Utidelone plus bevacizumab for the treatment of HER2-negative breast cancer brain metastases (U-BOMB): A multicenter, single-arm phase II study.

1081 Background: The primary treatment for brain metastases in patients with HER2-negative advanced breast cancer is predominantly local therapies like radiotherapy, owing to the limited efficacy of systemic therapies. Prior research has demonstrated utidelone's significant permeability across the blood-brain barrier and the preliminary effectiveness of bevacizumab for breast cancer brain metastases. Consequently, this study investigated the efficacy and safety of utidelone combined with bevacizumab in the treatment of advanced breast cancer brain metastases. Methods: This study was a single-arm, multi-center phase II clinical trial (NCT05357417). Eligible patients were aged 18 years or older with either radiotherapy-naive or progressive brain metastases post-radiotherapy, presented with asymptomatic or symptomatic brain metastases associated with HER2-negative breast cancer.Patients received intravenous bevacizumab (15 mg/kg on day 1 of each 3-week cycle) and utidelone (30 mg/m2 on days 1 to 5 of each cycle) until intolerance or disease progression. The primary endpoint was central nervous system objective response rate (CNS-ORR), as assessed according to the Response Evaluation Criteria In Solid Tumors version 1.1. Results: Between May 5, 2022, and October 25, 2023, a total of 46 patients were recruited, with a median age of 52.5 years (range, 33 to 69). Among them, 35 patients had untreated CNS lesions, while 11 had progressive brain metastases after local radiotherapy. The CNS-ORR was 43.5% (95% confidence interval [CI], 28.9%-58.9%). As of January 8, 2024, the median duration of follow-up was 14.6 months, and the median progression-free survival (PFS) was 7.7 months (95% CI: 5.5-10.8) as shown in Table. The 12-month overall survival (OS) rate reached 74.4% (95% CI: 60.0%-92.3%). The most common grade 1-2 adverse events (AEs) were peripheral neuropathy (87.5%), decreased neutrophil count (62.5%), anemia (47.5%), diarrhea (37.5%), and increased alanine aminotransferase (25%). No grade 3 or higher treatment-related AEs occurred. Conclusions: This study preliminarily shows promising efficacy and manageable safety of the combination of utidelone and bevacizumab in the treatment of HER2-negative metastatic breast cancer patients with brain metastases. Clinical trial information: NCT05357417 . [Table: see text]