Gastric cancer (GC) is a molecularly heterogeneous disease. Its molecular background, epidemiology, and standard of care are quite different between Eastern and Western countries. Many efforts have been made in developing more effective surgeries and adjuvant
chemotherapies for resectable GC in each region. Recently, an intensive combination of
cytotoxic agents has been established as a new standard of adjuvant treatment. Meanwhile, palliative
chemotherapy is a uniform standard treatment for unresectable GC worldwide. Recently, one of the most remarkable advances in
therapy for unresectable GC has been the approval of
immune checkpoint inhibitors (ICIs). The use of ICIs as frontline treatment is currently being investigated. In addition, novel combinations of ICIs and targeted drugs are being evaluated in clinical trials. Despite these advances, the complex biology of GC has resulted in the failure of targeted
therapies, with the exceptions of HER2-targeted
trastuzumab and VEGFR2-targeted
ramucirumab. GC harbors many redundant oncogenic pathways, and small subsets of
tumors are driven by different specific pathways. Therefore, a combination strategy simultaneously inhibiting several pathways and/or stricter patient selection for better response to targeted drugs are needed to improve clinical outcomes in this field.