T-DM1 as a New Treatment Option for Patients with Metastatic HER2-positive Breast Cancer in Clinical Practice.

AIM To compare results of trastuzumab-emtansine (T-DM1) treatment in our clinical practice with data from phase III clinical trials. PATIENTS AND METHODS A retrospective chart review of all 23 patients with metastatic human epidermal growth factor receptor 2 (HER2)-positive breast cancer who were started on T-DM1 until April 2014 was performed. RESULTS Four patients (17.4%) received T-DM1 as first-line, three (13.0%) as second-line, six (26.0%) as third-line, and 10 (43.5%) as fifth- or further-line therapy. Overall, the response rate (ORR) was 26.0%, disease control rate 78.3% and median progression-free survival (PFS) 8.4 months. The only toxicities of grade 3 or more were fatigue (21.7%), thrombocytopenia (4.3%) and elevation of liver enzymes (8.7%). ORR and PFS were similar to the TH3RESA and EMILIA trials. Compared to the EMILIA study, we recorded higher rates of newly-diagnosed cerebral metastasis and cerebral progression in patients with stable peripheral metastases. CONCLUSION T-DM1 is effective and well-tolerated even in intensively pre-treated patients.