Although a multidisciplinary treatment (MDT) for GC patients has been developed, trastuzumab has been approved for human epidermal growth factor receptor 2 (HER2)-positive metastatic GC patients, and immunocheckpoint inhibitors have been approved for the third-line treatment of metastatic GC patients, the prognosis of most patients with metastatic GC is far from satisfactory (1–5). The gene discussed is ERBB2; the disease is gastric cancer.