Introduction PRIMA trial results demonstrated efficacy and safety of niraparib first-line maintenance (1LM) in patients with epithelial ovarian cancer (EOC) who had a complete or partial response to first-line (1L) platinum-based chemotherapy. The ACTIV1ZE study used real-world laboratory data to describe platelet count testing frequency and time to decreased platelet count (DPC) among patients with EOC after 1LM niraparib initiation.

Methods This retrospective study used the nationwide Flatiron Health electronic health record-derived deidentified database. Adults with EOC diagnosed on/after 01Jan2015, who initiated 1LM niraparib monotherapy (01Apr2020­–03Jun2023) were included. Incidence of any-grade (<100,000/mcL) and grade ≥3 (<50,000/mcL) DPC were described during the index period (index date [1LM niraparib initiation] through the earliest of 30 days post-1LM niraparib completion or 2L treatment start).

Results Among 543 patients (median age, 67 years; 83.6% with advanced EOC at initial diagnosis), 24.9% had a DPC between 1L chemotherapy initiation and the index date. During the index period, 88.2% of patients had ≥1 platelet count test result; 36.8% and 21.7% of patients had any-grade or grade ≥3 DPC, respectively (table 1). Among patients who experienced a DPC, most (60.0%) any-grade DPCs initially occurred within 30 days of niraparib initiation. Median (IQR) time-to-any-grade DPC was 28 (22-44) days. Any-grade DPCs resolved in 98.0% of patients (median [IQR] time-to-resolution, 15 [12-22] days).

Conclusion/Implications DPC was likely to occur in patients with EOC within 30 days of initiation of 1LM niraparib monotherapy and resolved quickly. Results from this real-world study are consistent with findings from the PRIMA trial.