A new report shows a longer time to first subsequent therapy (TFST) and improved second progression-free survival (PFS) among patients with newly diagnosed advanced ovarian cancer who received niraparib (Zejula) compared with placebo and who had previously responded to first-line chemotherapy.
These were key secondary end point findings from the phase 3 PRIMA clinical trial, presented by Sileny N. Han, MD, PhD, Department of Obstetrics and Gynecology, University Hospitals Leuven, Belgium, and colleagues at the 2020 Society of Gynecologic Oncology Annual Meeting on Women’s Cancer. Second PFS is defined as the time from initial study randomization to second disease progression or death from any cause.
Niraparib use previously demonstrated improved PFS, the primary end point of PRIMA, in patients after first-line platinum-based chemotherapy.
The US Food and Drug Administration has recently approved an additional indication for niraparib—for the maintenance treatment of adult patients with advanced epithelial ovarian, fallopian tube, or primary peritoneal cancer who have a complete response (CR) or partial response (PR) to first-line platinum-based chemotherapy.
The double-blind, placebo-controlled PRIMA clinical trial included 733 patients with newly diagnosed advanced ovarian, primary peritoneal, or fallopian tube cancer at highest risk for recurrence after demonstrating a CR or PR to first-line platinum-based chemotherapy. Patients were randomized 2:1 to receive niraparib or placebo once daily for 36 months or until disease progression. An interim analysis of the key secondary end points was based on the initial data cutoff of May 17, 2019.
In the overall population, patients randomized to niraparib had a median TFST that was 6.6 months longer than patients assigned to placebo (18.6 months vs 12.0 months; hazard ratio [HR], 0.65; P = .0001), reported Dr Han.
The improvement in median TFST in niraparib-treated patients was apparent regardless of biomarker status.
In patients with homologous recombination–deficient ovarian tumors, median TFST had not yet been reached for patients assigned to niraparib compared with 13.7 months in patients assigned to placebo (HR, 0.46; P <.0001).
In patients with homologous recombination–proficient tumors, the median TFST was 3.7 months longer in the niraparib arm compared with the placebo arm (11.6 months vs 7.9 months; HR, 0.64; P <.0105).
With data maturity in the overall population at 20%, the risk for second disease progression or death was approximately 20% lower in the niraparib arm versus the placebo arm, but the number of events was too low at the time to draw a definitive conclusion.
“These data are still immature, but the trends numerically favor niraparib treatment, especially in patients with HR-proficient tumors,” Dr Han noted. “Also, these data did not show any negative effect of niraparib treatment on subsequent therapy.”
In the overall PRIMA population, 37% of patients were still receiving niraparib compared with 28% in the placebo group at the time of primary analysis. Among the patients who had progressed, a higher proportion in the placebo group had received subsequent treatments compared with the niraparib group (51% vs 41%).
Interim analysis of overall survival favors niraparib, with 2-year overall survival at 84% in the niraparib arm versus 77% in the placebo arm, with the caveat that survival data are not mature, said Dr Han.