Do women with ovarian cancer live longer if poly (ADP-ribose) polymerase inhibitors (PARPi) are used in their treatment, and do PARPi cause unwanted effects?
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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.
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.
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 treatmentPARPi 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.
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 EOCCompared 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.
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.