ER-positive breast cancer

ER-positive breast cancer: Tumor cells express estrogen receptors and rely on estrogen for growth. Generally has better prognosis and responds well to endocrine therapy (e.g., tamoxifen, aromatase inhibitors, fulvestrant).

Key for pharmacists: ER+ status guides use of hormonal therapy ± targeted therapy, often less chemo-intensive unless high-risk (e.g., high Ki-67, high grade).