Prognostic value of hormone receptor expression in patients with HR+/HER2− advanced BC treated with first-line ET+CDK4/6i: results from the multicentre observational, real-world PALMARES-2 study

Summary: Background: Endocrine therapy (ET) plus Cyclin Dependent Kinase 4/6 inhibitors (CDK4/6i) is the recommended first-line treatment for patients with Hormone Receptor-positive, Human Epidermal growth factor Receptor 2-negative advanced Breast Cancer (HR+/HER2− aBC). The prognostic value of the spectrum of Oestrogen Receptor (ERα) and Progesterone receptor (PgR) expression remains poorly investigated in this setting.