DISEASE CHARACTERISTICS: Histologically or cytologically confirmed unresectable metastatic or recurrent adenocarcinoma of the colon or rectum No brain metastases unless previously treated, asymptomatic, on stable dose of decadron, and CT/MRI scan demonstrates no evidence of edema Phase I: Measurable or evaluable disease Phase II: Measurable disease Evidence of +1 bcl-2 expression on immunohistochemical staining in pathologic material

PATIENT CHARACTERISTICS: Age: 18 and over Performance status: ECOG 0-2 Life expectancy: At least 12 weeks Hematopoietic: Platelet count at least 100,000/mm3 Hemoglobin at least 9.0 g/dL Absolute granulocyte count at least 1,500/mm3 Hepatic: Bilirubin no greater than 1.5 mg/dL AST/ALT no greater than 3 times upper limit of normal (ULN) (5 times ULN if liver metastases) PT/PTT normal Renal: Creatinine no greater than 1.5 mg/dL Other: Not pregnant or nursing Negative pregnancy test Fertile patients must use effective contraception No active infection No serious concurrent systemic disorders that would preclude study treatment

PRIOR CONCURRENT THERAPY: Biologic therapy: No concurrent immunotherapy Chemotherapy: At least 4 weeks since prior chemotherapy (6 weeks for nitrosoureas and mitomycin) and recovered No other concurrent chemotherapy Phase I: At least 4 weeks since prior irinotecan and recovered Phase II: No more than 2 prior fluorouracil-based regimens for metastatic disease No prior irinotecan Endocrine therapy: See Disease Characteristics No concurrent anticancer hormonal therapy Radiotherapy: No concurrent radiotherapy Surgery: See Disease Characteristics Other: No other concurrent experimental medications