Endocrine therapy in early-stage estrogen Receptor-Low breast cancer: a systematic review and Meta-Analysis.
BACKGROUND Tumors with ≥1% estrogen receptor (ER) expression by immunohistochemistry (IHC) are classified as hormone receptor-positive. While this definition includes ER-low tumors (ER 1-9%), the clinical benefit of endocrine therapy (ET) in ER-low early-stage breast cancer (BC) remains uncertain. METHODS This is a s...