Nitrocamptothecin in Treating Patients With Advanced or Recurrent Colorectal Cancer

DISEASE CHARACTERISTICS: Histologically or cytologically proven colorectal cancer with failure or relapse after at least 1 prior fluorouracil based chemotherapy regimen for advanced disease OR metastatic disease within 6 months after completion of adjuvant therapy No more than 1 prior fluorouracil based chemotherapy regimen for metastatic disease Prior oral fluorouracil or combinations of other drugs with fluorouracil allowed Prior adjuvant therapy with fluorouracil allowed and not counted as 1 regimen if given more than 1 year prior to study At least 1 bidimensionally measurable indicator lesion that has not been irradiated and has the following minimum dimensions: Skin nodule or superficial lymph node: 2 x 2 cm Lung lesion surrounded by aerated lung: 1 x 1 cm by chest x-ray or at least 2 cm in 1 dimension by CT scan Liver lesion, soft tissue mass, or lymph node: at least 2 cm in 1 dimension by CT scan or sonogram PATIENT CHARACTERISTICS: Age: Not specified Performance status: ECOG 0-2 Life expectancy: At least 8 weeks Hematopoietic: Granulocyte count greater than 1,500/mm3 Hemoglobin greater than 10 g/dL Platelet count greater than 100,000/mm3 Hepatic: SGOT and SGPT no greater than 3 times normal (no greater than 5 times normal if liver tumor present) Bilirubin no greater than 2 mg/dL Renal: Creatinine no greater than 2 mg/dL Other: Not pregnant or nursing Negative pregnancy test Fertile patients must use effective contraception during and for 6 months after study PRIOR CONCURRENT THERAPY: Biologic therapy: At least 2 weeks since prior immunotherapy and recovered No concurrent filgrastim (G-CSF) No concurrent immunotherapy Chemotherapy: See Disease Characteristics No prior nitrocamptothecin, irinotecan, or other camptothecin analog At least 2 weeks since other prior chemotherapy and recovered No other concurrent chemotherapy Endocrine therapy: No concurrent anticancer hormonal therapy Radiotherapy: See Disease Characteristics At least 2 weeks since prior radiotherapy and recovered No concurrent radiotherapy Surgery: At least 2 weeks since prior surgery and recovered No scheduled major surgery within 8 weeks following initiation of treatment