HER2 status: a statistician's view.

The human epidermal growth factor receptor-2 (HER2) has been investigated as a prognostic and predictive factor in breast cancer. The studies undertaken have included retrospective subset analyses and this had led to problems with bias such that only marginal statistical significance can be given to the results obtained. Overall, the majority of studies have found that a HER2-positive status may predict a poor patient outcome. although some studies have contradicted this finding. As a predictor of response to treatment, the results on the value of HER2 status are less well defined. Many studies suggest that a HER2-positive status correlates with resistance to hormonal therapy. Furthermore, a number of studies have found that a HER2-positive status is associated with a relative resistance to CMF (cyclophosphamide. methotrexate, 5-fluorouracil) and chemosensitivity to anthracycline-based therapies. However, there are enough discrepancies between studies for the predictive value of HER2 status to be unproven at the present time. Large, well-defined and accurately reported prospective studies are required to determine with any statistical clarity the value of HER2 status as a prognostic or predictive factor in breast cancer. In the meantime, no therapeutic option should be overlooked based solely on the HER2 status of a patient.