Although trastuzumab-based regimens have improved both systemic control and overall survival in the patients with HER2-positive breast cancer, in some of these patients, tumor progression occurs despite trastuzumab treatment. New target therapies are searched for these patients. The most promising and, in terms of clinical use, the most developed is lapatinib, a small molecule, tyrosine-kinase inhibitor that targets not only HER2- but also HER1-receptor. It is already used for treating the HER2-positive metastatic breast cancer patients after failure of trastuzumab therapy, but its effectiveness in adjuvant therapy has not been proven yet. ALTTO (Adjuvant Lapatinib and/or Trastuzumab Treatment Optimization) is a randomized phase-three multi-center study of adjuvant lapatinib, trastuzumab, their sequence and their combination in the patients with HER2 positive primary breast cancer
