Diffuse Gastric and Esophagogastric Junction Cancer S-1 Trial

Inclusion Criteria:

Has given written Informed Consent.
Histologically confirmed, unresectable, metastatic diffuse gastric cancer including carcinoma of the gastro-esophageal junction.
No prior chemotherapy for gastric cancer except adjuvant and/or neo-adjuvant chemotherapy more than 12 months ago.
Life expectancy of at least 3 months.
Able to take medications orally.
Eastern Cooperative Oncology Group performance status 0 to 1.
Adequate organ function (bone marrow, kidney and liver).

Exclusion Criteria:

Certain type(s) of non-measurable lesion(s), if the only one(s).
Certain serious illness or medical condition(s).
Lost greater than or equal to 10% of body weight in the 3 months proceeding signing the Informed Consent Form.
Treatment with drugs interacting with S-1, 5-FU, or cisplatin.
Pregnant or lactating female.
Known hypersensitivity to fluoropyrimidines or cisplatin.

Other protocol-defined inclusion/exclusion criteria may apply.