Eniluracil plus 5-fluorouracil and leucovorin: Treatment for metastatic breast cancer patients in whom capecitabine treatment rapidly failed

Background As part of a comparative phase II study of eniluracil/5-FU/Lv vs. capecitabine (Xeloda), an oral 5-FU prodrug for MBC, patients with rapid PD during capecitabine therapy crossed over to take eniluracil/5-FU/Lv. Patients and Methods Ten evaluable patients with radiologically documented PD within 70 days of capecitabine treatment were treated with a modified oral weekly eniluracil/5-FU/Lv regimen. Results After switching to eniluracil/5-FU/Lv, 3 (30%) patients had PR. Six (60%) had SD, producing a total of 90% with PR or SD. The median PFS was 140 days (vs. 42.5 days for capecitabine). Four (40%) patients had > 7months PFS. Eniluracil/5-FU/Lv was well tolerated with mild to moderate diarrhea and nausea as the most common side effects. Conclusion These positive efficacy and safety results encourage a larger study in patients with rapid PD during capecitabine treatment. Eniluracil/5-FU/Lv might enable these patients to continue with oral 5-FU rather than switching to the generally less well tolerated intravenous microtubule-interfering agents. In addition, the eniluracil/5-FU/Lv regimen might also provide any overall survival contribution of 5-FU that, for pharmacokinetic reasons, was not provided by capecitabine and would not be provided if these patients progressed directly to the other approved treatments.