Background: Treatment of metastatic colorectal cancer (CRC) with raltitrexed results in an objective response rate (OR) and overall survival (OS) comparable to bolus 5-fluorouracil (5-FU). A phase III trial found raltitrexed to be inferior to continuous infusion of 5-FU (ci5-FU).
Patients and methods: This phase II trial studied the activity and toxicity of methotrexate-modulated ci5-FU (ci5-FU/MTX) after failure of raltitrexed in patients with metastatic CRC.
Results: Of 32 patients who received raltitrexed, 27 were evaluable for response. An OR was observed in 19%. Grade 3/4 toxicity occurred in 47% of patients. Eighteen patients received second-line ci5-FU/MTX. One complete response (CR) and five stable diseases (SD) were observed. CR and SD were observed in patients with raltitrexed-resistant disease. Toxicity to ci5-FU/MTX was mild and predictable, even in patients with severe toxicity under raltitrexed.
Conclusion: ci5-FU/MTX is ineffective after failure of raltitrexed in patients with metastatic CRC. However, response to ci5-FU/MTX in patients with raltitrexed-resistant disease indicates incomplete cross-resistance.