[Leucovorin and 5-FU for advanced gastrointestinal cancer]

During the last 40 years, 5-fluorouracil 5-FU) has been the drug of choice for treatment of patients with gastrointestinal cancer. However, its effectiveness is far from satisfactory. It has been determined that leucovorin (LV) potentiates the cytotoxic effect of 5-FU through prolonged inhibition of thymidylate synthase. A series of 10 trials comparing LV.5-FU with 5-FU alone were reported. A significantly higher objective response rate was seen with LV.5-FU, but there was no increase in survival. In randomized trials comparing low-dose and high-dose LV as modulates of 5-FU in treating advanced colorectal cancer, high doses of LV presented no advantage over low doses. Adjuvant LV.5-FU was compared to surgery alone in large group trials, demonstrated and a statistically significant decrease in disease and increase in overall survival. These data suggest that LV.5-FU is a very effective combination and most clinicians worldwide now regard it as the standard therapy for colorectal cancer.