Role of Herceptin in primary breast cancer: views from North America and Europe.

Current therapeutic strategies for primary breast cancer aim to provide improvements in outcome with minimal toxicity to the patient. However, annual relapse rates of up to 12 to 13% during the first 10 years after treatment are seen, and although toxicity has been reduced, it remains a problem in a patient population that is largely asymptomatic. Thus, there is a clear need for more effective therapies. Amplification/overexpression of the human epidermal growth factor receptor-2 (HER2) is an early event in the development of a significant proportion of breast tumors. This abnormality has been shown to have a detrimental effect on prognosis, may predict the outcome of therapies such as tamoxifen and anthracyclines, and provides a target for the novel therapy, Herceptin. Herceptin is effective and well tolerated in the metastatic setting, making it an ideal candidate for use in adjuvant breast cancer therapy. This has led to the design of a number of trials that aim to provide conclusive evidence as rapidly as possible that Herceptin is well tolerated and effective in the adjuvant setting while also addressing the question of which regimen provides greatest benefit. This review describes these trials and explains how differences in practice between North America and Europe have influenced trial design.