Abstract

PURPOSE: Eniluracil (776C85) is an effective inactivator of dihydropyrimidine dehydrogenase that allows continuous low-dose oral fluorouracil (5-FU) to be given with predicable oral bioavailability. We have assessed this as first-line oral chemotherapy for patients with advanced/metastatic breast cancer. PATIENTS AND METHODS: Patients with histologically proven, locally advanced or metastatic breast cancer without previous chemotherapy for advanced disease were entered onto this open-label phase II study. Patients received oral 5-FU 1.0 mg/m2 with eniluracil 10 mg/m2, both given twice daily for the first 28 days of each 35-day cycle, continuing until disease progression or unmanageable toxicity. RESULTS: Thirty-three patients were entered, with a median age of 53 years. Sixteen partial responses were seen in twenty-nine assessable patients (55%; 95% confidence interval, 37% to 73%), including responses in four (40%) out of 10 patients who had received prior adjuvant 5-FU. Seven patients had stable disease for at least 3 months with symptom improvement. Median response duration was 14 months (range, 10 to 18+ months). Toxicity was low. There were only two episodes of drug-related grade 3 nonhematologic toxicity (diarrhea and infection), and only 6%, 3%, and 3% of patients developed granulocytopenia, thrombocytopenia, and neutropenic sepsis, respectively. Mild (grade 1/2) diarrhea occurred in 39% of patients, hand-foot syndrome in 15%, nausea in 27%, and mucositis in 18%. Toxicity-associated delay and dose reduction occurred in only 2% and 5% of courses, respectively. CONCLUSION: First-line treatment with the combination of oral 5-FU and eniluracil has high activity in patients with advanced breast cancer comparable with the most active conventional cytotoxic agents but with strikingly less toxicity.