Phase II study of oral eniluracil, 5-fluorouracil, and leucovorin in patients with advanced colorectal carcinoma.
BACKGROUND
The oral administration of 5-fluorouracil (5-FU) is hindered by erratic bioavailability due to catabolism of 5-FU by the enzyme dihydropyrimidine dehydrogenase (DPD) in the gastrointestinal tract. Eniluracil is a potent inactivator of DPD which results in 100% oral bioavailability of 5-FU. Leucovorin (LV) is another biochemical modulator of 5-FU that potentiates inhibition of thymidylate synthase, the primary target of 5-FU. The goal of this study was to determine the antitumor activity and toxicity of an oral regimen containing eniluracil, 5-FU, and LV in patients with colorectal carcinoma.


METHODS
Sixty eligible patients who had previously untreated, measurable, metastatic colorectal carcinoma were treated with oral eniluracil 50 mg on Days 1-7, 5-FU 20 mg/m(2) on Days 2-6, and LV 50 mg on Days 2-6. Cycles were repeated at 28-day intervals.


RESULTS
The overall response rate was 13% (95% confidence interval [CI] = 6, 25%), with 1 complete response and 7 partial responses. Three additional patients had partial responses that were not confirmed at subsequent evaluations. The median time to progression of disease was 4.4 months (95% CI = 3.45, 7.69) and the median survival time was 12.6 months (95% CI = 9.1, 14.75). Grade 3-5 toxicity (1 toxic death) occurred in 51 patients (85%). Grade 4 neutropenia occurred in 25 patients (42%), and 18 patients (30%) had Grade 3-4 diarrhea. Twenty-one patients (35%) were hospitalized for toxicity, and 12 (20%) had febrile neutropenia. Baseline creatinine clearance was associated inversely with severe toxicity (P = 0.001).


CONCLUSIONS
Although antitumor activity was observed, the frequent occurrence of severe toxicity with this regimen limited its clinical utility. Alternate schedules with a more favorable therapeutic index are undergoing clinical testing and should be pursued. The high level of toxicity observed with orally administered low dose 5-FU underscored the potency of eniluracil as a biochemical modulator.
Divisions of Medical Science and Population Science, Fox Chase Cancer Center, Philadelphia, Pennslyvania, USA. nj_meropol@fccc.edu
N J
NJ
Meropol
D
D
Niedzwiecki
D
D
Hollis
R L
RL
Schilsky
R J
RJ
Mayer
D000284:Administration, Oral; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000964:Antimetabolites, Antineoplastic / Q000008:administration & dosage / Q000009:adverse effects; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000009:adverse effects / Q000627:therapeutic use*; D002277:Carcinoma / Q000188:drug therapy* / Q000401:mortality / Q000473:pathology; D015179:Colorectal Neoplasms / Q000188:drug therapy* / Q000401:mortality / Q000473:pathology; D050744:Dihydrouracil Dehydrogenase (NAD+); D018450:Disease Progression; D004791:Enzyme Inhibitors / Q000008:administration & dosage / Q000009:adverse effects; D005260:Female; D005472:Fluorouracil / Q000008:administration & dosage / Q000009:adverse effects; D006801:Humans; D002955:Leucovorin / Q000008:administration & dosage / Q000009:adverse effects; D008297:Male; D008875:Middle Aged; D010088:Oxidoreductases / Q000037:antagonists & inhibitors; D044925:Oxidoreductases Acting on CH-CH Group Donors; D013940:Thymidylate Synthase / Q000037:antagonists & inhibitors; D014498:Uracil / Q000008:administration & dosage / Q000009:adverse effects / Q000031:analogs & derivatives* / Q000494:pharmacology
D000964:Antimetabolites, Antineoplastic; D004791:Enzyme Inhibitors; C073482:eniluracil; D014498:Uracil; D010088:Oxidoreductases; D044925:Oxidoreductases Acting on CH-CH Group Donors; D050744:Dihydrouracil Dehydrogenase (NAD+); D013940:Thymidylate Synthase; D002955:Leucovorin; D005472:Fluorouracil