The predictive value of HER2 in breast cancer

Measurement of molecular markers predictive of response to therapy should e nable more selective and effective utilization of anticancer agents. The pr edictive value of HER2 remains a complex and inconclusive subject. In metas tatic breast cancer, HER2-positive, ER-positive patients can show responses to endocrine treatment, but experience shorter time to progression and sur vival than HER2-negative patients. In the adjuvant setting, weak, retrospec tive evidence suggests that tamoxifen is potentially harmful in HER2-positi ve patients and that there is no benefit from prolonged tamoxifen therapy. It has not yet been demonstrated conclusively that HER2 positivity increase s resistance to adjuvant cyclophosphamide, methotrexate, 5-FU (CMF), but th ere are indications that HER2-positive patients benefit more from adequatel y dosed anthracyclines than from CMF. The greatest value of HER2 as a predi ctive marker lies in the prediction of response to therapies that target HE R2, such as Herceptin (R). Patients with strongly HER2-positive breast canc er derive significant clinical benefit from single-agent and combined Herce ptin therapy. HER2 testing has become an integral part of the optimal manag ement of the breast cancer patient. Best current practice in adjuvant breas t cancer therapy based on the current knowledge of the potential predictive power of HER2 constitutes not denying tamoxifen to HER2-positive, ER-posit ive patients or CMF to HER2-positive patients. Outside of clinical trials, adequately dosed anthracycline-based chemotherapy is the current preferred adjuvant treatment option for HER2-positive patients. Copyright (C) 2001 S. Karger AG, Basel.