Real World Study of Biosimilar Trastuzumab in Her2 Positive Breast Cancer

Inclusion Criteria: * female patients aged 18 years and over * diagnosis of early stage I to III breast cancer confirmed by histopathology test according to local guidelines. * human epidermal growth factor receptor 2 (HER2)-positive tumor by immunohistochemistry or FISH (Fluorescence In Situ Hybridization), as per the 2018 ASCO assessment guideline \[J Clin Oncol 36:2105, 2018\]. * use of at least one dose of biosimilar trastuzumab (Zedora) as adjuvant therapy, regardless of previous neoadjuvant trastuzumab or Zedora use or the type of chemotherapy combined with the antibody. * Signing of the informed consent form (ICF). Exclusion Criteria: * use of biosimilar trastuzumab (Zedora) differently from the provisions in the label. * patients enrolled in and followed up by Programa Vida Plena \[Full Life Program\].