The Current Evidence and Future Direction of Adjuvant Treatment for Gastric Cancer in the Era of Precision Medicine.

Although gastric cancer remains a significant global health burden, its treatment strategies vary across different geographical regions, leading to distinct guidelines. In Asia, particularly in Korea, D2 gastrectomy followed by adjuvant chemotherapy has been established as the standard treatment for stage II/III gastric cancer based on landmark clinical trials. However, this "one-size-fits-all" approach requires refinement as emerging evidence suggests heterogeneous outcomes even within the same stage. This review discusses the evolving landscape of adjuvant treatment in gastric cancer, emphasizing the transition towards precision medicine. Recent molecular characterization of gastric cancer has revealed distinct subtypes with varying prognoses and chemotherapy responses, exemplified by the favorable outcomes of microsatellite instability-high tumors without adjuvant chemotherapy. Additionally, clinical factors including sub-stages within stage II/III, patient performance status, comorbidities, and personal preferences should be considered in treatment decisions. The integration of these molecular and clinical factors, along with shared decision-making between physicians and patients, represents a crucial step toward personalized treatment approaches. Looking ahead, the field is poised for further evolution with the emergence of immune checkpoint inhibitors, growing evidence for neoadjuvant chemotherapy in selected cases, and the potential of circulating tumor DNA as a biomarker for minimal residual disease. This comprehensive approach to treatment decision-making, considering both tumor biology and patient factors, will be essential for realizing precision medicine in gastric cancer care.