Homologous recombination deficiency

Find out more about what homologous recombination deficiency (HRD) is and what it could mean for your treatment for ovarian cancer.

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You should be offered testing for homologous recombination deficiency (HRD) if you have recently been diagnosed with stage 3 or stage 4 high-grade epithelial ovarian, fallopian tube or primary peritoneal cancer.

This is as well as being offered a germline test for inherited gene variants.

Watch our video about what HRD means, how you have genetic testing for it and what your HRD status means for treatment options for ovarian cancer.

What's homologous recombination deficiency (HRD)? 

Our DNA is constantly being damaged and repaired. Healthy cells have different ways to repair damaged DNA. One of the body’s repair processes is called homologous recombination. 

Homologous recombination deficiency (HRD) is when cells are unable to repair breaks in their DNA using homologous recombination. This is because the homologous recombination process isn’t working as normal. It means the tumour cells have a harder time repairing damaged DNA.

Genetic testing and hereditary ovarian cancer guide 2025

Genetic testing and hereditary ovarian cancer guide

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Watch our Ask the Experts session about HRD and genetics, led by Dr Alexandra Murray, Consultant Clinical Geneticist and Clinical Director at the University Hospital of Wales.

How is my tumour tested for HRD?

A sample of your tumour is used to test for HRD. A sample can be taken during surgery or through a biopsy. This is a medical procedure to remove a small sample of tumour tissue. 

The tumour sample is sent to your local genetics laboratory. They will send the sample to be looked at under a microscope in a laboratory specialising in HRD testing.

HRD testing looks for both the causes and the effects of HRD. This is because some of its causes are unknown. One of the known causes of HRD is changes to the BRCA1 or BRCA2 genes. A HRD test will look for changes to these genes in the tumour sample. It may also look for changes to other gene variants that cause a change in the homologous recombination repair pathway.

Since some of the causes are unknown, the tumour sample is also tested for the effect of HRD, called genomic instability. This is an increased chance of genetic changes inside cells.

If the tumour cells have either of these changes they are considered HRD positive:

  • changes in the BRCA1 or BRCA2 genes or potentially some other genes 

  • a high amount of genomic instability. 

Speak to your treatment team or clinical genetics team who can explain your result to you. 

What does it mean if my tumour tests positive for HRD?

If your tumour tests positive for HRD, you may have more options of PARP inhibitor drugs as a maintenance treatment. They are more likely to work well too. 

Find out more

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Last reviewed: November 2025

Next review: November 2028

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References

Below is a sample of the references used in our genetic testing and hereditary ovarian cancer information. If you'd like more information about the sources we use, please email us at [email protected]

  • da Cunha Colombo Bonadio, R. R., Fogace, R. N., Miranda, V. C., & Diz, M. (2018) Homologous recombination deficiency in ovarian cancer: a review of its epidemiology and management. Clinics (73, Suppl 1):e450s. Available at DOI: 10.6061/clinics/2018/e450s [Accessed November 2025] 

  • Foo, T, George, A, Banerjee, S. (2021) PARP inhibitors in ovarian cancer: An overview of the practice-changing trials. Genes Chromosomes Cancer, (60)5:385– 397. Available at: 10.1002/gcc.22935 [Accessed November 2025]