Evaluation of the Safety and Efficacy of Trastuzumab Emtansine (T-DM1) Biosimilar in Human Epidermal Growth Factor Receptor 2 (HER2)-Positive Breast Cancer: Findings From a Single-Center Retrospective Analysis in India

Background Human epidermal growth factor receptor 2 (HER2)-positive breast cancer is a highly aggressive subtype characterized by a high recurrence rate. Trastuzumab emtansine (T-DM1), an antibody-drug conjugate targeting HER2, has shown improved outcomes; however, its effectiveness in cases with brain metastases remains unclear. The T-DM1 biosimilar has emerged as a cost-effective treatment option. Objectives The primary objective was to assess the efficacy of the T-DM1 biosimilar by evaluating progression-free survival (PFS) and overall survival (OS). The secondary objective focused on analyzing the safety profile, including the incidence and characteristics of adverse events (AEs) during T-DM1 treatment. Materials and methods In this retrospective, single-center study, 30 HER2-positive breast cancer patients were treated with T-DM1 at a dose of 3.6 mg/kg, administered intravenously every 21 days. The primary outcomes measured were PFS, OS, time to treatment failure (TTF), complete response (CR), and partial response (PR). The secondary endpoint was the documentation of AEs. Results All patients, with a median age of 57 years, received prior HER2-targeted therapy, and five (16.6%) patients had undergone brain radiotherapy. CR was achieved in 20 (66.6%) patients, while 10 (33.3%) patients attained PR. PFS, OS, and TTF were approximately 14, 24, and 13 months, respectively. Common adverse events included elevated transaminases, anemia, and thrombocytopenia, the majority of which were controllable and reversible. Conclusion This study provides important insights into the efficacy and safety of the T-DM1 biosimilar. The findings indicate that T-DM1 is effective in enhancing OS and managing advanced HER2-positive breast cancer, including selective patients with brain metastases. The results highlight the T-DM1 biosimilar as a cost-effective treatment option with an expected safety and tolerability profile.