Phase II Study of TS-1 Therapy and TS-1+PSK Therapy Against Advanced Gastric Carcinoma

Inclusion Criteria: * Patients with unresectable advanced gastric carcinoma and recurrent gastric carcinoma. * Patients who are 20 years old or older at the time of obtaining consent. * Patients who have not received prior treatment, including radiotherapy, chemotherapy and immunotherapy, before the start of treatment (however, patients are excluded when six months or more have passed since they received postoperative adjuvant chemotherapy.) * Patients who do not develop metachronous or simultaneous multi cancer. * Patients who do not show severe impairments in renal function, liver function and bone marrow function and who maintain the major organ functions which meet all requirements as described below (laboratory values are values measured before the start of protocol treatment and should be updated ones which are measured within two weeks before protocol treatment is started.) WBC counts: \>= 3,000 /mm3 and \< 12,000 /mm3 Neutrophil counts (ANC): \>= 1,500 /mm3 Platelet counts: \>= 100,000 /mm3 Amount of hemoglobin: \>= 8.0 g/dL Serum GOT and GPT: Less than 100 IU/L Serum total bilirubin: Less than 1.5 mg/dL Serum creatinine: Less than 1.5 mg/dL * Patients whose performance status scores are 0 to 2. * Patients who are judged that they can endure this treatment in a comprehensive manner and who have provided written informed consent to participate in this research. * Presence or absence of measurable lesion does not matter, but if there are measurable lesions in patients, the lesions should be confirmed within 28 days before the enrollment. Exclusion Criteria: * Patients with fresh blood in the digestive tract. * Patients with body fluids which require treatment. * Patients with infectious disease, intestinal paresis and ileus. * Patients with diarrhea (watery stool). * Female patients who are pregnant or want to become pregnant during this study or male patients who intend to make someone pregnant during this study. * Diabetic patients who are being treated with insulin or are poorly controlled. * Patients with ischemic heart disease which require treatment * Patients who are complicated with psychosis and judged that it is difficult for them to participate in this study. * Patients who continue to receive steroids. * Patients who have experienced serious drug allergy in the past. * Patients who are taking health foods including agaricus which are considered to have immunostimulating effects. * Patients judged to be inappropriate for this study by investigators and sub-investigators.