DISEASE CHARACTERISTICS:

• Histologically confirmed adenocarcinoma of the colon or rectum

  • Progressive locally advanced or metastatic disease
• Received 1 prior irinotecan- or oxaliplatin-containing regimen

• At least 1 measurable lesion

  • Target lesion must be outside field of prior radiotherapy
• No symptomatic brain metastases

PATIENT CHARACTERISTICS:

Age

• 18 and over

Performance status

• ECOG 0-2

Life expectancy

• At least 3 months

Hematopoietic

• Absolute neutrophil count ≥ 1,500/mm^3
• Platelet count ≥ 100,000/mm^3

Hepatic

• ALT and AST ≤ 2.5 times upper limit of normal (ULN) (5 times ULN if liver metastases are present)
• Bilirubin ≤ 1.5 times ULN

Renal

• Creatinine ≤ 1.5 times ULN

Gastrointestinal

• No difficulty with swallowing
• No malabsorption
• No diarrhea (excess of 2-3 stools/day above normal frequency) within the past month
• No history of chronic diarrhea

Other

• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective contraception
• HIV negative
• No concurrent serious infection
• No other concurrent severe or uncontrolled underlying medical condition that would preclude study participation
• No neuropathy ≥ grade 2
• No history of any severe or life-threatening hypersensitivity reaction
• No psychiatric disorder that would preclude study compliance
• No other malignancy within the past 2 years except nonmelanoma skin cancer or carcinoma in situ of the cervix

PRIOR CONCURRENT THERAPY:

Biologic therapy

• No concurrent biologic therapy

Chemotherapy

• See Disease Characteristics
• At least 4 weeks since prior myelosuppressive chemotherapy and recovered
• No other concurrent chemotherapy

Endocrine therapy

• Not specified

Radiotherapy

• See Disease Characteristics
• At least 4 weeks since prior radiotherapy and recovered

• No concurrent radiotherapy

  • Localized radiotherapy to non-indicator lesions for pain relief allowed provided other methods of pain control are ineffective

Surgery

• At least 4 weeks since prior major surgery and recovered
• No prior major surgery in the stomach or small intestine

Other

• More than 28 days since prior investigational agents (including analgesics and/or antiemetics)
• No other concurrent anticancer therapy
• No other concurrent cytotoxic therapy
• No concurrent grapefruit products