S-1 is an effective adjuvant treatment for East Asian patients who have undergone a D2 dissection for locally advanced gastric cancer. (ClinicalTrials.gov number, NCT00152217 [ClinicalTrials.gov].).

On the basis of 5-year follow-up data, postoperative adjuvant therapy with S-1 was confirmed to improve overall survival and relapse-free survival in patients with stage II or III gastric cancer who had undergone D2 gastrectomy.

Recent developments in treatment modalities for gastric cancer have allowed the selection of a variety of treatments, and this has resulted in some confusion in daily practice. The Japan Gastric Cancer Association issued the first edition of Gastric cancer treatment guidelines in March, 2001 to provide a common basis of understanding of the extent of disease and selection of proper treatment among doctors, patients, and their families.