Mark Verrill, MA, MB, BChir, FRCP from the Newcastle Upon Tyne Hospitals NHS Foundation Trust, Newcastle Upon Tyne, UK, discusses the use of trastuzumab and biosimilars in breast cancer treatment at the 2017 British Society for Hematology (BSH) Annual Scientific Meeting in Brighton, UK. Trastuzumab is a versatile drug, that can be used in many different ways. It is primarily used in the neoadjuvant therapy to shrink the tumour before surgery, however, it can be used in the post-operative adjuvant setting with either chemotherapy or endocrine therapy, and at all stages of metastatic disease. When registering a biosimilar, one indication is usually selected with which to compare it to the original, the most robust being the neoadjuvant setting. Once strong data has been found, it will likely be licensed across the board for all clinical indications. This video has been supported by Napp Pharmaceuticals Ltd through an unrestricted educational grant to Magdalen Medical Publishing.