Trastuzumab (Herceptin (R)): Monoclonal antibody in the treatment of HER2/neu-overexpressing breast cancer in the metastatic and (neo)adjuvant situation

Trastuzumab (Herceptin (R)) is a humanized monoclonal antibody that
specifically targets HER2/neu (human epidermal growth factor
receptor-2) breast cancer cells, which are overexpressed in about
25-30% of breast carcinomas. After phase I and II trials, several
phase III studies of trastuzumab alone or in combination with
various chemotherapies were conducted. Patients with HER2/neu
overexpression levels of 3+ determined by immunohistochemical assay
or gene amplification (fluorescence in situ hybridization) derive
most clinical benefit from trastuzumab. Taking into consideration
efficacy and side effect profile, the combination of trastuzumab
and paclitaxel showed an improvement of all clinical parameters,
including overall survival, for the first time in the history of
palliative breast cancer therapy. The application of trastuzumab
has meanwhile become an established part of systemic therapy of
metastastic breast cancer, and excellent data of its application in
the adjuvant setting now exist (NSABP-B31, NCCTG-N9831, HERA), with
significantly better relapse-free survival in the treatment arms
with trastuzumab. Ongoing trials investigate the role of
trastuzumab in the neoadjuvant setting. Trastuzumab is generally
well tolerated. Cardiotoxicity is the main concern, thus monitoring
of cardiac function is recommended.