Observational Study on the Treatment of Patients With Metastatic Breast Cancer

This is a descriptive, retrospective, observational study to generate Real-World Evidence (RWE). This study will evaluate the treatment patterns and outcomes with metastatic or unresectable hormone receptor-positive breast cancer in Brazil. No hypotheses will be tested.

This project aims to understand treatment patterns and outcomes in individuals with hormone receptor-positive \[HR-positive will be defined as Estrogen Receptor (ER) ≥ 1%\] and HER2-negative (HER2-Negative will be defined as IHC 0, 1+ and 2+/ISH-) unresectable or metastatic breast cancer (mBC) in Brazil.

Ten Brazilian centers will participate. This study will consist of a convenience cohort; will be included 200 patients. Adult patients who had received treatment in the participant Brazilian centers, with mBC ER-positive (i.e. ER ≥ 1%) and HER2-negative (i.e. HER2 IHC 0, 1 or 2+ with negative ISH), and who had received any CDK4/6i as first-line treatment with any outcome (death, progressive disease, or drug interruption due to any cause) since January 2018 will be enrolled. Data will be extracted from digital charts of Brazilian participating institutions. Patients who were treated with a CDK4/6i since January 2018 will be enrolled.

Eligibility Criteria:
Inclusion Criteria:

* Patient or next of kin/legal representative willing and able to provide written informed consent according to the local regulations unless a waiver is granted by the local IRB/IEC/EC;

  * Adult female or male patients ≥18 years old;
  * Unresectable or metastatic breast cancer; Estrogen Receptor ≥ 1% at the moment first-line treatment was initiated, either in a biopsy immediately before starting treatment for metastatic disease or in the biopsy of initial breast cancer diagnosis if a new biopsy was not performed;
  * HER2-negative (IHC 0, 1+ or 2+/ISH negative) at the moment first-line treatment was initiated, either in a biopsy immediately before starting treatment for metastatic disease or in the biopsy of initial breast cancer diagnosis if a new biopsy was not performed;
  * Have received treatment with a CDK4/6i in the first-line treatment for unresectable or metastatic breast cancer;
  * Have discontinued permanently the treatment with CDK4/6 for any reason: progressed disease on first-line treatment, died during first-line treatment due to any cause, or interrupted treatment for any reason;
  * Patients with recurrent disease are not mandated to have a new biopsy at the time of recurrence

Exclusion Criteria:

- Patients with recurrent disease with a primary tumor showing a different pattern of receptors (i.e. initial BC other than ER ≥ 1% and HER2 negative (IHC 0, 1+ or 2+/ISH negative);

* Patients with a concomitant cancer at the time of the diagnosis of MBC HR-positive HER2-negative except for the non-metastatic non-melanoma skin cancers, or in situ or benign neoplasms; a cancer is considered concomitant if it occurs within 5 years of HR-positive HER2-negative BC diagnosis;
* Patients who at time of data collection for this study are participating or have participated in an interventional study that remains blinded.