S-1 has been also shown to be an effective drug for palliative chemotherapy in Eastern and Western GC patients. Recently, some case and small-sized studies have been reported on lacrimal drainage obstruction(LDO)caused by S-1.Suggested mechanism of LDO involves direct secretion of S-1 into the tear; thus the concentration of S-1 metabolite in tear is expected to be high in patients who developed LDO than in patients without LDO. We investigate the concentration of S-1 and its metabolites in tear and plasma and find out its correlation with side effects such as LDO. These results will also help us identify patients who are at high risk of developing S-1-associated side effects.

1. S-1 metabolites concentration in plasma

   1. factors affecting plasma concentration

      • surgery subtype
      • serum creatinine

   2. systemic adverse effects of S-1 and its correlation with plasma S-1 metabolites concentration

      • enteritis
      • fatigue

2. S-1 metabolites concentration in tears

   1. correlation of tear concentration with plasma concentration
   2. lacrimal drainage obstruction caused by S-1 administration, and its correlation with tear S-1 metabolites concentration
   3. lacrimal drainage obstruction caused by S-1 administration, and its correlation with plasma S-1 metabolites concentration

Inclusion Criteria:

• Patients who received radical surgery for gastric cancer
• Patients who receiving S-1 adjuvant chemotherapy
• Patients who administrated S-1 for more than 7 days

Exclusion Criteria:

• who using eyedrop medication
• who has dry eye that tear cannot be sampled

Patients who receiving S-1 as an adjuvant chemotherapy after radial surgery for gastric cancer