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Niraparib showed antitumor activity in a small group of patients with localized HER2-negative breast cancer harboring a BRCA1/2 mutation who were enrolled in a single-arm pilot study. The study results were reported at the 17th St. Gallen International Breast Cancer Conference 2021.
The trial (ClinicalTrials.gov Identifier: NCT03329937) enrolled 21 treatment-naive patients with localized HER2-negative breast cancer harboring a BRCA1/2 mutation. All patients received niraparib, a poly (ADP-ribose) polymerase (PARP) inhibitor.
Most patients (71.4%) had triple-negative breast cancer, and the rest (28.6%) had hormone receptor-positive disease. Two-thirds of patients had a BRCA1 mutation, and 28.6% had a BRCA2 mutation. One patient had both a BRCA1 and a BRCA2 mutation.
The tumor response rate was 90.5%, which included 2 complete responses and 17 partial responses, as assessed by magnetic resonance imaging (MRI). Tumor response was also assessed by ultrasound, which yielded a 95.2% response rate that included 1 complete response and 19 partial responses.
A median reduction in tumor volume of 86.4% (range, 26-100) was seen on MRI, and ultrasound showed a similar median reduction of 87.2% (range, 23-100).
The most common treatment-related adverse events of any grade were nausea (66.7%), fatigue (47.6%), and anemia (23.8%). One-third of patients reported a grade 3 or worse treatment-related adverse event, the most common being anemia (14.3%), neutropenia (9.5%), and decrease in neutrophil count (9.5%).
Overall, 19% of patients required a reduction in niraparib dose. No treatment discontinuations due to a treatment-related adverse event were reported.
The study authors concluded that niraparib showed “promising” antitumor activity in the neoadjuvant treatment of patients with localized HER2-negative, BRCA-mutated breast cancer.
Disclosure: Study authors declared affiliations with and receipt of funding from the pharmaceutical industry, and this study was funded by GlaxoSmithKline. Please refer to the original article for a full list of disclosures.
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Spring LM, Han H, Hamilton E, et al. Neoadjuvant niraparib in patients with HER2-negative, BRCA-mutated resectable breast cancer. Poster presentation at: 17th St. Gallen International Breast Cancer Conference 2021; March 17-21, 2021. Abstract P095.