- Unlabelled: This study is a retrospective analysis of response, toxicity and freedom from progression of two single-agent chemotherapy regimens in patients with previously treated metastatic colorectal cancer. Thirty-five patients with histologically confirmed measurable metastatic colorectal cancer received chemotherapy after failure of first-line 5-fluorouracil (5-FU) and leucovorin treatment. The median age was 61 years. Twenty-seven patients had liver metastases, 6 had local recurrence, 1 had retroperitoneal lymph node metastases and 1 had lung metastases. Eighteen patients received weekly 2600 mg/m2 5-FU and 17 patients received weekly 125 mg/m2 irinotecan (CPT-11). Treatment was given until disease progression. Total number of cycles was 202 for 5-FU and 248 for CPT-11. The relative dose intensity was 1.0 for 5-FU and 0.84 for CPT-11. No grade 3-4 toxicity was registered in patients who received 5-FU. Grade 3-4 toxicity rates were as follows in those who received CPT-11: vomiting 1 (5.9%) patient in 1 cycle, diarrhea 3 (17.7%) patients in 3 cycles and neutropenia in 3 (17.7%) patients in 3 cycles. No patients manifested febrile neutropenia. Two patients (11.8%) needed hospital admission because of toxicity: 1 for vomiting and 1 for diarrhea. No objective responses were observed in the 5-FU group of patients. Three patients (17.6%) who received CPT-11, achieved partial response with a median duration of 8 months. Stable disease was registered in 3 (17.6%) and 9 (52.9%) patients in 5-FU and CPT-11 groups respectively (p=0.05). Median time to progression was 3.3 months for patients who received 5-FU and 4.2 months for those treated with CPT-11 (not significant). One-year survival was 22.2% and 54.3% respectively (p=0.05). Conclusion: Weekly chemotherapy with CPT-11 is tolerated with acceptable toxicity and leads to a better response rate than weekly high dose 5-FU. It also significantly improves survival but does not prolong freedom from progression.