The course of serum HER-2/neu levels as an independent prognostic factor for survival in metastatic breast cancer

The purpose of this study was to determine the impact of serum HER-2/neu level dynamics during the course of disease and treatment on the prognosis of patients with metastatic breast cancer. Two thousand and thirty-eight serum samples collected sequentially after disease relapse in 286 patients with metastatic breast cancer were measured by Bayer Immuno 1™ assay retrospectively for serum HER-2/neu (cut-off level 15 ng/ml). One hundred and five patients (37%) presented with serum HER-2/neu continuously ≤15 ng/ml after disease recurrence, 71 (25%) had continuously elevated levels and 110 patients (38%) had both non-elevated and elevated values in the course of metastatic breast cancer. Patients with continuously elevated serum HER-2/neu levels had a significantly poorer survival after disease recurrence compared to patients with continuously or temporarily non-elevated serum HER-2/neu values (log-rank test: p<0.001). Including the number of palliative antitumor therapies and therapy response in Cox regression analysis, serum HER-2/neu dynamics revealed to be an independent prognostic factor for survival. In conclusion, 63% of 286 patients with metastatic breast cancer demonstrated either continuously or temporarily elevated serum HER-2/neu levels. Decrease of elevated serum HER-2/neu to levels ≤15 ng/ml and levels continuously ≤15 ng/ml during the course of disease correlated significantly with longer survival.