5-fluorouracil (5-FU) is widely used in the treatment of cancer. Over the past 20 years, increased understanding of the mechanism of action of 5-FU has led to the development of strategies that increase its anticancer activity. Despite these advances, drug resistance remains a significant limitation to the clinical use of 5-FU. Emerging technologies, such as DNA microarray profiling, have the potential to identify novel genes that are involved in mediating resistance to 5-FU. Such target genes might prove to be therapeutically valuable as new targets for chemotherapy, or as predictive biomarkers of response to 5-FU-based chemotherapy.

5-Fluorouracil: mechanisms of action and clinical strategies

BACKGROUND Intravenous bolus fluorouracil plus leucovorin is the standard adjuvant treatment for colon cancer. The oral fluoropyrimidine capecitabine is an established alternative to bolus fluorouracil plus leucovorin as first-line treatment for metastatic colorectal cancer. We evaluated capecitabine in the adjuvant setting. METHODS We randomly assigned a total of 1987 patients with resected stage III colon cancer to receive either oral capecitabine (1004 patients) or bolus fluorouracil plus leucovorin (Mayo Clinic regimen; 983 patients) over a period of 24 weeks. The primary efficacy end point was at least equivalence in disease-free survival; the primary safety end point was the incidence of grade 3 or 4 toxic effects due to fluoropyrimidines. RESULTS Disease-free survival in the capecitabine group was at least equivalent to that in the fluorouracil-plus-leucovorin group (in the intention-to-treat analysis, P<0.001 for the comparison of the upper limit of the hazard ratio with the noninferiority margin of 1.20). Capecitabine improved relapse-free survival (hazard ratio, 0.86; 95 percent confidence interval, 0.74 to 0.99; P=0.04) and was associated with significantly fewer adverse events than fluorouracil plus leucovorin (P<0.001). CONCLUSIONS Oral capecitabine is an effective alternative to intravenous fluorouracil plus leucovorin in the adjuvant treatment of colon cancer.

https://www.nejm.org/doi/pdf/10.1056/NEJMoa043116

Capecitabine as Adjuvant Treatment for Stage III Colon Cancer

PURPOSE: To compare the response rate, efficacy parameters, and toxicity profile of oral capecitabine with bolus intravenous (IV) fluorouracil plus leucovorin (5-FU/LV) as first-line treatment in patients with metastatic colorectal cancer. PATIENTS AND METHODS: We prospectively randomized 605 patients to treatment with oral capecitabine for 14 days every 3 weeks or 5-FU/LV by rapid IV injection daily for 5 days in 4-week cycles. RESULTS: The overall objective tumor response rate among all randomized patients was significantly higher in the capecitabine group (24.8%) than in the 5-FU/LV group (15.5%; P = .005). In the capecitabine and 5-FU/LV groups, median times to disease progression were 4.3 and 4.7 months (log-rank P = .72), median times to treatment failure were 4.1 and 3.1 months (P = .19), and median overall survival times were 12.5 and 13.3 months (P = .974), respectively. Capecitabine, compared with bolus 5-FU/LV treatment, produced a significantly lower incidence (P < .0002) of diarrhea, stomatit...

Comparison of Oral Capecitabine Versus Intravenous Fluorouracil Plus Leucovorin as First-Line Treatment in 605 Patients With Metastatic Colorectal Cancer: Results of a Randomized Phase III Study

PURPOSE: Docetaxel and capecitabine, a tumor-activated oral fluoropyrimidine, show high single-agent efficacy in metastatic breast cancer (MBC) and synergy in preclinical studies. This international phase III trial compared efficacy and tolerability of capecitabine/docetaxel therapy with single-agent docetaxel in anthracycline-pretreated patients with MBC. PATIENTS AND METHODS: Patients were randomized to 21-day cycles of oral capecitabine 1,250 mg/m2 twice daily on days 1 to 14 plus docetaxel 75 mg/m2 on day 1 (n = 255) or to docetaxel 100 mg/m2 on day 1 (n = 256). RESULTS: Capecitabine/docetaxel resulted in significantly superior efficacy in time to disease progression (TTP) (hazard ratio, 0.652; 95% confidence interval [CI], 0.545 to 0.780; P = .0001; median, 6.1 v 4.2 months), overall survival (hazard ratio, 0.775; 95% CI, 0.634 to 0.947; P = .0126; median, 14.5 v 11.5 months), and objective tumor response rate (42% v 30%, P = .006) compared with docetaxel. Gastrointestinal side effects and hand-foot ...

Superior Survival With Capecitabine Plus Docetaxel Combination Therapy in Anthracycline-Pretreated Patients With Advanced Breast Cancer: Phase III Trial Results

Purpose To compare the efficacy and safety of orally administered capecitabine (Xeloda; Roche Laboratories, Inc, Nutley, NJ), a novel fluoropyrimidine carbamate designed to mimic continuous fluorouracil (5-FU) infusion but with preferential activation at the tumor site, with that of intravenous (IV) 5-FU plus leucovorin (5-FU/LV) as first-line treatment for metastatic colorectal cancer. Patients and methods We prospectively randomized 602 patients to treatment with capecitabine 1,250 mg/m(2) administered twice daily days 1 to 14 every 3 weeks, or to the 4-weekly Mayo Clinic regimen (5-FU/LV) until disease progression or unacceptable toxicity. Results The primary objective, to demonstrate at least equivalent response rates in the two treatment groups, was met. The overall response rate was 18.9% for capecitabine and 15.0% for 5-FU/LV. In the capecitabine and 5-FU/LV groups, respectively, median time to disease progression was 5.2 and 4.7 months (log-rank P =.65); median time to treatment failure was 4.2 and 4.0 months (log-rank P =.89); and median overall survival was 13.2 and 12.1 months (log-rank P =.33). The toxicity profiles of both treatments were typical of fluoropyrimidines. However, capecitabine led to significantly lower incidences (P Conclusion Oral capecitabine achieved an at least equivalent efficacy compared with IV 5-FU/LV. Capecitabine demonstrated clinically meaningful safety advantages and the convenience of an oral agent.

Oral Capecitabine Compared With Intravenous Fluorouracil Plus Leucovorin in Patients With Metastatic Colorectal Cancer: Results of a Large Phase III Study

Purpose: Capecitabine (Xeloda) is a novel fluoropyrimidine carbamate rationally designed to generate 5-fluorouracil (5-FU) preferentially in tumors. The purpose of this study was to demonstrate the preferential activation of capecitabine, after oral administration, in tumor in colorectal cancer patients, by the comparison of 5-FU concentrations in tumor tissues, healthy tissues and plasma. Methods: Nineteen patients requiring surgical resection of primary tumor and/or liver metastases received 1,255 mg/m2 of capecitabine twice daily p.o. for 5–7 days prior to surgery. On the day of surgery, samples of tumor tissue, adjacent healthy tissue and blood samples were collected simultaneously from each patient, 2 to 12 h after the last dose of capecitabine had been administered. Concentrations of 5-FU in various tissues and plasma were determined by HPLC. The activities of the enzymes (CD, TP and DPD) involved in the formation and catabolism of 5-FU were measured in tissue homogenates, by catabolic assays. Results: The ratio of 5-FU concentrations in tumor to adjacent healthy tissue (T/H) was used as the primary marker for the preferential activation of capecitabine in tumor. In primary colorectal tumors, the concentration of 5-FU was on average 3.2 times higher than in adjacent healthy tissue (P=0.002). The mean liver metastasis/healthy tissue 5-FU concentration ratio was 1.4 (P=0.49, not statistically different). The mean tissue/plasma 5-FU concentration ratios exceeded 20 for colorectal tumor and ranged from 8 to 10 for other tissues. Conclusions: The results demonstrated the preferential activation of capecitabine to 5-FU in colorectal tumor, after oral administration to patients. This is explained to a great extent by the activity of TP in colorectal tumor tissue, (the enzyme responsible for the conversion of 5′-DFUR to 5-FU), which is approximately four times that in adjacent healthy tissue. In the liver, TP activity is approximately equal in metastatic and healthy tissue, which explains the lack of preferential activation of capecitabine in these tissues.

Kazushige Mori

Papers

Preferential activation of capecitabine in tumor following oral administration to colorectal cancer patients.