Trastuzumab: new preparation. May help some patients with breast cancer, but too many unknowns

(1) In the absence of a reference treatment, patients with metastatic breast cancer qualifying for cytotoxic chemotherapy are generally treated with the doxorubicin + cyclophosphamide combination. (2) Trastuzumab, a monoclonal antibody directed against HER2 protein, has been granted marketing authorisation for the treatment of metastatic breast cancer in women with high HER2 protein levels, either as third-line monotherapy, or as first-line combination therapy with paclitaxel. (3) The clinical file only comprises two trials, the results of which are difficult to interpret. (4) In second- or third-line monotherapy, the only available trial (a non comparative study involving 222 patients) gave a median survival time of 13 months. For want of comparative data, there is no way of knowing if the clinical benefit and adverse effects profile of trastuzumab are better than those of other cytotoxic agents. (5) In first- or second-line treatment, there is only one unblinded comparative trial: it compared four groups receiving anthracycline + cyclophosphamide + trastuzumab; anthracycline + cyclophosphamide; paclitaxel + trastuzumab; or paclitaxel alone. The addition of trastuzumab appeared to extend the median survival time by 4-5 months. (6) The main known risks of trastuzumab therapy are cardiac reactions (the most severe) and flu-like syndromes (the most frequent, occurring in 40% of patients). (7) In the two available trials, a retrospective analysis suggested that the impact of trastuzumab was related to the amount of HER2 protein in the tumour. Unfortunately, HER2 assays are poorly standardised. Approximately one-quarter of patients appear to have high tumour HER2 protein contents. (8) At the time of writing (May 2001), the treatment of metastatic breast cancer is not modified by the advent of trastuzumab.