When Is a Tumor Marker Ready for Prime Time? A Case Study of c-erbB-2 as a Predictive Factor in Breast Cancer

Abstract

PURPOSE: c-erbB-2 (HER-2, c-neu) might play a role as a predictive factor in breast cancer. However, the clinical utility of the marker in this disease is still not established. We conducted a critical analysis of the literature, in which we reviewed the factors that contribute to the lack of acceptance of c-erbB-2 for clinical use and attempted to determine the predictive role of c-erbB-2 for response to specific therapies. METHODS: We conducted a MEDLINE literature search using the keywords c-erbB-2, HER2, neu, and breast cancer, reviewed the references included in each publication, and reviewed abstracts that have been reported in the 1997-2000 proceedings to the American Association of Cancer Research and American Society for Clinical Oncology annual meetings. RESULTS: The preclinical and clinical data reported to date suggest that amplification or overexpression of c-erbB-2 is a weak to moderate negative pure prognostic factor. c-erbB-2 seems to be a weak to moderate negative predictive factor for response to endocrine therapy. The marker is also a moderate negative predictive factor for response to alkylating agents and a moderate positive predictive factor for response to anthracyclines. The data regarding response to taxanes or radiotherapy are not sufficient to make recommendations regarding treatment decision making. Finally, c-erbB-2 is a strong predictive factor for response to trastuzumab. CONCLUSION: We conclude that, in the adjuvant setting, c-erbB-2 status should not be used to determine whether a woman should receive adjuvant systemic therapy (weak prognostic factor). In addition, c-erbB-2 status should not be used to determine whether a patient should receive endocrine therapy. When adjuvant chemotherapy is recommended, anthracycline-based therapy should be the preferred regimen for c-erbB-2–positive patients. However, when anthracyclines are contraindicated, alkylating agent–based therapy should not be withheld. To determine the true predictive role and strength of the marker for response to each therapy, prospective randomized clinical trials or formal meta-analyses are required.