Phase II clinical trial of parenteral hydroxyurea in combination with fluorouracil, interferon and filgrastim in the treatment of advanced pancreatic, gastric and neuroendocrine tumors

Purpose: Combined inhibition of ribonucleotide reductase (RR) and thymidylate synthase (TS), the enzymes responsible for a balanced supply of nucleotides for DNA synthesis, has been shown to induce synergistic antiproliferative effects in vitro. In the clinic, prolonged infusion of the RR inhibitor, hydroxyurea (HU), may be more effective than bolus or oral administration of drug. The purpose of the current study was to determine whether dose intensification of parenteral hydroxyurea in combination with fluorouracil could enhance the response rates of the combination against refractory upper gastrointestinal malignancies. Methods: A clinical trial of parenteral, weekly, high-dose HU in combination with weekly, high-dose infusional fluorouracil (5FU) was initiated in patients with advanced pancreatic and gastric cancer. Patients received 5FU 1.3 g/m² by continuous intravenous infusion (CIVI) daily over 48 h weekly in combination with HU 4.3 g/m² CIVI per day over 48 h weekly. Patients also received the biologic agent interferon alfa-2a 9 MU subcutaneously (s.c.) three times per week and filgrastim 480 μg s.c. on days 3 (starting after midday), 4, 5, and 6 each week. Each cycle required treatment on days 1 and 8 every 22 days. Results: Enrolled in the study were 32 patients, of whom 30 were evaluable. The median age was 56 years. Primary sites included pancreas (18), gastric (13) and islet cell (1). Despite filgrastim, the major toxicities were hematologic with 15 of 30 patients developing grade 3/4 granulocytopenia. Of the 30 patients, 4 developed grade 3/4 diarrhea. Interferon-mediated fatigue was mild. Of 12 evaluable patients with gastric cancer, 1 had a partial response, and there were no responders among patients with pancreatic cancer. Conclusions: Combined inhibition of RR and TS using this high-dose, weekly, 48-h infusional regimen is not an improvement over single-agent therapy in these tumor types.