Preliminary data on time to first subsequent therapy (TFST) and second progression-free survival suggest a clinical benefit of niraparib therapy in a broad population of patients with ovarian cancer following response to first-line chemotherapy. Second progression-free survival is defined as the time from initial study randomization to second disease progression or death from any cause. These findings come from the phase 3 PRIMA study, presented by Sileny N. Han and colleagues at the Society of Gynecologic Oncology (SGO) Annual Meeting on Women’s Cancer.
“Niraparib provided a long-term benefit across a broad population of patients with ovarian cancer, and treatment benefit persisted beyond the first progression,” she reported.
Niraparib previously demonstrated improved progression-free survival in patients with newly diagnosed advanced ovarian cancer after first-line platinum-based chemotherapy in the PRIMA trial. This analysis explored key secondary end points; interim analysis of these end points was presented based on the initial data cutoff of May 17, 2019.
The double-blind, placebo-controlled trial included 733 patients with newly diagnosed advanced ovarian, primary peritoneal, or fallopian tube cancer at highest risk of recurrence after demonstrating a complete response (CR) or partial response (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. Stratification factors were best response to first-line chemotherapy (CR/PR), receipt of neoadjuvant chemotherapy (yes/no), and homologous recombination status (deficient [HRd] or proficient [HRp]). The study’s primary end point was progression-free survival, assessed by blinded independent central review, with key secondary end points of TFST and second progression-free survival.
In the overall population, patients receiving niraparib had a median TFST that was 6.6 months longer than patients given placebo (18.6 months vs 12.0 months; hazard ratio, 0.65; P = .0001). This benefit was seen regardless of biomarker status, reported Dr Han, from the Department of Obstetrics and Gynecology at University Hospitals Leuven, Belgium.
In HRd patients, median TFST had not yet been reached for patients receiving niraparib compared with 13.7 months in patients receiving placebo (hazard ratio, 0.46; P <.0001).
In HRp patients, the median TFST was 3.7 months longer in patients receiving niraparib than those given placebo (11.6 months vs 7.9 months; hazard ratio, 0.64; P <.0105).
With 20% data maturity in the overall population, second progression-free survival data show an almost 20% reduction in the risk of second disease progression or death with niraparib therapy, regardless of biomarker status. However, second progression-free survival event rates are low, so definitive conclusions cannot be drawn. According to Dr Han, updated data will be presented at a future meeting.
“These data are still immature, but the trends numerically favor niraparib treatment, especially in patients with HRp tumors,” she noted. “Also, these data did not show any negative effect of niraparib treatment on subsequent therapy.”
In the overall 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 (51%) had received subsequent treatments compared with the niraparib group (41%). After progression, the majority of patients received a platinum-based regimen.
Interim analysis of overall survival also numerically favors niraparib over placebo, the investigators reported. Overall survival at 2 years in the overall population was 84% versus 77% with niraparib and placebo, respectively. “However, we acknowledge again that the data are not mature, and these will be updated at a later time,” added Dr Han.
SGO 2020 Annual Meeting on Women’s Cancer. Abstract 32. Presented April 29, 2020.