Estrogen Receptors and HER2 Levels' Expression in Luminal Metastatic Breast Cancer

Estrogen Receptors and HER2 Levels' Expression in Luminal Metastatic Breast Cancer: Correlation to Therapeutic Efficacy of Cycline-Dependent Kinase Inhibitors(CDK4/6) as First Line Treatment. CYCLHER Study

CYCLHER is a retrospective observational multicentric italian study aimed to evaluate the correlation between hormone receptors (HR) and HER2 immunohistochemistry (IHC) levels and treatment'response in patients affected by advanced breast cancer treated with first line CDK4/6 inhibitor plus endocrine therapy.

Inclusion Criteria:

• Age ≥ 18 yo
• Histological diagnosis of HR+/HER2- advanced breast cancer
• Immunohistochemical HER2 negative evaluation (0, 1+ or 2+ FISH-)
• Immunohistochemical expression levels of estrogen and progesterone receptors
• First line CDK4/6 inhibitor plus endocrine therapy stared up to 12/31/2020
• Signing of informed consent approved by local Ethic Committee

Exclusion Criteria:

• Absence of clinical and pathological data that would compromise the definition of the study endpoints
• HER2 positive (ICH 2+ and FISH positive or HER2 3 +) or triple negative disease
• Previous chemotherapy for treatment of metastatic disease