There is a lack of data on clinical and patient factors that are associated with poor survival in patients with HR+ and HER2-low/negative breast cancer treated with neoadjuvant chemotherapy or endocrine therapy. This retrospective, non-interventional study is designed to assess the predictors of clinical outcomes in this patient population. No study drug will be provided as part of this study protocol.

This retrospective, non-interventional study is designed to assess the following primary objectives:

1. To identify predictors of event-free survival (EFS) in patients with HR+ and HER2-low/negative breast cancer treated with neoadjuvant chemotherapy or endocrine therapy, and
2. To stratify patients according to event-free survival using different combinations of significant predictors and evaluate the patient characteristics and clinical outcomes such as EFS, overall survival and pathological complete response across patient groups of different risk level.

Inclusion Criteria:

• Newly diagnosed HR+ and HER2-low/negative breast cancer diagnosed between January 1, 2010 and December 31, 2022 (Aged ≥18 years at the time of diagnosis)
• Stage I-IIIB at the time of diagnosis
• Received neoadjuvant chemotherapy and/or endocrine therapy and/or IO therapy
• Received curative intent surgery (mastectomy after neoadjuvant chemotherapy, endocrine, or IO therapy)

Exclusion Criteria:

• Patients who received HER2-targeted therapies including

  • Trastuzumab
  • Pertuzumab
  • Ado-trastuzumab emtansine
  • Neratinib
  • Tucatinib
  • Lapatinib
  • Fam-trastuzumab deruxtecan-nxki
  • Margetuximab

Patients with HR+ and HER2-low/negative breast cancer diagnosed between January 1, 2010 and December 31, 2022 and treated with neoadjuvant chemotherapy or endocrine therapy will be identified from the ConcertAI database based on the inclusion and exclusion criteria.