Inclusion Criteria

DISEASE CHARACTERISTICS: Histologically proven metastatic, advanced, or locally recurrent
fluorouracil (5-FU) refractory adenocarcinoma of the colon or rectum Progression of
disease within 6 months of receiving adjuvant 5-FU based chemotherapy OR Progression of
disease during or following completion of 5-FU based chemotherapy for metastatic disease
No more than 1 failure with a 5-FU regimen for recurrent, advanced, or metastatic disease
Failure on 5-FU adjuvant therapy must accompany failure on 5-FU therapy for metastatic
disease Bidimensionally measurable disease CNS metastases allowed only with measurable
disease in other sites Prior treatment for CNS metastases required

PATIENT CHARACTERISTICS: Age: 18 and over Performance status: ECOG 0-2 Life expectancy: At
least 12 weeks Hematopoietic: WBC at least 3500/mm3 Absolute neutrophil count at least
1500/mm3 Platelet count at least 100,000/mm3 Hepatic: Bilirubin no greater than 1.5 mg/dL
AST and ALT no greater than 3 times upper limit of normal Renal: Creatinine no greater
than 1.5 mg/dL OR Creatinine clearance at least 60 mL/min Other: No other significant,
uncontrolled underlying medical or psychiatric condition No serious active infection Not
pregnant or nursing Negative pregnancy test Fertile patients must use effective
contraception Neurologically stable No other prior malignancy within past 5 years except
curatively treated nonmelanomatous skin cancer

PRIOR CONCURRENT THERAPY: Biologic therapy: No concurrent immunotherapy Chemotherapy: See
Disease Characteristics Prior adjuvant fluorouracil (5-FU) allowed No more than 2 prior
5-FU regimens (no more than 1 for recurrent or metastatic disease) No other concurrent
chemotherapy Endocrine therapy: No concurrent hormonal therapy (except contraceptives or
replacement steroids) No concurrent IV steroids Radiotherapy: Prior radiotherapy allowed
if measurable disease outside radiation port At least 4 weeks since prior radiotherapy and
recovered No concurrent radiotherapy Surgery: Not specified Other: No concurrent
anticonvulsant therapy No other concurrent experimental medications