Inclusion Criteria:

1. Histologically confirmed gastric adenocarcinoma with unresectable metastatic or
recurrent disease

2. Lesions confirmed on imaging within 28 days before registration (not required
measurable lesions as defined in RECIST version 1.1)

3. No previous chemotherapy or radiotherapy. However, adjuvant chemotherapy is allowed
the case of more than 6 months from the end of adjuvant chemotherapy

4. ECOG Performance Status of 0 to 2

5. Life expectancy of at least 3 months after registration

6. Written informed consent

7. Age of 20 to 74 years with either gender

8. Adequate Major organ functions within 14 days before registration

Exclusion Criteria:

1. Positive HER2 status

2. Previous history of fluoropyrimidines therapy within 6 months prior to registration

3. Previous treatment with platinum agents

4. Previous history of serious hypersensitivity to fluoropyrimidines or platinum agents

5. Previous history of adverse reactions suggestive of dihydropyrimidine dehydrogenase
(DPD) deficiency

6. More than one cancer at the same time or more than one cancer at different times
separated by a 5-year disease-free interval. However, multiple active cancers do not
include carcinoma in situ or skin cancer which is determined to have been cured as a
result of treatment.

7. Obvious infection or inflammation (pyrexia ≥ 38.0˚C)

8. Active hepatitis

9. Heart disease that is serious or requires hospitalization, or history of such disease
within past year

10. Having complication that is serious or requires hospitalization (intestinal
paralysis, intestinal obstruction, interstitial pneumonia or pulmonary fibrosis,
poorly controlled diabetes mellitus, renal failure, liver disorders, or hepatic
cirrhosis)

11. Being treated or in need of treatment with flucytosine, phenytoin or warfarin
potassium

12. Chronic diarrhea (watery stool or ≥4 times/day)

13. Active gastrointestinal bleeding

14. Body cavity fluids requiring drainage or other treatment

15. Clinical suspicion or previous history of metastasis to brain or meninges

16. Women who are pregnant, breastfeeding, or potentially (hoping to become) pregnant

17. Unwillingness to practice contraception

18. Poor oral intake

19. Psychiatric disorders which are being or may need to be treated with psychotropics

20. Otherwise determined by investigators or site principal investigators to be
unsuitable for participation in study