Long-Term Outcomes and Durability of Exceptional Responses to PARP Inhibitors in Recurrent Platinum-Sensitive Ovarian Cancer

Highlight

This international cohort study investigates long-term outcomes in patients with platinum-sensitive recurrent ovarian cancer (PS-ROC) experiencing exceptional responses to poly(adenosine diphosphate-ribose) polymerase (PARP) inhibitors maintained over 5 years. Key findings include remarkably high progression-free survival (PFS) rates at 7.5 and 10 years, evidence supporting potential treatment discontinuation without disease progression, low incidence of late-onset myelodysplastic syndrome (MDS) or acute myeloid leukemia (AML), and genotype enrichment in the BRCA1 and BRCA2 functional domains among exceptional responders.

Study Background

Ovarian cancer remains a leading cause of gynecologic cancer mortality worldwide, especially due to frequent recurrences despite initial platinum-based chemotherapy. Maintenance therapy with PARP inhibitors has transformed treatment paradigms for patients with platinum-sensitive recurrent ovarian cancer, significantly prolonging progression-free intervals. However, there remains uncertainty surrounding the optimal duration of PARP inhibitor maintenance, particularly in patients who demonstrate exceptional response profiles with durable disease control. Additionally, concerns regarding cumulative toxicity, especially the risk of therapy-related hematologic malignancies such as MDS and AML, warrant careful long-term evaluation. Identifying genotype-phenotype correlations may further optimize personalized treatment strategies and inform clinical decision-making in this population.

Study Design

This retrospective, international, multicenter cohort study assembled 320 patients documented to have exceptional response to PARP inhibitors, defined as progression-free survival of at least 5 years after treatment initiation. Patients were recruited from 41 sites across 14 countries between January 2023 and November 2025. The cohort’s mean age was 56.4 years. Patient treatment details, including duration of PARP inhibitor exposure, reasons for discontinuation (if applicable), toxicities, and survival outcomes, were extracted and analyzed. The primary endpoint was progression-free survival, with secondary outcomes encompassing overall survival, adverse effects, dose modifications, and late-onset hematologic complications. Molecular profiling was performed to assess genetic variants, focusing on BRCA1 and BRCA2 domains.

Key Findings

The median duration of PARP inhibitor therapy was 75 months (IQR 64-91 months), reflecting prolonged maintenance of therapy in many patients. Among those classified as exceptional responders:

• 65.9% (211/320) maintained continuous PARP inhibitor therapy.
• 34.1% (109/320) discontinued treatment for various reasons, including physician recommendation (10.6%), toxicity (6.9%), patient preference (5.3%), disease progression beyond 5 years (7.5%), or other causes (3.8%).

Remarkable progression-free survival rates were observed, with 7.5-year PFS reaching 88.8% (95% CI, 84.5%-93.3%) and 10-year PFS at 78.7% (95% CI, 70.5%-87.9%). Notably, among patients who discontinued PARP inhibitors for reasons other than progression (26.6%), the 10-year PFS was slightly higher at 90.1% (95% CI, 80.6%-100%) compared to 72.5% (95% CI, 60.3%-87.2%) in those continuing therapy.

Overall survival data corroborated durable disease control in this exceptional responder cohort. Toxicity-driven dose reductions and discontinuations were relatively infrequent. Importantly, only five patients (1.6%) developed late-onset MDS or AML, demonstrating a low risk of these serious hematologic events in long-term PARP inhibitor recipients.

Molecular analyses revealed a significant enrichment of pathogenic variants located specifically in the BRCA1 RING domain and the BRCA2 DNA-binding domain among exceptional responders. This observation provides insight into genotype-phenotype correlations that may underpin uniquely favorable responses to PARP inhibition.

Expert Commentary

This study addresses an important clinical knowledge gap regarding the management of PS-ROC patients who achieve outstanding long-term control with PARP inhibitors. The large international sample size and extended follow-up strengthen the reliability of the findings. The data challenge the necessity of indefinite PARP inhibitor therapy, suggesting that certain patients may safely discontinue maintenance therapy without compromising long-term outcomes. This aligns with emerging concepts of “functional cure” in subsets of ovarian cancer patients, who sustain prolonged remission after finite therapy.

While the low incidence of secondary hematologic malignancies is reassuring, continued vigilance remains essential given the cumulative exposure. Notably, the identification of specific BRCA domain variants enriched in exceptional responders highlights the potential to refine patient selection and tailor treatment duration. Future prospective trials to investigate discontinuation strategies and biomarker-driven personalization are warranted.

Limitations intrinsic to retrospective design, potential selection bias, and lack of standardized discontinuation criteria should be acknowledged. Moreover, mechanistic understanding of how distinct BRCA domain mutations confer superior PARP inhibitor responsiveness requires further biological exploration.

Conclusion

The findings from this comprehensive multicenter study offer critical evidence informing the duration and safety of PARP inhibitor maintenance in patients with platinum-sensitive recurrent ovarian cancer demonstrating exceptional response. Continued therapy beyond 5 years may not be necessary for all, with some patients maintaining durable progression-free survival after treatment cessation. The incidence of serious hematologic adverse events remains low, supporting long-term tolerability. Molecular profiling focusing on BRCA1 and BRCA2 domains could optimize therapeutic decision-making. These insights equip oncologists with data to guide individualized patient counseling and foster a paradigm shift towards personalized maintenance strategies in ovarian cancer.

Funding and ClinicalTrials.gov

The original study involved multiple international centers and the Gynecologic Cancer InterGroup Collaboration Into Exceptional Responders to PARP Inhibitors (GCIG-CERP). Detailed funding disclosures were not provided. The study is registered under PMID 42348196. No ClinicalTrials.gov identifier was noted.

References

• 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 Oncol. 2026 Jun 25. PMID: 42348196.
• Kurzrock R, Stewart DJ. Poly (ADP-ribose) polymerase (PARP) inhibitors: a new cornerstone in ovarian cancer treatment. J Clin Oncol. 2022;40(16):1749–1757.
• Robson M, Im SA, Senkus E, et al. Olaparib for Metastatic Breast Cancer in Patients with a Germline BRCA Mutation. N Engl J Med. 2017;377(6):523-533.
• Moore K, Colombo N, Scambia G, et al. Maintenance Olaparib in Patients with Newly Diagnosed Advanced Ovarian Cancer. N Engl J Med. 2018;379(26):2495-2505.