Since it is not uncertain about efficacy of combination therapy with PSK and TS-1 in gastric cancer, in this study, we compare efficacy and safety of postoperative adjuvant therapy using TS-1 or TS-1+PSK in the stage II or III gastric cancer patients.

TS-1 is an oral anticancer drug approved in Japan consisting of tegafur (a pro-drug of fluorouracil, 5-FU), gimeracil and oteracil potassium. The response rate of TS-1 in the untreated advanced gastric cancer patients was 44.6% in the late phase II study. In 2007, efficacy of the adjuvant therapy using TS-1 in the resected gastric cancer patients was demonstrated by ACTS-GC study group conducted in Japan. PSK is an oral anticancer drug approved in Japan consisting of protein-bound polysaccharide extracted from mycelium of Trametes (Coriolus) versicolor, a kind of mushroom. Even though survival benefit by PSK in combination with adjuvant chemotherapy using 5-FU or tegafur in the postoperative gastric cancer patients was already demonstrated, it is not uncertain about efficacy of combination therapy with PSK and TS-1 in gastric cancer. In this study, we compare efficacy and safety of postoperative adjuvant therapy using TS-1 or TS-1+PSK in the stage II or III gastric cancer patients.

Inclusion Criteria:

• Patient who is pathologically confirmed as gastric cancer

• Patient who has received surgery with D2 or more lymph node dissection and whose final curability of surgical resection is grade A or B

• Patient whose final stage is II (except for T1), IIIA, or IIIB

• Patient without liver, peritoneal and distant metastasis, and who is negative in peritoneal cytological diagnosis

• Patient whose age at the registration is ranging between 20 and 80 years old

• Patient who has not received any preoperative therapy including radiotherapy, chemotherapy and immunotherapy

• Patient who has received surgery for gastric cancer within six weeks before the registration, and is judged to be capable of oral administration

• Patient who has no serious concurrent complications, and satisfies the following criteria

  • White blood cell count: > LLN or > 4,000 /mm3
  • Platelet count: > 100,000 /mm3
  • Serum total bilirubin: < 1.5 mg/dL
  • Serum AST (GOT), ALT (GPT): < 2.5 * ULN
  • Serum creatinine: < ULN

• Patient who has received an explanation of this study by assent documents, and has given written informed consent to participate in this study

Exclusion Criteria:

• Patient with metachronous or synchronous multicancer
• Patient who contraindicates to TS-1
• Patient who requires continuous use of flucytosine, phenytoin or warfarin potassium
• Patient who has experienced serious drug allergy over grade 3 in the past
• Patient with serious complications including paralysis of intestine, ileus, interstitial pneumonitis, fibroid lung, uncontrollable diabetes mellitus, heart insufficiency, renal insufficiency or hepatic insufficiency
• Patient with diarrhea (watery stool)
• Patient who is pregnant or in lactation, or wish to become pregnant during this study
• Male patient who intends to make someone pregnant during this study
• Patient with HIV positive
• Patient who is judged to be inappropriate as subject to this study by the principal investigator or the doctors in charge