Key messages
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Compared to an inactive 'dummy' medication (placebo), medications called PARPi (poly (ADP-ribose) polymerase inhibitors) given as a daily tablet for maintenance treatment (to prevent/delay cancer coming back) after chemotherapy:
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may increase length of life (survival) of women with advanced cancer of the ovaries (epithelial ovarian cancer (EOC)) and lead to a longer time until disease regrowth (progression/recurrence) after treatment for newly-diagnosed ovarian cancer;
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probably slightly increase survival after ovarian cancer regrows, and lead to a longer time before further disease regrowth in women with EOC that has come back more than six months after previous treatment (known as 'recurrent platinum-sensitive EOC');
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probably cause a large increase in the risk of severe side effects; and
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may reduce quality of life, although this is probably too slight to be noticeable.
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Treatment with PARPi instead of further chemotherapy after the regrowth of ovarian cancer does not increase survival time and may not affect the time to further regrowth.
What is epithelial ovarian cancer?
EOC is cancer that arises from the female reproductive system, specifically, the surface layer of ovaries, fallopian tubes, and tummy (abdominal) cavity (peritoneum). EOC is often diagnosed at a late (advanced) stage when disease has spread within the tummy cavity. Initial treatment is a combination of surgery and chemotherapy. Advanced EOC very often recurs and further treatment is required. Scientists have been looking at new ways to stop cancer cells regrowing.
What are PARP inhibitors?
Being able to repair DNA is vital to the survival of the cells of the human body. Normal cells have more than one pathway to repair DNA. However, cancer cells often have defects in DNA repair pathways. The BRCA gene is involved in DNA repair and is commonly damaged (mutated) in the tumours of people with EOC. Blocking another DNA repair pathway with a PARPi stops cancer cells from repairing DNA, causing cells to die. PARPi therefore differ from conventional chemotherapy, and may work better in BRCA-mutated cells.
What did we want to find out?
We wanted to find out if PARPi treatment, given with chemotherapy or given after chemotherapy as maintenance treatment:
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delays death;
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delays the disease coming back or getting worse;
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improves quality of life;
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has unwanted side effects.
What did we do?
We searched for studies called 'randomised controlled trials' that used PARPi in women with newly-diagnosed EOC and in those whose cancer had returned, either more than six months after stopping platinum-based chemotherapy (platinum-sensitive recurrence) or within six months of platinum-based chemotherapy (platinum-resistant recurrence). We summarised the studies' results and rated our confidence in the evidence.
What did we find?
We found 24 studies of PARPi that involved 8961 participants. Eight studies included women with newly-diagnosed EOC ('first-line treatment') and 16 included women with recurrent cancer. We also found six ongoing studies.
First-line treatment
PARPi maintenance treatment after chemotherapy for women with newly diagnosed ovarian cancer:
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may slightly increase how long women survived overall, despite a long delay until recurrence (survival at 5 years 50% with PARPI versus 42% with placebo), although this is complicated by subsequent treatments;
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leads to a much longer delay until the recurrence of cancer (no progression of the disease at 12 months: 48% with PARPi versus 24% for placebo);
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but there is a big increase in the risk of severe side effects with PARPi, and PARPi may slightly worsen quality of life.
Treatment of platinum-sensitive recurrent EOC
PARPi maintenance treatment after chemotherapy for platinum-sensitive ovarian cancer:
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probably slightly increases overall survival time after treatment (alive at 48 months 44% with PARPi versus 38% for placebo);
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leads to a much longer delay until recurrence of cancer (no progression of the disease at 12 months: 37% with PARPi versus 6% for placebo);
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but probably causes a large increase in the risk of severe side effects, though probably no difference in quality of life.
Compared to chemotherapy treatment, PARPi:
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may make little to no difference to overall survival time but may increase the risk of serious side effects;
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we are very uncertain about its effect on progression of cancer and quality of life.
Many of these studies only included patients with BRCA mutations.
Treatment of platinum-resistant recurrent EOC
Compared to chemotherapy treatment, PARPi:
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reduces overall survival time but may have little to no effect on how long it takes until the cancer progresses or the risk of severe side effects.
What limited our confidence in the evidence?
In general, we have confidence in the way most of the studies were carried out. However, people knew which treatment they were getting in some studies and some studies involved only a small number of people. These factors could have influenced the results. There was not enough information about quality of life (that is, how well people feel when they are on treatment), and different methods were used to measure it, which limited our ability to combine results.
How up to date is this review?
The evidence is current to December 2025.
Read the full abstract
Background
Ovarian cancer is the sixth most common cancer in women world-wide. Epithelial ovarian cancer (EOC) is the most common; three-quarters of women present when disease has spread outside the pelvis (stage III or IV). Treatment consists of a combination of surgery and platinum-based chemotherapy. Although initial responses to chemotherapy are good, most women with advanced disease will relapse.
PARP (poly (ADP-ribose) polymerase) inhibitors (PARPi), are a type of anticancer treatment that works by preventing cancer cells from repairing DNA damage, especially in those with breast cancer susceptibility gene (BRCA) variants. PARPi offer a different mechanism of anticancer treatment from conventional chemotherapy.
Objectives
To assess the benefits and harms of poly (ADP-ribose) polymerase inhibitors (PARPi) versus placebo or other anti-cancer treatments for women with newly diagnosed or recurrent epithelial ovarian cancer (EOC).
Search strategy
We identified randomised controlled trials (RCTs) by searching the Cochrane Central Register of Controlled Trials MEDLINE, and Embase up to 2 December 2025.
Selection criteria
We included trials that randomised women with EOC to PARPi with no treatment, or PARPi versus conventional chemotherapy, or PARPi together with conventional chemotherapy versus conventional chemotherapy alone.
Data collection and analysis
We used standard Cochrane methodology. Two review authors independently assessed whether studies met the inclusion criteria. We contacted investigators for additional data. Outcomes included overall survival (OS), objective response rate (ORR), quality of life (QoL) and rate of adverse events.
Main results
We included 15 studies (6109 participants); four (3070 participants) with newly-diagnosed, advanced EOC and 11 (3039 participants) with recurrent EOC. The studies varied in types of comparisons and evaluated PARPi. Eight studies were judged as at low risk of bias in most of the domains. Quality of life data were generally poorly reported. Below we present six key comparisons. The majority of participants had BRCA mutations, either in their tumour (sBRCAmut) and/or germline (gBRCAmut), or homologous recombination deficiencies (HRD) in their tumours.
Newly diagnosed EOC
Overall, four studies evaluated the effect of PARPi in newly-diagnosed, advanced EOC. Two compared PARPi with chemotherapy and chemotherapy alone. OS data were not reported. The combination of PARPi with chemotherapy may have little to no difference in progression-free survival (PFS) (two studies, 1564 participants; hazard ratio (HR) 0.82, 95% confidence interval (CI 0).49 to 1.38; very low-certainty evidence)(no evidence of disease progression at 12 months' 63% with PARPi versus 69% for placebo).
PARPi with chemotherapy likely increases any severe adverse event (SevAE) (grade 3 or higher) slightly (45%) compared with chemotherapy alone (51%) (two studies, 1549 participants, risk ratio (RR) 1.13, 95% CI 1.07 to 1.20; high-certainty evidence). PARPi combined with chemotherapy compared with chemotherapy alone likely results in little to no difference in the QoL (one study; 744 participants, MD 1.56 95% CI -0.42 to 3.54; moderate-certainty evidence).
Two studies compared PARPi monotherapy with placebo as maintenance after first-line chemotherapy in newly diagnosed EOC. PARPi probably results in little to no difference in OS (two studies, 1124 participants; HR 0.81, 95%CI 0.59 to 1.13; moderate-certainty evidence) (alive at 12 months 68% with PARPi versus 62% for placebo). However, PARPi may increase PFS (two studies, 1124 participants; HR 0.42, 95% CI 0.19 to 0.92; low-certainty evidence) (no evidence of disease progression at 12 months' 55% with PARPi versus 24% for placebo). There may be an increase in the risk of experiencing any SevAE (grade 3 or higher) with PARPi (54%) compared with placebo (19%)(two studies, 1118 participants, RR 2.87, 95% CI 1.65 to 4.99; very low-certainty evidence), but the evidence is very uncertain. There is probably a slight reduction in QoL with PARPi, although this may not be clinically significant (one study, 362 participants; MD -3.00, 95%CI -4.48 to -1.52; moderate-certainty evidence).
Recurrent, platinum-sensitive EOC
Overall, 10 studies evaluated the effect of PARPi in recurrent platinum-sensitive EOC. Three studies compared PARPi monotherapy with chemotherapy alone. PARPi may result in little to no difference in OS (two studies, 331 participants; HR 0.95, 95%CI 0.62 to 1.47; low-certainty evidence) (percentage alive at 36 months 18% with PARPi versus 17% for placebo). Evidence is very uncertain about the effect of PARPi on PFS (three studies, 739 participants; HR 0.88, 95%CI 0.56 to 1.38; very low-certainty evidence)(no evidence of disease progression at 12 months 26% with PARPi versus 22% for placebo). There may be little to no difference in rates of any SevAE (grade 3 or higher) with PARPi (50%) than chemotherapy alone (47%) (one study, 254 participants; RR 1.06, 95%CI 0.80 to 1.39; low-certainty evidence).
Four studies compared PARPi monotherapy as maintenance with placebo. PARPi may result in little to no difference in OS (two studies, 560 participants; HR 0.88, 95%CI 0.65 to 1.20; moderate-certainty evidence)(percentage alive at 36 months 21% with PARPi versus 17% for placebo). However, evidence suggests that PARPi as maintenance therapy results in a large PFS (four studies, 1677 participants; HR 0.34, 95% CI 0.28 to 0.42; high-certainty evidence)(no evidence of disease progression at 12 months 37% with PARPi versus 5.5% for placebo). PARPi maintenance therapy may result in a large increase in any SevAE (51%) (grade 3 or higher) than placebo (19%)(four studies, 1665 participants, RR 2.62, 95%CI 1.85 to 3.72; low-certainty evidence). PARPi compared with chemotherapy may result in little or no change in QoL (one study, 229 participants, MD 1.20, 95%CI -1.75 to 4.16; low-certainty evidence).
Recurrent, platinum-resistant EOC
Two studies compared PARPi with chemotherapy. The certainty of evidence in both studies was graded as very low. Overall, there was minimal information on the QoL and adverse events.
Authors' conclusions
PARPi maintenance treatment in women with first-line and platinum-sensitive recurrent disease improves progression-free survival (PFS) considerably, although it has less effect on overall survival (OS) and the OS results are less certain. PARPi maintenance increases severe adverse events, at times when women would otherwise not be on treatment, although quality of life may not be greatly impacted. The use of PARPi in other contexts did not lead to improved outcomes, especially in platinum-resistant recurrent disease. Adverse events and patient-reported outcomes were often poorly reported, which is a concern as this information is crucial for patient decision-making.
Funding
No dedicated funding
Registration
Protocol (2009) DOI: 10.1002/14651858.CD007929
Review (2010) DOI:10.1002/14651858.CD007929.pub2
Update (2015) DOI: 10.1002/14651858.CD007929.pub3
Update (2022) DOI: 10.1002/14651858.CD007929.pub4
