Duration of trastuzumab for HER2-positive breast cancer.

Several large randomised trials completed in the mid-2000s produced overwhelming evidence that the anti-HER2 monoclonal antibody trastuzumab, administered either concomitantly or sequentially with adjuvant chemotherapy for 12 months, increases the cure rate for women with HER2-positive operable breast cancer.1 One surprising aspect of this success story is that the choice of 12-month treatment duration was mostly as a result of a best guess, rather than on the basis of pre-existing evidence. Consequently, the optimum duration of treatment with adjuvant trastuzumab has been, and remains, unclear. In patients with metastatic disease, withholding trastuzumab in a responding patient almost always leads to disease progression. This observation would support administering trastuzumab for a longer period. Conversely, in women with operable breast cancer, two small studies suggested that when trastuzumab is administered concomitantly with chemotherapy for between 9 weeks and 6 months, the reduction in the risk of relapse is similar to longer treatment regimens.1 A shorter period of trastuzumab treatment would be an attractive option for several reasons, including reduced toxicity, inconvenience to patients, and costs. ..................................