This multi-center observational retrospective study will collect real-world clinical data from eligible patients with unresectable or metastatic HER2+ breast cancer who have received one or more cycles Trastuzumab Deruxtecan in Russian Federation

This multi-center observational retrospective study will collect real-world clinical data from eligible patients with unresectable or metastatic HER2+ breast cancer who have received one or more cycles Trastuzumab Deruxtecan in Russian Federation

The aim of this trial is to explore the real-world effectiveness T-Dxd and potential predictors in Russian metastatic breast cancer patients

Inclusion Criteria:

1. Patients aged over 18 years old.
2. Metastatic breast cancer included unresectable locally advanced breast cancer, de novo stage IV breast cancer, and recurrent metastatic breast cancer.
3. Patients has received Trastuzumab Deruxtecan
4. Available medical history.

Exclusion Criteria:

1. Incomplete medical history.
2. Pregnancy or breast-breeding