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Cancer treatment

PARP inhibitor maintenance treatment for ovarian cancer

PARP inhibitors are tablets taken after chemotherapy to keep ovarian cancer under control for longer. They work by blocking a repair protein that cancer cells with faulty DNA repair depend on. Eligibility depends on cancer type, response to chemotherapy and genetic testing, and the prescribing is done by a specialist team.

Last checked: 2026-10-03

Key facts

At a glance.

  • What they are

    Oral targeted medicines. The NHS genomics service lists three in use: olaparib, rucaparib and niraparib.

  • Mechanism

    They block PARP, a repair protein. Cells that already lack homologous recombination repair, such as many with BRCA changes, cannot cope and die.

  • Maintenance

    Given after a good response to platinum chemotherapy, to delay the return of the cancer, not to replace chemotherapy.

  • Testing first

    Tumour testing for homologous recombination deficiency and BRCA status helps decide the drug.

  • Side effects

    Tiredness, nausea and blood count changes are among the commonest, and need regular blood tests.

How PARP inhibitors work

Cells repair damage to their DNA all the time. PARP is a protein that helps fix single-strand breaks. NHS England genomics teaching explains that blocking PARP causes breaks to build up and, during cell division, become double-strand breaks. Healthy cells repair these by homologous recombination, but cells lacking that pathway cannot.

Cells with changes in BRCA1, BRCA2 or other repair genes are called homologous recombination deficient (HRD). This concept, called synthetic lethality, explains why the drugs can be selective: a fault in one pathway is tolerated, but faults in two together are fatal for the cell.

Who is considered

Cancer Research UK describes PARP inhibitors as options for people with high-grade epithelial ovarian cancer that has responded well to platinum chemotherapy, at stage 3 or 4 or after relapse. Olaparib requires a BRCA1 or BRCA2 change, while niraparib and rucaparib may be available without one.

NHS England genomics material states that PARP inhibitors are now approved for all patients as first-line maintenance for ovarian cancer regardless of BRCA status. Because licensing and commissioning evolve, your oncologist is the reliable source on which drug applies at the time of your treatment, and NICE guidance underpins what the NHS offers.

The tests behind the decision

Cancer Research UK states that specialists test the cancer cells for homologous recombination deficiency, checking for BRCA1 and BRCA2 changes and for genomic instability. Macmillan stresses that HRD testing checks the cancer only and is not a test for inherited gene changes.

A blood test for inherited BRCA variants is a separate step, usually offered through genetics services. A germline result matters for relatives, who may then be offered testing and risk-reducing options.

Taking the tablets

PARP inhibitors are tablets or capsules that you swallow. They are taken at home, following the schedule that the specialist team gives, with regular hospital checks. The dose and any time limit depend on the medicine and on how well it is tolerated, and are not something to adjust yourself.

Because they are maintenance treatments, they continue for as long as they are helping and the side effects are manageable. Bevacizumab, a drip-given targeted medicine, can be used instead of or sometimes alongside, for stage 3 or 4 high-grade disease, according to Cancer Research UK.

Side effects and monitoring

The NHS genomics page lists increased risk of infection, anaemia, bleeding, tiredness, nausea, vomiting, mouth soreness, diarrhoea, headache, dizziness and altered liver or kidney function. Blood tests are used to watch the blood count, and the dose may be paused or lowered if counts fall.

Contact the oncology team promptly about fever, bleeding, bruising, severe vomiting or breathlessness, using the number on your treatment card. For emergencies out of hours, use NHS 111 or A&E as advised by the team. Some people have enduring changes in blood counts that need specialist review.

Frequently asked

Questions people ask.

Quick, plain-English answers to the questions we hear most.

  • Is a PARP inhibitor a form of chemotherapy?

    It is classed as a targeted treatment. It acts on a specific repair pathway instead of broadly attacking dividing cells, and it is taken by mouth.

  • Do I need a BRCA change to have one?

    Not always. NHS England genomics teaching says approval covers first-line maintenance regardless of BRCA status, but the particular drug may depend on BRCA and HRD results.

  • What is HRD?

    Homologous recombination deficiency means the cancer cells are poor at one kind of DNA repair. HRD testing is done on tumour tissue, not on blood.

  • How long do people take them?

    Treatment continues while it is working and tolerated, according to the plan agreed with your oncologist, which can differ between drugs.

  • Will blood tests be needed?

    Yes. Blood counts and liver and kidney function are monitored, because PARP inhibitors can cause anaemia and other changes.

  • Can I take them if my cancer comes back?

    Some people have them for relapsed disease, according to Cancer Research UK. Eligibility depends on earlier treatment, response and genetic results.

  • Are they used for other cancers?

    Yes. The NHS genomics page lists use in some breast and prostate cancers with BRCA or related repair gene changes.

  • What if I feel unwell on treatment?

    Tell your team promptly. Cancer Research UK advises reporting any problems or side effects, and nurses give contact numbers for home.

  • Does a good response to chemotherapy matter?

    Yes. PARP inhibitor maintenance is aimed at people whose cancer has responded well to platinum chemotherapy, because those cancers are most likely to depend on faulty repair.

Where this comes from

Sources and checking.

This guide is for information, not medical advice.

Your GP or consultant knows your history and can tell you which parts apply to you. If your symptoms are severe, rapidly worsening, or come with red-flag features, seek urgent medical care. Figures and availability change, so treat them as a guide and confirm with the provider.

Published 2026-10-03, next review 2027-10-03.

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