Combination Chemotherapy After Surgery in Treating Patients With High-Risk Stage II or Stage III Colorectal Cancer

DISEASE CHARACTERISTICS:

* Diagnosis of colorectal cancer meeting 1 of the following criteria:

  * High-risk stage IIB disease, defined as T4 disease, perforation, obstruction, \< 10 nodes examined, poorly differentiated histology, extramural venous invasion, or extramural lymphatic invasion
  * Fully resected stage III disease
* Patients with rectal cancer must meet the following criteria:

  * Underwent prior total mesorectal excision surgery with negative resection (R0) margins
  * No prior pre-operative or scheduled post-operative combined chemotherapy and radiotherapy
* No evidence of residual or metastatic disease
* Deemed suitable for adjuvant chemotherapy

PATIENT CHARACTERISTICS:

* WHO performance status 0-1
* Life expectancy \> 5 years with reference to noncancer-related diseases
* ANC ≥ 1,500/mm³
* Platelet count ≥ 100,000/mm³
* Hemoglobin ≥ 9 g/dL
* AST and ALT ≤ 2.5 times upper limit of normal
* Carcinoembryonic antigen (CEA) levels normal
* Glomerular filtration rate ≥ 30 mL/min (no moderate or severe renal impairment)
* Not pregnant or nursing
* Negative pregnancy test
* Fertile patients must effective contraception
* More than 12 months since prior and no active clinically significant cardiovascular disease, including any of the following:

  * Cerebrovascular accident
  * Myocardial infarction
  * Unstable angina
  * New York Heart Association class II-IV congestive heart failure
  * Serious cardiac arrhythmia requiring medication
  * Uncontrolled hypertension (i.e., blood pressure \> 150/100 mm Hg)
* Disease-free interval of ≥ 5 years for previous malignancy other than adequately treated in situ carcinoma of the uterine cervix or basal cell or squamous cell carcinoma of the skin
* No known or suspected dihydropyrimidine dehydrogenase deficiency

PRIOR CONCURRENT THERAPY:

* See Disease Characteristics
* No more than 10 weeks since prior surgery and recovered
* No prior chemotherapy (except in patients randomized after 12 weeks of adjuvant therapy)
* No prior abdomino-pelvic radiotherapy, with the exception of short-course pre-operative radiotherapy for rectal cancer
* No concurrent brivudine or sorivudine for patients taking capecitabine