Strand of DNA

The cells in our body contain a complete instruction manual that tells them how to make proteins that carry out different functions in the body. This ‘instruction manual’ is the genetic code in our DNA. Each gene is the blueprint for a different protein.

Some proteins help to repair damaged DNA. If the DNA is not repaired, it could multiply out of control and form a tumour.

If one of the genes that creates these repair proteins has a change in it the protein might not work properly. DNA damage might then accumulate and the cell can become cancerous.

One of the ways in which cells repair damaged DNA is called homologous recombination. There are a number of different genes which, if changed, can reduce a cell’s ability to repair itself. This is called homologous recombination deficiency, or HRD.


Watch What is HRD?, an Ovacome webinar with Dr Rowan Miller, Consultant Medical Oncologist specialising in gynae-oncology and early phase clinical trials at University College London and St Bartholomew's Hospitals



BRCA1 and BRCA2 gene changes are both types of HRD.

Changes to the BRCA1 and BRCA2 genes increase the risk of breast cancer and ovarian cancer in women. The lifetime risk of a woman with a BRCA1 gene change developing breast cancer is 60-90%. For ovarian cancer the lifetime risk is 40-60% (rising from the age of 40).

For women with a BRCA2 gene change, the lifetime risk of breast cancer is 45-85% and the risk of ovarian cancer (rising from mid- to late forties) is 10-30%.

BRCA2 gene changes also significantly increase the risk of breast and prostate cancer in men. BRCA1 gene changes are thought to slightly increase a man’s risk of breast cancer, but not to significantly increase their prostate cancer risk. Men are just as likely to carry BRCA gene variations as women, and are just as likely to pass them down to their children so it is important to consider cancer in men in your family tree.

You can find more detailed information about the risks for carriers of these gene changes here.

The Ovarian Cancer Action Hereditary Cancer Risk Tool can be used as a guide to whether you might be eligible for genetic testing based on your own cancer diagnosis and/or family history.

There are other genes involved in homologous recombination. If these genes have changes, they too can cause HRD. These other genes include ATM, ATR, RAD51, and PALB2.


BRCA testing if you have had ovarian cancer

BRCA testing for family members


Last updated July 2023. This page is currently under expert review.