Real-world Bicohort Observational Study of a Pertuzumab Biosimilar in the Treatment of Breast Cancer: in the Neoadjuvant Setting and in First-line Metastatic Disease

Inclusion Criteria:

* Age ≥ 19 years at the time of inclusion;
* Histologically confirmed diagnosis of HER2-positive invasive breast cancer (IHC 3+ score or HER2 amplification by FISH/CISH/SISH);
* Decision to initiate treatment with a pertuzumab biosimilar in the neoadjuvant setting (neoadjuvant cohort) or as first-line therapy in the metastatic setting (metastatic cohort), in accordance with local indications;
* Treatment prescribed as part of routine clinical care (outside of a clinical trial);
* Patient informed and having provided written informed consent.

Exclusion Criteria:

* Treatment with pertuzumab in a therapeutic setting other than neoadjuvant or first-line metastatic (e.g., adjuvant, late recurrence beyond first-line, maintenance therapy alone, etc.);
* Treatment administered as part of an interventional clinical trial;
* History of severe allergy or known contraindication to pertuzumab;
* Medical records unavailable or inability to ensure at least 6 months of minimal follow-up.