HER2 overexpression occurs in 25% of breast cancers and seems to correlate
with poor prognosis. HER2 overexpression may predict tamoxifen failure and
different response rates to chemotherapeutic agents such as the! taxanes an
d anthracyclines. The detection of HER2 and its overexpression is performed
using fluorescent in situ hybridisation (FISH) and/or immunohistochemistry
(IHC).
Trastuzumab [Herceptin (H)] is a humanised IgG monoclonal antibody specific
for the growth factor receptor HER2. Pre-clinical trials using monoclonal
antibodies have shown inhibition of breast tumour growth in athymic nude mi
ce. Phase II and III clinical trials have evaluated the efficacy and safety
of Herceptin in women with metastatic breast cancer in combination with ot
her agents and as a single agent. Currently, Trastuzumab and paclitaxel is
the only combination indicated for the treatment of patients with metastati
c breast cancer whose tumours overexpress HER2. It is also indicated as a s
ingle agent in women with HER2-overexpressing metastatic breast cancer that
has progressed after previous chemotherapy. Herceptin is a well-tolerated
drug and the side-effects that are commonly seen with chemotherapy, such as
neutropenia, alopecia and mucositis, are rarely observed.
The main risk factors for cardiotoxicity are concurrent or previous anthrac
ycline exposure The potential role of Herceptin in the adjuvant setting is
currently being evaluated.