Starting dose of niraparib as first-line maintenance among patients with newly diagnosed advanced ovarian cancer in a real- world database (352)

Abstract

<b>Objectives:</b> Niraparib is the only poly (adenosine diphosphate [ADP]- ribose) polymerase inhibitor that is FDA-approved as monotherapy in first-line (1L) ovarian cancer (OC) maintenance regardless of biomarker status with an individualized starting dose (ISD). For patients weighing <77 kg (<170 lb) or with a platelet count <150,000/μL, the recommended starting dose is 200 mg taken orally once daily rather than the standard 300 mg dose. This study evaluated the uptake of the new ISD of niraparib using the Flatiron Health database in 1L OC maintenance. <b>Methods:</b> This retrospective cohort study included patients with newly diagnosed stage III/IV epithelial OC whose last 1L platinum-based chemotherapy (PBC) dose was between January 1, 2017, and February 28, 2021, from the nationwide Flatiron Health electronic health record- derived database. The de-identified data originated from approximately 280 US cancer clinics during the study period. Patients who started a second-line chemotherapy treatment within two months of the last 1L PBC dose were excluded. Starting doses of niraparib, according to weight and platelet count, were assessed among patients receiving niraparib monotherapy as 1L maintenance therapy. <b>Results:</b> Among patients with newly diagnosed advanced OC, 64 patients (median age: 66 years [Q1:60; Q3:74]) received niraparib monotherapy for 1L maintenance. The median time between initiation of maintenance therapy and the last 1L PBC dose was 49 days (Q1:38; Q3:77). The mean weight of patients receiving niraparib monotherapy was 70.2 kg (standard deviation [SD]: 15.3). In total, 40 patients (62.5%) had platelet counts ≥150,000/μL and 20 patients (31.3%) had platelet counts <150,000/μL. Median and mean platelet counts were 178,500/μL (Q1:127,500; Q3:252,000) and 209,296/μL (SD: 120,096), respectively. Platelet counts were missing for four patients. Among 45 patients who met the criteria for the lower dose, 25 (55.6%) initiated niraparib at the correct dose of 200 mg, and 16 (35.6%) initiated niraparib at 300 mg (Table 1). Dosing information was missing for four patients. Among 15 patients who weighed >77 kg and had a platelet count ≥150,000/μL, 12 (80.0%) initiated at the correct dose of 300 mg and two (13.3%) initiated at 200 mg. Dosing information was missing for one patient. After the ISD recommendation (April 29, 2021), the use of the 200 mg dose increased from 22.7% to 57.9% in the overall group. However, in those who met the weight and platelet criteria, it increased from 35.7% to 64.5%. Table 1 <b>Conclusions:</b> Despite the benefits of the individualized starting dose, over 25% of OC patients who were eligible were not receiving the lower dose. Further studies are needed to better understand and educate oncologists on the option of personalized dosing of PARP inhibitors.