Adjuvant Chemotherapy for the Treatment of HER2-Positive Early Breast Cancer

HER2-positive breast cancer is characterized by high chemosensitivity. Anthracycline-based chemotherapy is recognized as a very effective adjuvant treatment in HER2-positive disease. One of the possible explanations is the co-amplification of TOPO II-alpha and HER2. However, recent data seem to demonstrate that HER2 and TOPO II-alpha seem to be less predictive of anthracycline-based chemotherapy efficacy than chromosome 17 polysomy. Chromosome 17 polysomy is present in 21-40% of breast cancer and for this reason benefit of anthracycline-based chemotherapy seems to be not restricted only to HER2-positive disease. Trastuzumab added to chemotherapy administered for one year is associated with improvement in disease-free survival and sometimes in overall survival compared to chemotherapy alone. Efficacy of trastuzumab in the adjuvant setting seems to be increased if administered concomitantly with chemotherapy instead of sequentially. However, the interpretation of longer follow-up results is difficult because of a large crossover from the control arm to trastuzumab.