S-1 is an effective drug in gastric cancer (GC) for palliative chemotherapy in Eastern and Western patients. Recently, S-1 has been also reported to be an effective adjuvant therapy for GC patients who received D2 surgery in Eastern Asian patients.

Recently, the development of lacrimal drainage obstruction (LDO) caused by S-1 has been reported from some case and small-sized studies. The incidence of developing LDO has been estimated to about 15~20% of patients receiving S-1 therapy in some retrospective studies. However, there is no prospective report on the incidence of LDO in patients receiving S-1 chemotherapy. Moreover, the mechanism of developing S-1-induced LDO has not been systemically studied until now. Suggested mechanism of LDO involves direct secretion of S-1 into the tear.

Therefore, this study was initiated to prospectively investigate the incidence of LDO in GC patients receiving adjuvant S-1 chemotherapy. In addition, the correlation between the development of LDO and the concentration of S-1 (or its metabolites) in tear and plasma will be explored. These results will help clinicians identify patients who are at high risk of developing S-1-associated LDO.

Inclusion Criteria:

• Patients who received curative (R0) surgery for GC
• Patients receiving adjuvant S-1 chemotherapy
• Patients with adequate major organ functions for chemotherapy
• Patient who have taken S-1 at least 7 days (for blood and tear sampling)

Exclusion Criteria:

• Patients who are not candidate for adjuvant S-1 chemotherapy
• Patients with previous history of LDO
• Patients with other opthalmologic disease who are not appropriate to be included in this study (i.e., patients using eyedrop medication; patients with dry eye whose tears cannot be sampled)

Patients receiving S-1 as an adjuvant chemotherapy after radial surgery (D2 dissection) for GC