Study: Some people with recurrent ovarian cancer have long-lasting benefit from PARP inhibitors

RELEVANCE

Most relevant for: People with platinum-sensitive recurrent ovarian cancer who have had a long response to PARP inhibitor maintenance therapy.

It may also be relevant for:

• people with ovarian cancer
• people with platinum-sensitive ovarian cancer

Relevance: Medium

Strength of Science: Medium-High

Research Timeline: Post Approval

More rating details

What is this study about?

This study looked at people with platinum-sensitive recurrent ovarian cancer who had an exceptional response to maintenance treatment with a PARP inhibitor. Platinum sensitive means that the cancer responded to platinum chemotherapy and did not come back right away after that treatment. Maintenance therapy is treatment given after chemotherapy to help keep cancer from growing or coming back. You can find out more about maintenance therapy for ovarian cancer here.

Researchers defined an exceptional response as living without cancer worsening or coming back for at least 5 years after starting a PARP inhibitor. The study included 320 people from 41 sites in 14 countries. Participants were followed for almost 7 years. Most people were on a PARP inhibitor for somewhat longer than 6 years.

Why is this study important?

PARP inhibitors can help delay ovarian cancer from coming back or getting worse for some people, especially those whose cancers are linked to BRCA1, BRCA2, or other DNA repair genes. However, these medicines can cause side effects, and some cancers can become resistant to PARP inhibitors.

The results of this study only apply to people with recurrent platinum-sensitive ovarian cancer. For people with recurrent ovarian cancer receiving a PARP inhibitor, the ideal time to stop a PARP inhibitor is not well defined.

In the recurrent setting, treatment recommendations often suggest staying on a PARP inhibitor until the cancer gets worse or the side effects become too difficult to manage. This study provides helpful information about people who have already done well for many years. However, more research is needed to understand how long to continue treatment, who can safely stop treatment, and when and what long-term risks may occur.

Study findings

320 people who had an exceptional response to PARP inhibitors were included in the study. Among these:

• 107 had an inherited BRCA1 mutation
• 100 had an inherited BRCA2 mutation
• 11 had a tumor mutation in BRCA1
• 15 had a tumor mutation in BRCA2
• 40 did not have an inherited or tumor mutation in BRCA1 or BRCA2
• For 47 participants, it was not known whether they had a BRCA1 or BRCA2 mutation

 Long-term outcomes remained favorable for almost all participants.

• At 7.5 years, the cancer did not return or worsen for almost 90% of participants.
• At 10 years, the cancer did not return or worsen for almost 80% of participants.

Of the 320 participants, 85 (about 27%) stopped taking PARP inhibitors for reasons other than their cancer getting worse. Among these 85 people, 90% had an estimated 10 years before their cancer came back.

This finding suggests that some people with an exceptional response to PARP inhibitors may not need to stay on these drugs forever, but the study was not designed to determine when treatment can be stopped safely. While this finding is reassuring, people should not stop treatment without talking with their healthcare team.

Long-term safety

Researchers also looked closely at long-term safety. Five people (1.6%) in the study developed serious, late-onset blood cancers, such as myelodysplastic syndrome (MDS) or acute myeloid leukemia (AML). These are rare but serious blood cancers that have been reported after PARP inhibitor treatment and chemotherapy. Since all the people in the study also received chemotherapy, it cannot be determined if the PARP inhibitor, the chemotherapy or a combination of both led to these rare cancers.

People who currently take or previously took PARP inhibitors should continue to receive blood tests and should report unusual fatigue, infections and easy bruising or bleeding to their care team.

PARP inhibitor side effects

As with any cancer treatment, PARP inhibitors can cause unpleasant side effects, including:

• abdominal (belly) pain
• bleeding problems
• diarrhea and constipation
• dizziness
• fatigue
• headaches
• infections
• nausea and vomiting
• sense of taste changes
• unexplained weight loss

What does this mean for me?

These findings do not apply to people who received a PARP inhibitor as their first-line therapy or “up-front”. Nowadays, most people will not receive a PARP inhibitor in the recurrent setting because they have already been treated with one up front.

If you have platinum-sensitive recurrent ovarian cancer, have received a PARP inhibitor as maintenance therapy, and have had a long-lasting response, findings from this study may be reassuring. Many people in this study who had already gone 5 years without cancer growth continued to do well for years afterward.

This study does not mean everyone should stop taking a PARP inhibitor after a certain number of years. It is important to discuss the ideal length of PARP inhibitor treatment with your oncologist, especially if you have been on treatment for a long time, are having side effects, or are concerned about long-term risks.

People taking PARP inhibitors should:

• keep regular oncology visits
• ask how often you need scans, blood counts and other monitoring
• report new or worsening side effects promptly

Importantly, do not stop, pause or change your PARP inhibitor dose without discussing it with your healthcare team.

If your cancer has not come back or worsened for many years, your doctor may talk with you about whether continuing treatment, lowering the dose or stopping treatment is reasonable for your situation. The right decision may depend on your cancer history, genetic testing, prior treatments, side effects, blood counts, personal preferences, and how comfortable you are with uncertainty.

Reference:

Haggstrom L, Lee YC, Barretina-Ginesta MP, et al. Long-Term Outcomes in Patients With Recurrent Ovarian Cancer and Exceptional Response to PARP Inhibitors. JAMA Oncology. Published online June 25, 2026. doi:10.1001/jamaoncol.2026.1924.

Disclosure: Disclosure: FORCE receives funding from industry sponsors, including companies that manufacture cancer drugs, tests and devices. All XRAYS articles are written independently of any sponsor and are reviewed by members of our Scientific Advisory Board prior to publication to assure scientific integrity. 

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posted 09/19/2026