Biomarkers of response to neoadjuvant palbociclib plus anastrozole in endocrine-resistant estrogen receptor-positive/HER2-negative breast cancer: a phase 2 trial.

ABSTRACT: CDK4/6 inhibitors (CDK4/6i) improve outcomes for estrogen receptor (ER) positive/HER2-negative breast cancers (BCs), yet intrinsic and acquired resistance exist. Here, we evaluated anastrozole in combination with palbociclib (ANA/PAL) in the NeoPalAna Endocrine-Resistant cohort (NCT01723774). Thirty-four patients with clinical stage II/III ER + /HER2- BCs resistant to standard neoadjuvant endocrine therapy (on-treatment Ki67 > 10%) received neoadjuvant ANA/PAL, with serial biopsies analyzed. The primary endpoint, complete cell cycle arrest (CCCA; Ki67_C1D15 ≤ 2.7% at cycle 1, day 15), was achieved in 57.6% of patients (95%CI: 39.2-74.5%). Resistance to ANA/PAL (Ki67_C1D15 > 10%) was associated with higher pre-treatment tumor grade, Ki67, and specific PAM50 subtypes. Res

SUBMITTER: Kong T 

PROVIDER: S-EPMC12848104 | biostudies-literature | 2026 Jan

REPOSITORIES: biostudies-literature