Meaningful interpretation of serum HER2 ECD levels requires clear patient clinical background, and serves several functions in the efficient management of breast cancer patients

Background: This study was initiated to evaluate the clinical significant of HER2 extracellular domain (ECD) in the real-time management of breast cancer patients. Methods: Five -hundred forty-six eligible breast cancer patients were divided according to their clinical background. The correlation between ECD, tissue HER2, and clinical outcome of the patients were analyzed. Results: Receiver operating characteristic analysis revealed that ECD measured before receiving neoadjuvant therapy yielded the highest area under the curve (0.9185; P < 0.0001), indicating that ECD and tissue HER2 levels are consistent in untreated tumor -bearing patients. At cut-off of 15.0 ng/ml, the prognostic value of ECD was demonstrated using univariate (HR = 1.664, P < 0.0001) and multivariate (HR = 1.547, P = 0.011) Cox regression analysis. Kaplan -Meier survival curves revealed that patients with elevated ECD had shorter progression free survival (PFS) (4.0 vs. 6.1 months, P < 0.0001). Elevated ECD was also an adverse predictor for PFS in response to anti-HER2 therapy (43 vs. 10.2 months, P = 0.0155). In contrast, L"20%, decreased ECD was associated with longer PFS in patients who received anti-HER2 therapy (10.9 vs. 2.4 months, P = 0.0164) and overall (10.7 vs. 2.8 months, P = 0.0034). Conclusions: A patient's clinical history can help determine whether ECD could provide added value for breast cancer management. (C) 2016 Elsevier B.V. All rights reserved.