Treatment with niraparib improves progression-free survival (PFS) in patients with ovarian cancer regardless of their biomarker status.
In the treatment of patients with advanced ovarian cancer, niraparib monotherapy may represent a new opportunity after first-line platinum-based chemotherapy based on an updated analysis of the phase 3 PRIMA study. Trial data were presented at this year’s Society of Gynecologic Oncology Annual Meeting on Women’s Cancer.
Based on the exploratory analysis, treatment with niraparib improved PFS in patients regardless of their biomarker status. In the analysis, patients who received niraparib in all biomarker groups had a statistically significant and clinically meaningful PFS benefit; overall reduction in the risk of a progression event (hazard ratio [HR], 0.62; P <.0001) was 38%. As reported previously, in patients with homologous recombination deficiency, the risk of cancer recurrence or death was reduced by 57% in those who received niraparib compared with those who received placebo (P <.0001).
In patients with newly diagnosed advanced ovarian cancer after first-line platinum-based chemotherapy, including patients at the highest risk of relapse, niraparib previously showed an improvement in PFS. In the exploratory analysis of PRIMA presented, Bradley J. Monk, MD, FACOG, FACS, Gynecologic Oncologist, Arizona Oncology (US Oncology Network), Phoenix, and colleagues evaluated the efficacy of niraparib according to biomarker subgroups.
A total of 733 patients with newly diagnosed advanced ovarian, primary peritoneal, or fallopian tube cancer with a complete or partial response to first-line platinum-based chemotherapy were enrolled in the PRIMA clinical trial. Patients were randomized in a 2:1 ratio to niraparib or placebo once daily. Niraparib dosing was individualized for the remaining patients enrolled in the trial after nearly two-thirds of patients were enrolled.
Of the 733 patients randomized, 373 (51%) had homologous recombination deficiency and 249 (34%) had homologous recombination proficiency. In the subset of patients with BRCA mutations, niraparib reduced the risk of progression by 60% (HR, 0.40; P <.0001). In patients with BRCA wild-type mutation, the risk reduction was 50% (HR, 0.50; P = .0064).
The efficacy of niraparib for PFS was similar in patients with BRCA1 mutations (HR, 0.39; 95% confidence interval [CI], 0.23-0.66) and BRCA2 mutations (HR, 0.35; 95% CI, 0.15-0.84). The dose modification rate and the safety profile were similar to those of data reported in earlier trials of niraparib. No new safety signals were identified in the current trial as reported by researchers.
“I think all of us recognize that BRCA1 mutations are about twice as common as BRCA2. We realize that BRCA1 is more pathogenic, meaning the risk of breast and ovarian cancer is higher, and we also realize that BRCA1 patients are harder to treat with a PARP inhibitor,” said Dr Monk. “In this hypothesis-generating exploratory analysis, there was a consistent treatment effect in the BRCA1 and BRCA2 patients. This is an important new piece of information.”
Niraparib provided a significant benefit on PFS in patients in the homologous recombination–deficient subgroup. In addition, niraparib provided a 32% reduction in the risk of a PFS event (HR, 0.68; P = .0203) in patients in the homologous recombination–proficient subgroup.
The rate of grade ≥3 thrombocytopenia in the niraparib arm decreased from 36% to 15% after the niraparib dose was individualized, said Dr Monk. “So, there’s an opportunity here to individualize the dose based on weight and baseline platelet count. We have not shown the impact of outcomes for this, but stay tuned.”
Source: Monk BJ, et al. Gynecol Oncol. 2020;159(1_suppl). Abstract 31.