Genetic testing for PARP inhibitor treatment in breast cancer

This leaflet is for patients diagnosed with breast cancer, who may be eligible for targeted drug treatment.

Cancer in the general population

Cancer is a common condition. It will affect half of the people in the general population.

For women in the general population:

• the lifetime risk (the chance of getting it at some point in life) of breast cancer is one in eight

For men in the general population:

• the lifetime risk (the chance of getting it at some point in life) of breast cancer is one in 1000

We know that the main thing that increases your risk (risk factor) is increasing age. The older we get the more likely we are to develop cancer, as our bodies become less effective at protecting us. Most cases (90 to 95%) happen by chance. A few (five to 10%) happen when someone has inherited an increased risk of developing cancer.

What is genetic testing?

Genetic testing is a blood test that looks for inherited changes in genes.

What are genes?

Genes contain our DNA. They are like an instruction manual or code that tell our cells how to function.

We have two copies (pairs) of every gene. We inherit one copy from our mother and one copy from our father.

The normal function of a gene is to help protect us from developing cancer. A variant in one copy of a gene causes an increased cancer risk in people who carry it.

If someone has a variant in one copy of a gene, they have a one in two (50%) chance of passing on the variant to each child they have, whatever their gender or the child’s gender.

What is a gene variant?

Sometimes a gene may have a variant (change) that is inherited from one parent or the other. A gene variant stops a gene from working properly.

Are all breast cancers inherited?

Most breast cancers (nine in 10) are caused by a combination of chance and the environment (sporadic). As we get older our bodies are less able to protect us from cell changes. These cell changes can lead to the development of cancer.

Only around one in 10 breast cancers are due to an inherited cause.

What are the genes called?

• BRCA1, BRCA2 and PALB2

  BRCA1, BRCA2 and PALB2 genes help to repair cells in the body. If you have a genetic variant, your cells are less able to be repaired. This would likely explain why you developed breast cancer.

  For women with a variant in the BRCA1 or BRCA2 genes, there is:

  • an up to 70% (just over two thirds) lifetime risk of developing breast cancer

  • an up to 45% (almost half) lifetime risk of developing ovarian cancer

  For women who have already been affected with breast cancer, we know there can be an up to 65% (two thirds) chance of them developing another breast cancer in the future. This can be influenced by the age of her first breast cancer diagnosis. Knowing that someone has a BRCA gene variant may help to direct potential treatment or surgical options.

  Men with a variant in the BRCA2 gene may have:

  • an up to 25% (quarter) lifetime risk of developing prostate cancer

  • about an 8% (less than one in 10) lifetime risk of breast cancer

  Men and women with a BRCA2 gene variant have a small risk (three in 100) of pancreatic cancer.

• PALB2

  For women with a variant in the PALB2 gene there is an up to 55% (just over half) risk of breast cancer. Our knowledge about PALB2 is rapidly increasing, and advice could change over time. We recommend increased breast screening with mammography and / or MRI scans. The PALB2 gene also causes a possible increased risk of pancreatic cancer.

  Specific risk figures and screening advice usually depends on family history. Patients should discuss this further with a genetic clinician.

Are there other cancers linked with BRCA1, BRCA2, or PALB2 genes?

Yes these genes are linked with ovarian, prostate, and pancreatic cancer. It is more likely that we will find a gene variant if you have this pattern of cancers in your family, but not always.

Why have I been referred for genetic testing?

Your Breast Cancer team has referred you for genetic testing to see if you have inherited a gene variant. If you find out you have a gene variant your oncologist will discuss whether to give you targeted treatment.

What is targeted treatment?

BRCA1, BRCA2, or PALB2 genes usually help the body repair damaged cells.

A PARP (poly-ADP ribose polymerase) inhibitor is a targeted cancer treatment that comes as a tablet. PARP is a protein that helps cells repair damage. Cancer cells with a BRCA1, BRCA2, or PALB2 variant already have difficulty repairing themselves. PARP inhibitors block another repair pathway, making it even harder for these cancer cells to survive.

Healthy cells can usually repair themselves in other ways, so they are less affected by the treatment.

If you have a BRCA1, BRCA2, or PALB2 gene variant, your oncologist may offer you treatment with a PARP inhibitor.

Do I have to decide whether to have genetic testing now?

No. You do not need to decide about having genetic testing on the day. You may need more time to think about this and discuss it with your friends and family. A further appointment can be made when you are ready.

If you do decide to go ahead with genetic testing, your specialist nurse will:

• ask you to sign a consent form

• arrange a blood test

What can be done if I decide not to have testing?

Not everyone affected by cancer will choose to have genetic testing. If you decide not to have genetic testing, you and your family members may still be eligible for regular breast screening.

How long will the results take?

Usually the results are available around 6 weeks after testing.

How will I receive my results?

You can choose how you would like to receive your results. This can be via a telephone call or a letter.

What do the results mean?

There are three possible outcomes:

1. A gene variant has been found in one of the genes tested

2. No variants were found in the genes tested

3. A variant of uncertain significance (VUS) has been found in the genes tested

A VUS means that a change has been found in a gene, but we do not yet know if it causes health problems or not.

As scientists learn more, they may find out that the change either:

• increases your chance of developing certain diseases; or

• is harmless and does not affect how the gene works.

If more information becomes available in the future, the meaning of the result may become clearer.

What happens if a gene variant is found?

• Your oncologist will decide if you need PARP inhibitor drug treatment.

• We will refer you to the Clinical Genetics team to discuss your results.

• If a VUS is found we will refer you to the Clinical Genetics team to discuss your results.

Things to think about

Deciding to have diagnostic genetic testing can be a difficult and complex process. You may wish to consider the points below before testing.

• Timing

  Why now? Will it change my immediate treatment? What other challenging events are happening in my life?

• Psychological impact of knowing

  How would I feel if a genetic variant was found? How would I share this information in my family?

• Assess your own coping strategies

  How have I dealt with difficult situations in the past? What strategies do I use to help deal with difficult news?

• Next steps

  If I have a gene variant, what measures might I consider taking to address my risks of breast and ovarian cancer?

There are no right or wrong answers to these questions. Have a think about what your answers may be, so that when you get your result you have an idea of what you might do.

What support is available?

Undergoing diagnostic genetic testing and receiving the results can be a challenging time. Before making a decision or after receiving your results, you may wish to talk through:

• your feelings

• your coping strategies

• other any issues you may have

Several support options are available to breast cancer gene carriers, including the following:

• your genetics clinician

• the Hereditary Breast and Ovarian Clinic (HBOC) Family Service clinic

• BRCA support groups

• clinical psychologist

• your GP

• cancer charities, such as Breast Cancer Care (Someone Like Me service) and Macmillan.

Your genetics clinician will discuss these support options with you in more detail. Between you, you can work out what the best sources of support will be for you.

What is the HBOC Family Service clinic?

We invite BRCA / PALB2 carriers to our HBOC Family Service clinic. At the clinic, you will be able to ask questions and discuss your management in detail with a team of specialists. If we find you have the variant, we will send you:

• an invitation to the clinic

• a leaflet about this service

• a psychological questionnaire to complete 

Can I take part in research studies?

Whatever your result is, there may be a chance for you to take part in a research study. Your nurse specialist can discuss this with you.

Contact details

If you have any questions or concerns, please contact the Breast Cancer Family History team.

• Breast Cancer Family History team, Kent and Canterbury Hospital, Canterbury
  Telephone: 01227 868666
  Email

Useful sources of information

• Breast Cancer Now
  UK-wide charity providing care, information and support to people affected by breast cancer.
  Telephone: 0808 800 6000 (helpline, Monday to Friday 9am to 4pm, Saturday 9am to 1pm)
  Email

• Someone Like Me
  Service provided by Breast Cancer Now. Puts you in touch with a trained volunteer who has (or has had) primary breast cancer, or is undergoing genetic testing, for advice and support.
  Telephone: 0345 077 1893 (helpline, Monday to Thursday, 9am to 5pm, Friday 9am to 4pm)
  Email

• Macmillan Cancer Support
  Support and advice charity for people affected by cancer.
  Telephone: 0808 808 0000 (seven days a week, 8am to 8pm)

[Web sites last accessed 3 September 2026]

This leaflet has been produced with grateful acknowledgement to the Cancer Genetics Service at Guy's Hospital.

We have used the terms 'men' and ‘women’ throughout this leaflet. When we use these terms we also mean people with male or female reproductive organs who do not identify as a man or woman. East Kent Hospitals is committed to supporting people of all gender identities. Please tell your nurse or doctor how you would like them to address you, so we can be sure to get this right.

What do you think of this leaflet?

We welcome feedback, whether positive or negative, as it helps us to improve our care and services.

If you would like to give us feedback about this leaflet, please fill in our short online survey. Either scan the QR code below, or use the web link. We do not record your personal information, unless you provide contact details and would like to talk to us some more.

If you would rather talk to someone instead of filling in a survey, please call the Patient Voice Team.

• Patient Voice Team
  Telephone: 01227 868605
  Email