Phase I/II study of cyclophosphamide, doxorubicin, fluorouracil, and leucovorin for treatment of metastatic adenocarcinoma.

Leucovorin enhances the cytotoxicity of fluorouracil (5-FU) in patients with colorectal cancer and may increase the efficacy of combination chemotherapy regimens containing 5-FU. To determine the maximum tolerated dose of 5-FU with leucovorin for use in combination with cyclophosphamide and doxorubicin, we conducted a phase I/II trial in 20 patients. The doses of leucovorin (200 mg/m2 on days 1-5), cyclophosphamide (500 mg/m2 on day 1), and doxorubicin (40 mg/m2 on day 1) were held constant, while the dose of 5-FU was escalated in cohorts of patients beginning at 150 mg/m2 on days 1-5. Cycles were repeated every 3 weeks. Significant mucositis, diarrhea, and myelosuppression were infrequently observed in patients receiving up to 250 mg/m2 5-FU on days 1-5. In contrast, at a dose of 300 mg/m2 on days 1-5, three of six patients had granulocyte count nadirs of less than 500/microL during the first cycle of therapy, and two of these three had platelet counts of less than 25,000/microL. In addition, two patients treated at this dose had significant mucosal toxic effects, and three had insufficient recovery to permit a second course by day 22. Among 14 patients with assessable breast cancer, there were one complete and nine partial responses (response rate 71%). Leucovorin modulation of 5-FU can be safely incorporated into combination chemotherapy with cyclophosphamide and doxorubicin and provides a highly active regimen for treatment of metastatic breast cancer. Further study will be required to determine whether the addition of leucovorin significantly enhances the activity of this regimen.