Prognostic value of baseline serum HER2 extracellular domain level with a cut-off value of 15 ng/mL in patients with breast cancer: a systematic review and meta-analysis.

The extracellular domain (ECD) of human epidermal growth factor receptor-2 (HER2) in the blood is a promising biomarker of cancer prognosis and response to therapy, whereas the clinical prognostic role of serum HER2 ECD (sHER2 ECD) level in patients with BC remains controversial. Moreover, its cut-off value significantly varies. Thus, this meta-analysis aimed to quantify the prognostic impact of this biomarker with a specific cut-off value in patients with BC.