Abstract
Globally, breast cancer is the most frequently diagnosed malignancy and the leading cause of oncological death in women. Metastatic disease at diagnosis (de novo stage IV breast cancer) will be identified in about 5% of patients. Treatment options vary based on several factors, namely whether the tumour is hormone receptor positive and whether human epidermal growth factor receptor 2 (HER2) is overexpressed. Here, we report a case of HER2 positive metastatic breast cancer on a woman in her late 30s, with remission for over 3 years under second-line treatment with ado-trastuzumab emtansine, with no significant toxicity and good tolerability. The timing to stop treatment under these circumstances presents a challenge and more data are needed to substantiate the decision to stop or maintain treatment in this small population.