The purpose of this research is to learn if the CellSearch Circulating Tumor Cells (CTC) test can help doctors in making decisions about treatment and monitoring of breast cancer. The test consists of diagnostic CTC counts (enumeration) and expression of biomarkers Human Epidermal growth factor Receptor 2 (HER2), Estrogen Receptor (ER), and programmed death-ligand 1 (PD-L1) and cell free DNA/RNA (cfDNA/RNA) analysis.
Invasive breast cancer with radiographic and/or clinical evidence of advanced metastatic or unresectable disease.
HR+/HER2 negative or triple negative (TN) subjects prior to starting first line therapy or beyond in the metastatic setting.
Subject must have the CTC HER2, ER, PD-L1, and cfDNA/RNA tests ordered during routine patient care.
Age > 18 years.
Participant is pregnant.
Inability to provide blood samples based on the judgment of the treating physician.