HER2-low Unresectable and/or Metastatic Breast Cancer in Russia

Inclusion Criteria:

• Patients with confirmed diagnosis of unresectable and/or metastatic BC establishedbetween the 1st July 2021 and the 1st July 2022.

• Patients have HER2-negative status (IHC0, IHC1+, IHC2+/ISH-) obtained in the locallaboratory.

-. Patients have an adequate archival tumor sample and slides suitable forreassessment HER2 status* by the reference laboratory.

• Patients have documented hormonal status (ER, PR) IHC score.

• Age ≥ 18 years at the time of inclusion.

• Patients provided written consent allowing for data and samples to be used in thefuture and this study would be covered by the consent for future use in accordancewith ICH GCP, GPP (Good Pharmacoepidemiology Practices) and local law prior toinclusion in the study. If the patient is deceased, a waiver may be accepted

Exclusion Criteria:

• Patients with previous HER2 positive status in the anamnesis at the diagnosis orafter the diagnosis of breast cancer.

• Presence of other malignancies within period since diagnosis until the timepoint ofdata collection.

• Patients receiving trastuzumab deruxtecan currently or received in anamnesis.

• The participation in any randomised controlled trial within period since diagnosisuntil end of study.