ECLECTIC: EstroTEP and Circulating Biomarkers for ER-positive HER2-negative Metastatic Breast Cancer Patients

Consist in single agent endocrine therapy or in combination with targeted therapy, per guidelines and label. LH-RH agonist will be used in combination with endocrine therapy whenever appropriate and per label.

Consist in single agent endocrine therapy or in combination with targeted therapy, per guidelines and label. LH-RH agonist will be used in combination with endocrine therapy whenever appropriate and per label. Cases with only 1 or 2 FES-negative lesions that are accessible to local treatment will be reviewed by the Centralized Reading Committee (including a radiation oncologist) to confirm the feasibility of local treatment.

Consist in single agent chemotherapy, poly-chemotherapy, or antibody-drug conjugates, per guidelines and label. Patients who are eligible (per drug label) may receive PARP inhibitor if allocated to Arm B.