Efficacy and Safety of the Combination of Trastuzumab Plus TUCAtinib Plus viNorelbine in Patients With HER2-positive Non-resectable Locally Advanced or Metastatic Breast Cancer

Breast cancer (BC) is the most common neoplasm in the world. In Spain, one in 8 women is diagnosed with BC. The human epidermal growth factor receptor 2 (HER2)-positive BC subtype (that represents around 20% of all BC) was associated with poor prognosis however, new therapeutic advances have significantly increased the cure rate of patients in early stages. In the metastatic setting, anti-HER2 targeted therapies have significantly improved overall survival (OS) with good quality of life, however there is still a substantial group of patients who die, and therefore additional drugs need to be investigated. Trastuzumab, an anti HER2 antibody has demonstrated, in combination with chemotherapy, an improvement of OS in early and metastatic stages. Tucatinib is an oral selective inhibitor of the HER2 receptor tyrosine kinase subunit. Its high affinity for this subunit causes fewer toxicities, such as rash and diarrhea, which are common with other anti-HER tyrosine kinase inhibitors (TKIs). Vinorelbine has been evaluated previously in combination with trastuzumab showing interesting results. This is a single country, multicenter, single arm phase II clinical trial with a safety run-in phase, to study the efficacy, safety and tolerability of the administration of tucatinib in combination with trastuzumab and vinorelbine in HER2-positive non-resectable locally advanced or metastatic breast cancer (MBC) with measurable disease.