DISEASE CHARACTERISTICS:

• Diagnosis of colorectal adenocarcinoma, defined by 1 of the following:

  • Prior or current histologically confirmed primary adenocarcinoma of colon or rectum with clinical or radiological evidence of advanced and/or metastatic disease
  • Histologically and cytologically confirmed metastatic adenocarcinoma with clinical and/or radiological evidence of colorectal primary tumor
• Unidimensionally measurable disease by RECIST criteria

• Inoperable metastatic or locoregional disease

  • Potentially resectable liver metastases allowed provided the following criteria are met:

    • Fewer than 4 unilobar liver metastases, each < 4 cm in size and without major vascular involvement
    • No combination chemotherapy allowed prior to the planned resection of operable liver metastases
• No brain metastases

PATIENT CHARACTERISTICS:

• WHO performance status 0-2
• Must be considered fit to undergo combination chemotherapy
• ANC ≥ 1,500/mm³
• Platelet count ≥ 100,000/mm³
• Serum bilirubin ≤ 1.25 times upper limit of normal (ULN)
• Alkaline phosphatase ≤ 5 times ULN
• AST or ALT ≤ 2.5 times ULN
• Creatinine clearance ≥ 50mL/min OR glomerular filtration rate ≥ 50 mL/min
• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective contraception
• No severe uncontrolled concurrent medical illness (including poorly controlled angina or myocardial infarction within the past 12 weeks) likely to interfere with protocol treatments
• No psychiatric or neurological condition that would preclude study compliance with oral medication or giving informed consent
• No partial or complete bowel obstruction
• No preexisting neuropathy > grade 1
• No prior or current malignant disease which, in the judgement of the treating investigator, is likely to interfere with COIN-B treatment or assessment of response
• No patients with known hypersensitivity reactions to any of the components of the study treatments
• No proven dihydropyrimidine dehydrogenase deficiency (DPD) or personal or family history of DPD

PRIOR CONCURRENT THERAPY:

• See Disease Characteristics
• No prior systemic palliative chemotherapy for metastatic disease
• No prior oxaliplatin
• More than 1 month since prior adjuvant chemotherapy comprising fluorouracil (with or without leucovorin calcium), capecitabine, or irinotecan hydrochloride
• More than 1 month since prior chemoradiotherapy comprising fluorouracil (with or without leucovorin calcium) or capecitabine for rectal cancer
• No ongoing requirement for contraindicated concurrent medication
• No concurrent enrollment in any type of study other than observational studies