Modulation of fluorouracil by leucovorin in patients with advanced colorectal cancer: evidence in terms of response rate. Advanced Colorectal Cancer Meta-Analysis Project.

PURPOSE: A meta-analysis was performed on nine randomized clinical trials that compared fluorouracil (5-FU) with 5-FU plus intravenous (IV) leucovorin (LV) for the treatment of advanced colorectal cancer. DESIGN: The analysis was based on the most recently updated individual patient data from all trials. The end points of interest were tumor response and overall survival. RESULTS: Therapy with 5-FU plus LV administered either as weekly or monthly regimens showed a highly significant benefit over single-agent 5-FU in terms of tumor response rate (23% v 11%; response odds ratio (OR), 0.45; P less than 10(-7)). This increase in response did not result in a discernable improvement of overall survival (survival OR, 0.97; P = .57). The large number of patients who did not respond to treatment in both groups, and cross-overs from 5-FU alone to 5-FU plus LV are discussed as plausible explanations for the lack of a survival difference. CONCLUSION: These results confirm the advantage of 5-FU plus leucovorin over 5-FU alone in terms of objective tumor response. They also suggest that in planning future trials, tumor response should not be considered a valid surrogate end point for survival in patients with advanced colorectal cancer.