Uracil and Tegafur/Leucovorin (UFT/LV) Versus UFT/LV+ Polysaccharide-K (PSK) for Stage IIIa/IIIb Colorectal Cancer

Inclusion Criteria: * Patient with a histological diagnosis of primary colon or rectal cancer (adenocarcinoma) * Patient with histological stage IIIa or IIIb cancer (according to the Japanese Classification of Colorectal Cancer, 7th edition) * Patient who has undergone curative surgery with no residual cancer * Pretreatment criterion: patient who has not undergone preoperative cancer treatment (radiotherapy, chemotherapy or immunotherapy) * Patient who is at least 20 years and below 80 years of age * Patient with performance status (PS) of 0-1 (according to Eastern Cooperative Oncology Group, ECOG) * Restrictions of concomitant medications and therapies: except in the case of metastasis or recurrence, concomitant use of other chemotherapeutic and immunotherapeutic agents that may affect the results of this trial, and concomitant use of radiotherapy are prohibited in principle. * Organ function (laboratory data): patient who satisfies the following conditions or data of laboratory tests conducted within 2 weeks prior to start of trial * Gastrointestinal function: no diarrhea (watery stool) * White blood cell count: \> 4,000/mm3 * Platelet count: \> 100,000/mm3 * Serum GOT and GPT: \< 100 IU/L * Serum total bilirubin: \< 2.0 mg/dL * Serum creatinine: below the upper limit of facility normal range Exclusion Criteria: * Patient with residual cancer (R1 or R2) * Patient with anal canal lesion (P) or perianal skin lesion (E) * Patient with stricture and not capable of oral intake * Patient passing fresh blood from the gastrointestinal tract * Patient with retention of body cavity fluid necessitating treatment * Patient with infection, intestinal palsy or intestinal occlusion * Patient with active multiple cancers or patient who has less than 5 years of remission from a metachronous cancer (except carcinoma in situ and skin cancer) * Patient who is pregnant or wishes to become pregnant during this trial * Patient on continuous insulin treatment for diabetes or has poorly controlled diabetes * Patient with a history of ischemic heart disease and judged to have difficulties to participate in this trial * Patient with concurrent psychiatric disease or neurological symptoms and judged to have difficulties to participate in this trial * Patient on continuous steroid therapy * Patient with a history of serious drug allergy * Patient who is judged for other reasons by the investigator or doctor in charge to be inappropriate as a subject