T-DM1 , which is a highly innovative but also expensive antiHER2 agent consisting in the coupling of the humanised monoclonal antibody trastuzumab with a cytotoxic agent (maytansine derivate) has shown an encouraging antitumor activity evaluated by Recist criteria (35% objective response rate, 44% stable disease, 18% progressive disease) in patients with advanced HER2 positive Breast Cancer pretreated with several cytotoxic drugs, trastuzumab and lapatinib.