ERBB2 status and benefit from adjuvant tamoxifen in ERalpha-positive postmenopausal breast carcinoma.

We examined the relation between ERBB2 gene expression (as determined by a real-time quantitative RT-PCR assay) and the response to adjuvant tamoxifen therapy in a well-defined cohort of 125 ERalpha-positive postmenopausal patients with breast cancer. Although ERBB2 overexpression was associated with shorter relapse-free survival in univariate analysis (P=0.00029), ERBB2 did not persist as an independent prognostic factor in multivariate analysis. Nevertheless, when we analyzed the ERBB2 mRNA level as a continuous variable, the higher the ERBB2RNA level, the poorer the outcome (P=0.00036). The results point to the need for a quantitative ERBB2 expression assay for use in future studies of ERBB2-based clinical management of breast cancer.