T-DM1 effects will be monitored by a combination of Next Generation Sequencing (NGS, tumor tissue) and Liquid Biopsy (LB, blood), as described below, to capture molecular events (gene aberrations, mainly mutations) associated with (or causative of) relapse as well as primary/adaptive resistance to HER2 blockade.~This study will prospectively monitor these events throughout the clinical history of the patients (archival tissues, blood collection, aimed biopsies). No investigational drugs will be administered.~This protocol is classified as interventional for two reasons:~dedicated, additional blood drawings (liquid biopsies)are collected in addition to the routine bloodtests being requested as per standard clinical practice;~the study involves occasional fine-needle biopsy on accessible (e.g. cutaneous) metastatic foci in selected patients to confirm their HER2 status, as per good medical practice.~These will represent an additional opportunity of targeted NGS.~Both blood (a) and tissues (b) will be obtained during T-DM1 treatment of enrolled patients at the participating Sites at the study specific timelines.
This is an open, interventional, non-pharmacological, prospective study. Patients will receive trastuzumab emtansine (T-DM1) at 3.6 mg/kg intravenously every 21 days, as per Summary of Product Characteristics (SmPC). This is a no-profit study.