<qa>  What is the recommended phase II dose of vinorelbine?This is a Phase III, single arm, open-label clinical trial designed to establish the recommended phase II dose RP2D of vinorelbine with a fixed dose of trastuzumab emtansine. The study will also evaluate the safety and efficacy of the RP2D in patients with human epidermal growth factor receptor 2 HER2-positive metastatic, locally advanced, or unresectable breast cancer. The study will be opened to accrual at the University of Miami Sylvester Comprehensive Cancer Center SCCC main campus and constituent satellite sites, Deerfield Beach and Plantation. 