When should poly (ADP‑ribose) polymerase (PARP) inhibitors be used in ovarian cancer?

PARP Inhibitor Use in Ovarian Cancer

PARP inhibitors should be used as maintenance therapy in newly diagnosed stage III-IV high-grade serous or endometrioid ovarian cancer after achieving complete or partial response to first-line platinum-based chemotherapy, with specific agent selection based on BRCA mutation status, HRD status, and bevacizumab use. 1

First-Line Maintenance Therapy (Newly Diagnosed Stage III-IV Disease)

For Patients WITHOUT Prior Bevacizumab

If BRCA1/2 mutation present (germline or somatic):

• Olaparib 300 mg orally every 12 hours for 2 years (Category 1 recommendation) 1
• Niraparib 200-300 mg orally daily for 3 years (Category 1 recommendation) 1
• Both options have high-quality evidence demonstrating substantial PFS benefits 1

If BRCA wild-type:

• Niraparib 200-300 mg orally daily is the preferred option for all-comers regardless of biomarker status 1
• The PRIMA trial demonstrated significant PFS improvement in the overall population, with even greater benefit in HRD-positive subgroups 1
• Rucaparib monotherapy is also an option based on panel consensus, though not FDA-approved for this indication 1

For Patients WITH Prior Bevacizumab

If BRCA1/2 mutation OR HRD-positive (by Myriad myChoice CDx):

• Olaparib 300 mg every 12 hours PLUS bevacizumab continuation (Category 1 recommendation) 1
• The PAOLA-1 trial demonstrated significant PFS benefit in BRCA-mutated and HRD-positive subgroups 1
• Critical caveat: No statistically significant benefit was seen in HRD-negative tumors (HR 1.00) 1

If BRCA wild-type without confirmed HRD:

• Olaparib or niraparib monotherapy are Category 2A options 1
• Niraparib plus bevacizumab may be considered for patients unable to tolerate olaparib 1

Important Considerations for First-Line Maintenance

HRD testing is strongly recommended for patients without germline BRCA1/2 mutations, as it provides information on magnitude of benefit 1. The median survival benefit in HRD-negative (homologous recombination proficient) patients is approximately 3 months, which the NCCN panel considers minimal benefit 1.

Stage II disease: The same maintenance recommendations apply to stage II high-grade serous or endometrioid ovarian cancer, though data is limited 1.

Early-stage disease (Stage I-II): PARP inhibitors are NOT recommended due to insufficient evidence 1

Recurrent/Platinum-Sensitive Disease (Second-Line or Later Maintenance)

Current FDA-Approved Indications (Post-2023 Restrictions)

PARP inhibitors as second-line maintenance therapy are now restricted to patients with germline or somatic BRCA mutations only 1. The FDA requested voluntary withdrawal of broader indications due to concerns about possible OS reductions in BRCA wild-type patients in retrospective analyses 1.

Approved options for BRCA-mutated recurrent disease:

• Olaparib 300 mg every 12 hours 1
• Niraparib 200-300 mg once daily 1
• Rucaparib 600 mg every 12 hours 1

All three agents demonstrated significant PFS benefits in platinum-sensitive recurrent disease after CR/PR to platinum-based therapy 1. The SOLO2 trial showed olaparib extended OS by approximately 13 months in BRCA-mutated recurrent disease (51.7 vs 38.8 months; HR 0.74) 1.

Treatment Setting (Third-Line or Beyond)

PARP inhibitor monotherapy may be offered to patients with recurrent EOC who have germline or somatic BRCA1/2 mutations and have not previously received a PARP inhibitor 1. Options include the same three agents at standard dosing 1.

Critical Contraindications and Caveats

Repeating PARP inhibitor therapy is NOT recommended at this time due to insufficient evidence 1. Clinicians should carefully consider the optimal timing in a patient's disease course to use PARP inhibitors, as re-exposure data is lacking 1.

Veliparib cannot be recommended despite VELIA trial data, as it remains commercially unavailable and the study design lacked a chemotherapy-plus-placebo comparator arm 1

Histologic restrictions: Recommendations specifically apply to high-grade serous or grade 2/3 endometrioid cancer types 1. Evidence for other histologies (clear cell, mucinous, low-grade serous, carcinosarcoma) is lacking 1.

Common pitfall: Do not substitute PARP inhibitors interchangeably in combination regimens, as safety, dosing, and duration have not been established for off-label combinations 1. Olaparib with carboplatin requires dose modifications 1.

Biomarker Testing Algorithm

1. Test all patients for germline BRCA1/2 mutations at diagnosis 1
2. If germline testing negative, perform somatic tumor testing for BRCA1/2 mutations 1
3. If BRCA wild-type, perform HRD testing (e.g., Myriad myChoice CDx) to guide treatment decisions, particularly if bevacizumab combination is being considered 1

The panel acknowledges current HRD tests are imperfect proxy measures lacking full accuracy in predicting functional HRD, but they provide valuable prognostic information 1.