Effective initial therapy of advanced breast cancer with fluorouracil and high-dose, continuous infusion calcium leucovorin

The use of leucovorin (LV) to modulate fluorouracil (FU)-mediated inhibition of thymidylate synthase has been shown both in vitro and in vivo to improve the antitumor activity of this drug. Based on our previous demonstration that this combination was active in heavily pretreated patients with prior FU exposure, we performed a phase II study of FU and high-dose intravenous calcium LV in patients with advanced breast cancer who had been exposed to no more than one prior chemotherapy regimen.

Fifty-one female patients with metastatic breast cancer were entered onto this trial. Patients with metastatic disease limited to soft tissue, lymph nodes, skin, and pulmonary nodules were allowed no prior chemotherapy for advanced disease. Those with metastases in the liver or a lymphangitic pattern on chest x-ray were allowed either a single prior regimen for advanced disease or no therapy for metastatic disease if less than 1 year had elapsed since the completion of adjuvant chemotherapy. FU was given daily for 5 days at 400 mg/m2/d with calcium LV, 500 mg/m2/d, beginning 24 hours before and continuing 12 hours after the first and last FU doses, respectively.

The overall objective response rate among 45 eligible patients was 36% (95% confidence interval, 22% to 51%). Fourteen of 31 patients in the soft tissue category responded (45%), and two of 14 in the visceral category experienced an objective response (14%). The median response duration was 5 months. Toxicities were moderate leukopenia and mucositis.

FU plus LV is an active first-line regimen with antitumor efficacy comparable to that of the anthracyclines, which warrants further exploration in combination with other agents active in advanced breast cancer. FU plus LV in this schedule is also an excellent alternative for patients with medical contraindications to more intensive combination chemotherapy regimens.