your GP and agree a prescription and follow up plan with them.

Tamoxifen is licensed for the purpose of chemoprevention at a dose of 20mg daily for 5 years, for people at a moderate to high risk of breast cancer. 

Anastrozole and raloxifene are currently not licensed for the purpose of chemoprevention in the UK, but can be prescribed on an unlicensed basis for this purpose. 

The hereditary breast and ovarian cancer service

If needed, we send you an invitation to this clinic and a psychological questionnaire to complete. At your appointment you will be able to ask questions and discuss your management in detail with a team of specialists.

More information

Personalised advice about all of these options is available through the hereditary breast and ovarian cancer service.

More information can be found on the National Institute for Health and Care Excellence (NICE) website. This includes information to help you decide if chemoprevention is right for you. 

If you are from a family that has been assessed as being at moderately increased risk of breast cancer due to the family history, you can seek further advice from your local breast family history clinic.

For women who have been assessed at high risk of breast cancer due to their family history, further advice is available either through your local breast family clinic or the Guy’s cancer genetics service.

For women who carry a BRCA1, BRCA2 or PALB2 mutation, further advice is available through the hereditary breast and ovarian cancer service at Guy's Hospital.

Resource number: 4368/VER2
Date published: March 2023
Review date: March 2026

Contact us

If you have any questions or concerns, please contact your genetics clinician.

Phone: 020 7188 1364  Monday to Friday, 9am to 5pm.

Cancer Genetics Service, Guy’s Regional Genetics Service
Guy’s Hospital
Great Maze Pond
London SE1 9RT

Do you have any comments or concerns about your care?

Contact our Patient Advice and Liaison Service (PALS)

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