The purpose of this study is to evaluate the effectiveness and safety of S-1 plus Leucovorin (1 week on and 1 week off) as first-line treatment for patients with metastatic and recurrent gastric cancer.

Patients enrolled in this study were orally treated with S-1 in doses of 40 mg (body surface area (BSA)<1.25 m2), 50 mg (1.25≤BSA<1.50 m2) and 60 mg (BSA≥1.50 m2) b.i.d. on days 1-7 in combination with LV given simultaneously at a fixed dose of 25 mg b.i.d. on days 1-7, followed by a 7 day rest. Treatment courses were repeated every 2 weeks. Treatment was continued until progressive disease (PD), unacceptable toxicity or patient refusal.

Inclusion Criteria:

• histologically confirmed metastatic or recurrent gastric cancer
• with at least one measurable lesion by RECIST criteria
• an age of ≥ 18
• adequate oral intake
• no previous radiotherapy, immunotherapy, biotherapy, hormonotherapy and chemotherapy within 5 years (adjuvant chemotherapy without S-1 was allowed if finished 6 months before enrollment)
• an Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1
• adequate bone marrow function, hepatic function and renal functions

Exclusion Criteria:

• a history of hypersensitivity to S-1 or LV, usage of drugs interacting with S-1
• serious concomitant conditions (severe heart disease, pulmonary fibrosis, intestinal obstruction, enteroplegia, renal failure, liver failure, pre-existing sensory neuropathy ≥ grade 2, uncontrolled infections, psychogenic disorders, human immunodeficiency virus infection, severe diarrhea, nausea, or vomiting, severe ascites or pleural effusion, etc.)
• extensive bone metastasis, brain metastasis or meningeal metastasis
• another synchronous cancer
• surgery within 3 weeks before enrollment
• participating in other clinical studies
• women who were or to be pregnant, nursing infants, and men who were to conceive children