OBJECTIVES: This study evaluates the cost-effectiveness of combining Niraparib, a poly (ADP-ribose) polymerase (PARP) inhibitor, with abiraterone acetate and prednisone (AAP), versus AAP alone, in treating metastatic castration-resistant prostate cancer (mCRPC) in patients with homologous recombination repair (HRR) defects, especially those with BRCA 1/2 mutations.

METHODS: A partitioned survival model was utilized to analyze the treatment strategies over a 5-year horizon from a US payer perspective. Using TreeAge Healthcare Pro-2021, the model simulated patients transitioning through states of progression-free, disease progression, or death. Transition probabilities were extracted from the Magnitude III trial's Kaplan-Meier curves using a web plot digitizer and analyzed with the flexsurv package in R. Drug acquisition costs were sourced from the Department of Veterans Affairs' Federal Supply Schedule. Treatment costs, including outpatient administration, monitoring, follow-up, and management of adverse events, were sourced from published literature, and adjusted to 2023 US dollars using the US consumer price index. The effectiveness of interventions was measured in quality-adjusted life years (QALYs) using disease-specific health utility values from published literature. The incremental cost-effectiveness ratio (ICER) was calculated using a 3% discount rate and willingness to pay threshold (WTP) of $150,000. Deterministic and probabilistic sensitivity analyses were conducted to evaluate the robustness of the model.

RESULTS: The addition of niraparib to AAP yielded an increase of 0.23 QALYs at an additional cost of $70,193, resulting in an ICER of $306,890 per QALY in the BRCA 1/2 gene mutation subgroup. For the broader HRR+ cohort, the gain was 0.04 QALY, with an ICER of $1,906,857 per QALY. Sensitivity analyses identified the cost of niraparib and utility values of health states as the most influential parameters.

CONCLUSIONS: Niraparib combined with AAP is not cost-effective compared to AAP alone at the WTP threshold of $150,000 per QALY for mCRPC with gene mutation.