The expression of HER2 low in gastric and gastroesophageal junction adenocarcinoma

Gastric or gastroesophageal junction (G/GEJ) adenocarcinoma is the fifth most common malignancy and the third leading cause of cancer-related mortality worldwide. Adenocarcinoma is the most common type of gastric cancer. These cancers have poor prognosis and surgery is the only potentially curative approach. Neoadjuvant or adjuvant chemotherapy should be combined with surgery in locally advanced cases. 15-20% of gastric and GEJ carcinoma is associated with HER2 overexpression.

Human epidermal growth factor receptor 2 (HER2) is a member of epidermal growth factor receptor family which has tyrosine kinase activity and plays a role in cell proliferation and survival.Recently, trastuzumab deruxtecan (T-DXd)-an antibody drug conjugate (ADC) consisting of an anti-HER2 antibody with a cytotoxic topoisomerase I inhibitor demonstrated superior efficacy to standard cytotoxic chemotherapies in patients with HER2-positive G/GEJ adenocarcinoma and showed some efficacy in HER2 low carcinoma.

This study aims to assess the prevalence of HER2- low (HER2 1+ or 2+ without amplification) in gastroesophageal junction and gastric adenocarcinoma, and to evaluate its association with clinical and histopathological features.