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    Palbociclib Regimen in HR+/HER2+ Breast Cancer With Brain Metastases: Phase 2 Trial Results

    Chen et alClinical cancer research : an official journal of the American Association for Cancer Research

    Palbociclib Regimen in HR+/HER2+ Breast Cancer With Brain Metastases: Phase 2 Trial Results
    Patients with hormone receptor-positive (HR+) and human epidermal growth factor receptor 2-positive (HER2+) advanced breast cancer face an elevated risk of brain metastases, with limited prospective evidence guiding systemic therapy. Eligible participants had HR+/HER2+ advanced breast cancer with measurable brain metastases and no prior local treatment to target lesions. Treatment continued until disease progression, unacceptable toxicity, or death.
    Between December 2020 and February 2026, 32 patients were enrolled, with final results reported for this cohort. Among the 29 response-evaluable patients, the primary endpoint of confirmed central nervous system objective response rate (CNS-ORR) was 58.6% (95% CI: 40.7–74.5), and the overall ORR was 62.1% (95% CI: 44.0–77.3). With a median follow-up duration of 32.5 months, median CNS progression-free survival (CNS-PFS) was 9.6 months (95% CI: 5.3–13.9), and median overall PFS was 12.3 months (95% CI: 6.8–17.7). Overall survival data remained immature with 5 deaths recorded, corresponding to a 24-month OS rate of 80.7%.
    Post-hoc analyses suggested numerically better PFS and CNS-PFS in chemotherapy-naïve patients, whereas prior trastuzumab exposure did not impair efficacy. The safety profile revealed that the most frequent grade ≥3 adverse events were diarrhea (37.5%), neutropenia (28.1%), and leukopenia (15.6%). There were no treatment-related deaths. The authors concluded that this quadruple systemic regimen showed promising intracranial activity, systemic disease control, and manageable toxicity in this patient population.

    Key Takeaways

    • In response-evaluable patients with HR+/HER2+ advanced breast cancer and brain metastases, the chemotherapy-sparing quadruple regimen yielded a confirmed central nervous system objective response rate of 58.6% (95% CI: 40.7–74.5) and an overall objective response rate of 62.1% (95% CI: 44.0–77.3).
    • At a median follow-up of 32.5 months, the median CNS progression-free survival was 9.6 months (95% CI: 5.3–13.9), median overall progression-free survival was 12.3 months (95% CI: 6.8–17.7), and the 24-month overall survival rate was 80.7%.
    • Grade 3 or higher adverse events included diarrhea in 37.5%, neutropenia in 28.1%, and leukopenia in 15.6% of patients, with no treatment-related deaths reported.
    Read the original sourceClinical cancer research : an official journal of the American Association for Cancer Research