Clinical Relevance of Tissue and Serum Human Epidermal Growth Factor Receptor 2 Expression in Patients With Esophageal Squamous Cell Carcinoma.

Background: Serum and tissue human epidermal growth factor receptor 2 (HER2) levels were evaluated in resected esophageal squamous cell carcinoma (SCC) specimens to assess the relationship between HER2 expression and long-term prognosis.

Methods: We included 95 patients who underwent esophagectomy for esophageal SCC. The serum HER2-extracellular domain (sHER2-ECD) levels were measured using an ELISA kit. A time-dependent receiver operating characteristics curve for censored survival outcomes was constructed to estimate the optimal cut-off value of sHER2-ECD (set at 4211 pg/mL). Immunohistochemical (IHC) staining was performed for HER2, and specimens were classified based on low (0 or 1+) or high HER2-IHC expression (2+ or 3+).

Results: Patients with low sHER2-ECD levels showed poorly differentiated tumors, nodal involvement, and larger tumor size more frequently compared to patients with high sHER2-ECD levels. There were no differences in clinicopathological features based on HER2-IHC expression. Between patients with high and low HER2-IHC expression, the former group showed significantly higher sHER2-ECD levels. Patients with high sHER2-ECD levels had significantly favorable relapse-free survival (RFS) and overall survival (OS) compared to those with low sHER2-ECD levels. Conversely, patients with high HER2-IHC expression had significantly poorer RFS than did patients with low HER2-IHC expression, although no difference was observed in OS. Additionally, patients with high sHER2-ECD levels and low HER2-IHC expression had the highest OS and RFS among the patients studied.

Conclusions: The correlation among sHER2-ECD levels, HER2-IHC expression, and prognosis was demonstrated. Prospective studies are required to validate the impact of serum and tissue HER2 expression in esophageal SCC prognosis.