PO141 SUCCESSFUL USE OF HER2 TARGETED AGENTS IN PATIENTS WITH HEAVILY PRETREATED HER2-NEGATIVE METASTATIC BREAST CANCER PRESENTING WITH ELEVATED SERUM LEVELS OF THE HER2 EXTRACELLULAR DOMAIN AND/OR HER2 OVEREXPRESSING CIRCULATING TUMOR CELLS. (November 2015) - Kurbacher, Christian Martin; Quade, Annegret; Kunstmann, Gerhard; Herz, Susanne; Kurbacher, Jutta Anna; Warm, Matthias R.