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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/m(2) by continuous intravenous infusion (CIVI) daily over 48 h weekly in combination with HU 4.3 g/m(2) 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 microg 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.

Purpose: Combined depletion of pyrimidine and purine DNA precursors has resulted in therapeutic synergism in vitro. The aims of the current study were to test this strategy in patients with refractory tumors and to assess its effects on selected nucleotide pools., Patients and Methods: A single-institution phase II trial was initiated in patients with advanced carcinomas of the stomach and pancreas. Patients had measurable disease and had no prior chemotherapy except adjuvant fluorouracil (5FU) or gemcitabine. 5FU was administered by CADD + pump at 2.6 g/m(2) intravenously by 24-hour infusion on days 1, 8, 15, 22, 29, and 36. Parenteral hydroxyurea (HU) was administered at 4.3 g/m(2) as a 24-hour infusion concurrently with 5FU. Interferon alfa-2a (IFN-alpha2a) was administered at 9 million units subcutaneously on days 1, 3, and 5 each week. No drug was administered in weeks 7 and 8. Pharmacodynamic studies were performed to assess drug effects on levels of deoxyuridine triphosphate (dUTP) and thymidine triphosphate (TTP) pools in peripheral-blood mononuclear cells (PBMCs) before and 6 hours after treatment using a highly sensitive DNA polymerase assay., Results: There were 53 patients enrolled onto the study (gastric carcinoma, 31; pancreatic carcinoma, 22). The median age was 61 years, with 22% of patients > or = 70 years old. The predominant grade 3 to 4 toxicities were leukopenia (49%), granulocytopenia (55%), and thrombocytopenia (22%). Severe diarrhea occurred in 12%, mucositis in 0%, and vomiting in 10% of patients. Patients > or = 70 years had no greater incidence of toxicities. Among the 30 assessable patients with gastric carcinoma, there were two (7%) complete responders and 11 (37%) partial responders (median duration, 7 months). Among the 21 assessable patients with pancreatic carcinoma, there was one responder. Median survival among all patients with gastric carcinoma was 10 months and 13 months for patients with pancreatic carcinoma. Twenty-three patients had samples studied for levels of dUTP and TTP. There was no change in the levels of TTP before and after treatment. Furthermore, dUTP was detected in only five of 28 samples after treatment with no increase in the dUTP/TTP ratio., Conclusion: Combination therapy with high-dose, weekly infusional HU and 5FU with IFN-alpha2a modulation was well-tolerated with activity in gastric cancer. Patients > or = 70 years tolerated therapy as well as younger patients. This was the first study to correlate levels of TTP and dUTP after treatment with clinical outcome. In PBMCs used as a surrogate tissue, HU abrogated the 5FU-induced increase in dUTP levels without reversing the overall efficacy of the regimen.

Background: Preclinical and early clinical trials suggested that the biologic agent interferon beta ser (IFN beta ser) may augment the anticancer activity of 5-fluorouracil (5-FU). The current studies were undertaken to explore the optimal schedule of IFN beta ser and to determine whether the hematopoietic growth factor sargramostim (granulocyte-macrophage colony-stimulating factor) could reduce the hematologic and gastrointestinal toxicities of the chemotherapy., Methods: Three sequential, single-institution phase II trials using different regimens were initiated. Patients were required to have advanced, histologically documented colorectal carcinoma with no prior chemotherapy; to have adequate bone marrow, renal, and hepatic function; to be fully ambulatory; and to give informed consent. All patients received 5-FU, 750 mg/m2 intravenously as an infusion daily for 5 days, followed by 5-FU, 750 mg/m2, as an intravenous bolus every week beginning day 15. Patients in arm A received IFN beta ser, 9 MU subcutaneously, three times a week. Patients in arm B received IFN beta ser, 9 MU subcutaneously every day. Patients in arm C were treated exactly as in arm B but also received sargramostim, 250 micrograms subcutaneously on days they did not receive 5-FU. Beginning day 15, all patients received IFN beta ser exactly 10 minutes before receiving the 5-FU bolus., Results: There were 81 patients enrolled: 19 in arm A; 40 in arm B; and 22 in arm C. Myelosuppression and diarrhea were the most common toxicities. Increasing the frequency of IFN beta ser administration in arm B resulted in a doubling of the rate of diarrhea from 11% to 22%, and the addition of sargramostim in arm C failed to reduce this. Sargramostim did reduce the incidence of grade 3 to 4 leukopenia, but this did not allow intensification of dosing or result in improved response or survival among patients in arm C. IFN-mediated fatigue was also common, occurring in 37% to 43% of patients. Patients receiving IFN beta ser on the intermittent schedule tolerated full-dose therapy longer than those on the daily schedule (10 weeks versus 5 weeks, P < 0.01). The response rates in the three arms were 21%, 35%, and 27%; there was no difference in median survival (15 months for all three arms)., Conclusions: The combination of 5-FU and IFN beta ser was active in patients with advanced colorectal carcinoma, and survival with this regimen was comparable to or better than that with other modulating regimens. The intermittent schedule of IFN beta ser was better tolerated than than the daily schedule.

The aspartate transcarbamoylase inhibitor, N-(phosphonacetyl)-L-aspartate (PALA), synergistically enhanced the cytotoxicity of a combination of 5-fluorouracil (5-FU) and interferon-alpha (IFN) against human colon cancer cell lines in vitro. To test the efficacy of this combination in the clinical setting, patients with locally advanced or advanced gastric carcinoma were treated with the combination of PALA, 5-FU and IFN (PFI). Patients were required to have biopsy-proven disease beyond the scope of surgical resection, measurable disease, no prior chemotherapy, adequate bone marrow, renal and hepatic function, to be fully ambulatory and to have given informed consent. Drug was administered as follows: PALA, 250 mg/m2, 15 min i.v. infusion, days 1, 15, 22, 29, and then weekly; 5-FU, 750 mg/m2 daily x 5 as a continuous i.v. infusion beginning day 2, then at 750 mg/m2 days 16, 23 and 30, then weekly; IFN, 9 MU subcutaneously three times per week beginning day 2. There were 22 patients enrolled. The major toxicities were fatigue and associated neurotoxicity, with acceptable gastrointestinal and haematological toxicities. There was one complete responder (5%) and 3 partial responders (14%); two of these responses were durable (> 3 years). Despite this modest clinical activity, other regimens for advanced gastric cancer such as FAMTX and ELF appear to have greater activity with comparable toxicity.

Background: Combinations of 5-fluorouracil (5FU) and recombinant alfa-2a-interferon (IFN) are synergistic in vitro and have demonstrated activity in colorectal carcinoma, renal cell carcinoma, and urothelial tumors., Methods: A Phase II trial of the combination of 5FU, 750 mg/m2 daily x 5 followed by weekly bolus therapy, and IFN, 9 MU subcutaneously three times per week, was initiated in patients with esophageal carcinomas. Patients were required to have biopsy-proven squamous cell or adenocarcinoma of the esophagus, locally advanced or metastatic disease beyond the scope of surgical resection, and adequate performance status, renal, hepatic, and bone marrow function., Results: Twenty-one patients were enrolled; one patient was inevaluable for response because he had received prior chemotherapy, but was evaluated for toxicity. Eleven patients had metastatic disease, and 10 had locally advanced disease. Thirteen patients had squamous cell carcinoma and 8 adenocarcinoma. Toxicities were acceptable with no serious diarrhea and only two cases of serious stomatitis, although a greater than expected incidence of neurologic toxicity was observed. There were five responders (25%) including two patients with advanced or locally advanced disease rendered pathologically free of disease. One patient, initially considered surgically unresectable, was able to undergo a total thoracic esophagectomy after responding to treatment with 5FU/IFN, at which time only a single microscopic focus of carcinoma in situ was found. She remains alive and free of disease at 18+ months. A second patient who presented with metastatic disease and nearly complete obstruction of the esophagus regained normal swallowing function after treatment with 5FU/IFN; rebiopsy of all lesions revealed the patient to be pathologically free of disease. He survived over 2 years., Conclusions: This regimen employing a single cytotoxic agent has activity in esophageal carcinoma. Strategies employing biochemical modulation deserve additional investigation in the treatment of esophageal carcinoma.