A Study for CTC Expression and cfDNA/RNA Assessment in Metastatic Breast Cancer Patients

A prospective, multicenter, observational study of CellSearch CTC enumeration, CTC HER2, ER, and PD-L1 expression, and MSearch cfDNA/RNA results in subjects with histologically proven MBC. Treatment for MBC will be chosen and performed by treating physicians/providers. Eligible subjects will be enrolled after signing the ICF. Subjects will receive CTC enumeration, CTC HER2, ER, PD-L1 expression and, and MSearch cfDNA/RNA assessments at baseline and first restaging as part of Standard of Care (SoC). Subjects will receive any additional cfDNA/RNA assessments as part of research collection. For all subjects 4 to 6 tubes will be collected at baseline and minimally before the first restaging visit. For any subsequent restaging visits a total of 3 to 4 tubes will be collected.

Inclusion criteria

• 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.

OR HER2+ subjects prior to starting second 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.

Exclusion criteria

• Participant is pregnant.
• Inability to provide blood samples based on the judgment of the treating physician.