- Unlabelled: The purpose of this study was to evaluate the efficacy, toxicity, and safety of outpatient chemotherapy with weekly high-dose 5-fluorouracil (HD-5FU) in previously treated patients (pts) with metastatic colorectal cancer. Previously treated and failed pts with histologically confirmed, measurable metastatic colorectal cancer, performance status (WHO) 0-2 and adequate bone marrow function were eligible for treatment. Patients received 5FU (2.6 g/m2) as a 24-hour continuous infusion. Treatment was repeated weekly. A total of 202 cycles were given. Eighteen pts were enrolled. No pts achieved objective response. In 6 pts (33%), after 4 weeks of treatments, CEA level decreased 25% or more, and after 8 weekly treatments it rose again. Mild myelosuppression rarely occurred. Grade I nausea and vomiting occurred in 2 pts and Grade I diarrhea occurred in 2 pts. Mucositis was not observed. Conclusion: In our experience single agent, weekly, high dose 5-FU is well tolerated, but is ineffective as second-line treatment for metastatic colorectal cancer, and has only a marginal effect on CEA level.