Prognostic value of serum level of HER-2 extracellular domain (ECD) at diagnosis of HER-2 overexpressed primary breast cancer (BC)

Abstract

e11508 Background: Serum level of HER2 ECD is an adverse prognostic factor in HER2 over-expressed metastatic BC. We analyzed the prognostic value of serum level of HER2 ECD at the diagnostic of HER2 over-expressed primary BC. Methods: Patients with HER2 over-expressed primary BC treated with adjuvant trastuzumab in 2005 and 2006 were retrospectively analyzed. Serum level of HER2 ECD was assessed on frozen sera collected for CA15–3 measurement before initial treatment. Serum level of HER2 ECD was measured with an Elisa commercial kit (Oncogene Science, Cambridge, MA). The cut-off was 15μg/l as recommended. Results: Pre-treatment serum was available for 65 patients treated for non metastatic HER2 over-expressed BC. Seven patients (11%) had initially an elevated serum level of HER2 ECD (mean 25μg/l, range 15.1–38.9). After an average follow-up of 30 months, 4 patients (57%) out of the 7 with initially elevated serum level of HER2 ECD had a metastatic relapse of BC. In contrast, only 3 patients (5%) out of 58 with initially low serum level of HER2 ECD experienced relapse (p=0.004). Median of serum level of HER2 ECD was 17μg/l in patients who experienced relapse during follow-up whereas it was 8.4μg/l in patients who remained relapse-free (p=0.03). Univariate analysis showed that only elevated serum level of HER2 ECD and absence of hormone receptors expression were linked with metastatic relapse (p=0.0004 and p=0.02, respectively). Multivariate analysis showed that elevated serum level of HER2 ECD and absence of hormone receptors expression were linked with metastatic relapse (p=0.02 and p=0.04, respectively). Survival curves showed also that elevated serum level of HER2 ECD was related with a worse disease-free survival (p=0.0004). Conclusions: In this small series, elevated serum level of HER2 ECD was an adverse prognostic factor for HER2 over- expressed non metastatic primary BC. It was also a predictive factor for early failure of adjuvant treatment with trastuzumab. No significant financial relationships to disclose.