Trastuzumab, a monoclonal antibody, has been shown to improve the survival rates of patients diagnosed with HER2-positive breast cancer (HER2 + BC).

However, due to the high costs associated with biologic therapies such as trastuzumab, the development of biosimilars following patent expiration offers more affordable alternatives.

In this prospective, observational study, we assessed the effectiveness and safety of the biosimilar trastuzumab-dkst as adjuvant therapy for the first 59 Brazilian patients, out of a total of 176 enrolled. These patients represent an ethnically diverse population diagnosed with early-stage HER2 + BC.

At a follow-up of 31.7 months, the invasive disease-free survival rate was 94.5%, and the overall survival rate was 100% until the latest assessment, with no new safety concerns identified.

The introduction of trastuzumab-dkst as adjuvant therapy for HER2 + BC offers an opportunity to expand access to effective treatment.