Phase I and pharmacologic study of 72-hour infused 5-fluorouracil in man

The relationships between the administered dose, clearance, and the toxicity spectrum of 5-fluorouracil (5-FU) administered as 72-hour constant infusion have been studied in 21 patients with advanced cancer. This was done as a pilot study for possible future combination using 5-FU as a radiosensitizer. Individual patients tolerated up to 65 mg/kg/24 hours, but serious toxicity appeared once as low as 35 mg/kg. Limiting toxicity proved to be "mixed" with upper intestinal symptoms (nausea and vomiting), stomatitis, and central nervous system signs all occurring in various patients. Central nervous system effects (both cerebellar and vomiting) proved as troublesome as stomatitis. There was only a general link between the administered dose and the subsequent toxicity grade, but a reasonably quantitative relationship emerged when the serum 5-Fu levels obtained and the degree of patient toxicity were compared. The clearance of 5-FU was confirmed to be nonlinear over the entire dose range studied (25-65 mg/kg/24 hours), consistent with a two-compartment model of drug metabolism. One compartment appears to be systemic (extra-hepatic) metabolism (probably anabolic removal) which is saturated at just below 15 mg/kg/day. Doses above that level lead to drug accumulation. No steady state was reached, contrary to previous reports. At the higher infusion rates, clearance progressively approaches that predicted by the assumption that the second compartment is splanchnic blood flow and catabolism. While 5-FU can be administered as a 72-hour infusion as one possible schedule for use as a single agent or for combined modality studies, CNS effects are quite troublesome in comparison to longer infusions to toxicity.     

Phase I and pharmacologic study of oral ftorafur and X ray therapy in advanced gastrointestinal cancer

We have treated 15 patients with advanced gastrointestinal carcinoma with a cyclical regimen of combined Ftorafur (N1-((2-furanidyl-))-5-Fluorouracil, a 5-FU pro-drug) and external beam radiation. The Ftorafur (FT) was administered orally in daily doses of between 1.0 and 2.5 g/m2/day in 3 divided doses in a Phase I format. The drug was given daily for 5 days along with conventional X ray treatment portals and daily radiation doses of 250 rad on each of the first 4 days of each treatment cycle. The patients were then rested for a minimum of 10 days or until all significant side effects had passed. The total number of 1,000 rad cycles and radiation dose were dictated by tolerance and by normal organ dose limitations. The most common toxicity in general, and the most common limiting toxicity was nausea and vomiting, in contrast to oral FT alone where diarrhea is more prominent. Stomatitis was seen only once and no other form of serious toxicity was encountered. Two-thirds of the patients responded in subjective terms (pain relief). There was 1 partial response to FT alone (pulmonary metastases outside the treatment field). The sole patient whose treatment field was outside the abdomen (chest portals for esophageal carcinoma) developed pneumonitis which contributed to his death. No other delayed effects were noted. Serum FT levels were related to the ingested dose and in the microgram range while serum 5-FU levels were in the nanogram range indicating slow decomposition of FT into 5-FU. The therapy was reasonably well tolerated at doses of 2.0 g/m2/day or lower with abdominal radiation. FT offers the potential for replacing intra-venous infused 5-FU as a clinical radiosensitizer.     

Pharmacologic requirements for obtaining sensitization of human tumor cells in vitro to combined 5-Fluorouracil or ftorafur and X rays

The combined effects of X ray and 5-Fluorouracil (5-FU) in tissue culture have been studied using two human adenocarcinoma lines (HeLa and HT-29 cells). Both showed similar sensitivities to 5-FU, HeLa cells appearing somewhat more resistant to higher concentrations. Combined treatment of both cell types with 5-FU and X rays led to a time-dependent enhancement of cell killing ("radiosensitization"). Only post-radiation incubation had any effect, prior exposure to 5-FU being strictly additive. Enhanced cell killing by combined 5-FU and X rays could not be explained by either the infliction of additional acute damage in the immediate post-radiation period or an inhibitory effect of 5-FU on the repair of sub-lethal X ray injury. Rather, the enhanced cytotoxicity proved to be dependent on a damage expressed in time periods exceeding the duration of a cell doubling time in vitro. Overall, the data equally suggest that X rays may sensitize the cells to 5-FU. The enhanced cell killing is maximized if the cells are continuously exposed to 5-FU for 48 hours following the X ray exposure. These results indicate that clinical treatment regimens might be useful in evaluating 5-FU infusional scheduling in accordance with these unique requirements, which are not met by conventional bolus 5-FU and X ray therapy fractionation regimens. Ftorafur, a drug proposed to act as a slow release form of 5-FU, was found to show limited cytotoxic potential in vitro and did not significantly enhance cell killing after X ray exposure.     

Enhanced accumulation of 5-Fluorouracil in human tumors in athymic mice by co-administration of Ftorafur and Uracil

Human colonic tumors grown in athymic mice were tested for the effect of coincident uracil (U) and Ftorafur (FT) exposure versus FT alone on 5-Fluorouracil (5-FU) metabolism. Serum and tumor FT and 5-FU levels were studied as a function of time after FT +/? U injections. The combination of U + FT led to significantly higher tumor/serum 5-FU ratios than FT alone. The data indicate that the metabolism of 5-FU released from FT can be modulated by coincident U exposure in human tumor cells in vivo. Such combinations may be of use in the development of oral 5-FU pro-drugs for applications using 5-FU as an out-patient non-invasive radiosensitizer.     

A pharmacokinetic interaction study of docetaxel and cisplatin plus or minus 5-fluorouracil in the treatment of patients with recurrent or metastatic solid tumors

Background: The purpose of this study was to look at the pharmacokinetics of docetaxel, cisplatin-derived platinum and 5-fluorouracil (5-FU), when used in combination, to exclude potential clinically relevant pharmacokinetic interactions. Methods: Fifteen patients with recurrent or metastatic solid tumors were randomized to receive docetaxel 75 mg/m² and cisplatin 75 mg/m² in the first treatment course on day 1 and the same combination plus 5-FU 750 mg/m²/day on days 1–5 in the second course, or the two treatment courses in reversed order. Cycles were repeated every 3 weeks. A pharmacokinetic analysis was performed during the first two cycles. Results: Full pharmacokinetic data was available for 12 of the 15 patients. Treatment was tolerated well, with frequency of toxicity consistent with the safety profile known for docetaxel, cisplatin and 5-FU. Mean clearance values for docetaxel and cisplatin showed no statistically significant difference across the “triple” and the “double” combination treatments, and the mean pharmacokinetic parameters of all agents were within the ranges for previously reported single agent treatment. Conclusion: No clinically relevant pharmacokinetic interactions between docetaxel, cisplatin and 5-FU used in combination were noticed in this study.     

Phase II study of 5-fluorouracil and paclitaxel in patients with gemcitabine-refractory pancreatic cancer

Purpose  There is no effective salvage regimen for failed gemcitabine-based chemotherapy. This study evaluated the efficacy and toxicity of 5-fluorouracil and paclitaxel in patients with gemcitabine-refractory pancreatic cancer. Methods  Between January 2004 and December 2007, 28 patients with pancreatic cancer previously treated with gemcitabine-based chemotherapy were enrolled. 5-Fluorouracil 1,000 mg/m² was infused (days 1, 2, and 3) and paclitaxel 175 mg/m² (day 1) was administered every 4 weeks. The primary endpoint of this study was efficacy and toxicity and the secondary endpoint was time to progression and overall survival. Results  A total of 75 cycles were given, for a mean of 2.68 cycles per patient. The response could be evaluated in 20 patients. Two patients (10%) obtained a partial response, and four patients (20%) had stable disease. The median time to progression and overall survival was 2.5 and 7.6 months, respectively. Grade 3/4 hematological toxicity included neutropenia in six patients (21.4%), anemia in one (3.6%), and thrombocytopenia in one (3.6%). One (3.6%) patient experienced grade 4 neuropathy, and two (7.2%) patients experienced grade 3 diarrhea. Conclusion  The 5-fluorouracil and paclitaxel combination treatment seems to be effective in patients with advanced pancreatic cancer that did not respond to a gemcitabine-based regimen.     

Pharmacokinetics of levamisole in cancer patients treated with 5-fluorouracil

Purpose: To investigate the pharmacokinetics of levamisole and a metabolite, p-hydroxylevamisole in patients with colorectal cancer treated with 5-fluorouracil (5-FU). Methods: Following an intravenous bolus dose of 5-FU, 20 patients with colorectal cancer received oral doses of 50 mg levamisole every 8 h for 3 days. Immediately after the last dose, blood and urine samples were collected over at least an 8-h period. Samples were assayed for levamisole and p-hydroxylevamisole by GC/MS. The levamisole plasma and urine data were subjected to pharmacokinetic analysis using NONMEM software. Results: Substantial interpatient variability was observed in the levamisole plasma concentration-time curves. Patients with cardiovascular or gastrointestinal complications demonstrated altered absorption of levamisole. Pharmacokinetic parameter values for levamisole were similar to those obtained previously in healthy subjects and other cancer patients. Conclusions: There is no evidence that the pharmacokinetics of levamisole are altered by 5-FU administered immediately prior to levamisole administration. The relationship between the substantial intersubject variability in levamisole plasma concentration-time curves and clinical outcome following 5-FU/levamisole adjuvant chemotherapy should be examined. Received: 19 May 1999 / Accepted: 11 August 1999     

Biochemical modulation of 5-fluorouracil with brequinar: results of a phase I study

Biochemical modulation can increase the efficacy of 5-fluorouracil (5-FU). Pizzorno et al. have previously shown that brequinar, a de novo pyrimidine synthesis inhibitor, enhances the antitumor effect of 5-FU in vivo [Cancer Res 52: 1660–1665, 1992]. On the basis of their data, we conducted a phase I study of brequinar in combination with 5-FU in patients with refractory solid tumors. The initial dose (100 mg/m²) of brequinar was raised in 100-mg/m² increments in cohorts of three assessable patients. The initial dose of 5-FU was 500 mg/m², but escalation was allowed in patients who showed no significant toxic reaction. Brequinar was administered over 1 h and 5-FU over 2 h starting 18–20 h after the initiation of infusion of brequinar. Treatments were repeated weekly. Responses were evaluated after 4 weeks (one course) and then every 8 weeks thereafter. Pharmacokinetics of brequinar and determination of plasma uridine levels were performed in at least three patients at each dose level. Of the 25 patients registered in the study, 21 were assessable for toxicity studies. The dose of brequinar was escalated up to 600 mg/m². In addition, the dose of 5-FU was increased to 600 mg/m² as a result of a lack of a significant toxic reaction in the first nine patients. No objective responses were observed. One patient developed grade 3 stomatitis, and one developed grade 3 esophagitis at the 400 and 600 mg/m² dose of brequinar, respectively. Brequinar produced a dosedependent decrease in plasma uridine levels at doses up to 500 mg/m². No additional decrease in plasma uridine occurred with higher doses of brequinar, thus suggesting a plateau effect. This observation prompted us to terminate the study before reaching the maximum tolerated dose of brequinar. Our data indicate that brequinar in doses400 mg/m² results in significant biochemical modulation. The lack of toxicity seen at these doses of brequinar suggests that the initial dose of the effector agent 5-FU should be increased in future studies.Abbreviations 5-FU 5-Fluorouracil - PALA N-(phosphonacetyl)-l-aspartic acid - UXP total uridine nucleotide - AGC absolute granulocyte count - MTD maximum tolerated dose - ECOG Eastern Cooperative Oncology Group     

Phase I trial of the combination of 6-methylmercaptopurine riboside and 5-fluorouracil

6-Methylmercaptopurine riboside (MMPR) and 5-fluorouracil (5-FU) were administered sequentially to 12 patients in a phase I clinical trial. Toxicities included mild nausea and vomiting, as well as reversible leukopenia and thrombocytopenia. Maximal accumulation of 6-methylmercaptopurine ribonucleoside 5′-monophosphate (MMPR-P), the active metabolite of MMPR, in patients’ erythrocytes occurred between 2 and 6 h after the administration of MMPR and the degree of accumulation was dose-related. At 96 h after MMPR administration, MMPR-P was still detectable in patients’ erythrocytes. Although no clinical responses were documented, a modified dosage schedule of these drugs should be pursued based on the pharmacokinetic data obtained.     

Phase I study of hyperfractionated radiation therapy with protracted 5-fluorouracil infusion in patients with locally advanced pancreatic cancer

OBJECTIVE: This study investigated the maximum-tolerated dose of hyperfractionated radiation therapy with protracted 5-fluorouracil (5-FU) infusion in patients with locally advanced, unresectable pancreatic cancer. METHODS: Five cohorts of patients were scheduled to receive escalating doses of hyperfractionated radiation therapy (range, 45.6-64.8 Gy). All patients received two fractions of 1.2 Gy each (separated by 6 h) per day for 5 days a week, and received protracted 5-FU infusion (200 mg/m2/day) during the radiation course. The maximum-tolerated dose was defined as one dose level below the dose at which more than one third of 3-6 patients experienced dose-limiting toxicity. RESULTS: Twenty-nine patients were enrolled in this study. The most common toxicities were nausea/vomiting and anorexia. Although 1 patient developed bleeding from a gastric ulcer 3 months after the completion of chemoradiotherapy, the maximum-tolerated dose was not reached even at the highest dose level (level 5, 64.8 Gy). The median survival time was 12.2 months and the 1-year survival rate was 55.0%. CONCLUSION: The toxicity associated with our regimen was tolerable up to dose level 5 (64.8 Gy). We are currently conducting a phase II study of this hyperfractionated radiation therapy with protracted 5-FU infusion at a dose of 64.8 Gy.     

Phase II study of the combination of carboplatin and 5-fluorouracil in metastatic nasopharyngeal carcinoma

 A carboplatin and 5-fluorouracil (CF) chemotherapy protocol was designed to evaluate tumor response and toxicity in patients with metastatic nasopharyngeal carcinoma (NPC). Patients with metastatic NPC were treated with a maximum of eight courses of CF. Carboplatin was given at 300 mg/m² by intravenous bolus on day 1 and 5-fluorouracil at 1 g/m² per day by continuous infusion on days 1 – 3; cycles were repeated once every 3 weeks. A total of 42 patients were evaluable for response and toxicity. They received a median of 6 courses (range 2 – 8) of chemotherapy. The overall response rate was 38% (16/42), comprising 7 complete responses (CR, 17%) and 9 partial responses (PR, 21%). The median survival was 12.1 months (range 6 – 54.2 months). The treatment was well tolerated. Toxicity was mainly bone marrow suppression. There were four episodes of neutropenic fever, but no renal toxicity or treatment-related death was documented. The combination of carboplatin given at a fixed dose of 300 mg/m² for 1 day and 5-fluorouracil given at 1 g/m² per day for 3 days produced an objective response rate of 38% and tolerable side effects. Received: 21 October 1995 / Recepted: 1 March 1996     

Dihydropyrimidine dehydrogenase inactivation and 5-fluorouracil pharmacokinetics: allometric scaling of animal data,pharmacokinetics and toxicodynamics of 5-fluorouracil in humans

 The pharmacokinetics of 5-fluorouracil (5-FU) in different animal species treated with the dihy-dropyrimidine dehydrogenase (DPD) inactivator, 5-ethynyluracil (776C85) were related through allometric scaling. Estimates of 5-FU dose in combination with 776C85 were determined from pharmacokinetic and toxicodynamic analysis. Method: The pharmacokinetics of 5-FU in the DPD-deficient state were obtained from mice, rats and dogs treated with 776C85 followed by 5-FU. The pharmacokinetics of 5-FU in humans were then estimated using interspecies allometric scaling. Data related to the clinical toxicity for 5-FU were obtained from the literature. The predicted pharmacokinetics of 5-FU and the clinical toxicity data were then used to estimate the appropriate dose of 5-FU in combination with 776C85 in clinical trials. Results: The allometric equation relating total body clearance (CL) of 5-FU to the body weight (B) (CL=0.47B^0.74) indicates that clearance increased disproportionately with body weight. In contrast, the apparent volume of distribution (V_c) increased proportionately with body weight (V_c=0.58 B^0.99). Based on allometric analysis, the estimated clearance of 5-FU (10.9 l/h) in humans with DPD deficiency was comparable to the observed values in humans lacking DPD activity due to genetic predisposition (10.1 l/h), or treatment with 776C85 (7.0 l/h) or (E)-5-(2-bromovinyl)-2′-deoxyuridine (BVdUrd, 6.6 l/h). The maximum tolerated dose (MTD) of 5-FU in combination with 776C85 was predicted from literature data relating toxicity and plasma 5-FU area under the concentration-time curve (AUC). Based on allometric analysis, the estimated values for the MTD in humans treated with 776C85 and receiving 5-FU as a single i.v. bolus dose, and 5-day and 12-day continuous infusions were about 110, 50 and 30 mg/m² of 5-FU, respectively. Discussion: The pharmacokinetics of 5-FU in the DPD-deficient state in humans can be predicted from animal data. A much smaller dose of 5-FU is needed in patients treated with 776C85. Received: 6 October 1995/Accepted: 28 May 1996     

Phase I and pharmacokinetic study of 24-hour infusion 5-fluorouracil and leucovorin in patients with organ dysfunction.

BACKGROUND: Patients with hepatic or renal dysfunction are often treated with 5-fluorouracil (5-FU), but there are few data to confirm the safety of this practice. PATIENTS AND METHODS: Patients with solid tumors were eligible if they were able to fit into one of three organ dysfunction cohorts: I, creatinine >1.5 but < or =3.0 mg/dl and normal bilirubin; II, bilirubin >1.5 but <5.0 mg/dl with normal creatinine; or III, bilirubin > or =5.0 mg/dl with normal creatinine. 5-FU doses were escalated separately within each of the three cohorts. Leucovorin (LV) dosage was fixed at 500 mg/m(2). 5-FU was given as a 24-h infusion at 1000, 1800 or 2600 mg/m(2), and plasma concentrations were measured every 3 h during the first two infusions for each patient. RESULTS: Sixty-four patients were treated. Toxicities did not appear to be related to organ dysfunction cohort. A weekly dose of of 5-FU 2600 mg/m(2) produced dose-limiting toxicity (DLT) in six of 20 evaluable patients.These DLTs included grade 3 fatigue (n = 3), grade 2 neutropenia precluding weekly dosing (n = 1), grade 3 thrombocytopenia (n = 1) and grade 3 mental status changes (n = 1). There was no relationship between serum bilirubin or serum creatinine and 5-FU clearance. CONCLUSIONS: Patients with elevated bilirubin may be safely started on a weekly regimen of 5-FU 2600 mg/m(2) with leucovorin 500 mg/m(2) as a 24-h continuous infusion.     

Opiate effects on 5-fluorouracil disposition in mice

 Purpose: This study was performed to investigate the effects of morphine on the disposition of 5-fluorouracil (5-FU). Methods: Mice were injected subcutaneously (s.c.) with saline or morphine, 20 mg/kg. 5-FU was administered intravenously (i.v.) 30 min later as a single bolus or by constant infusion. Blood samples were obtained by orbital sinus puncture. Urine samples were obtained from the bladder after ligation of the external urethra. 5-FU concentrations in plasma and urine were determined by HPLC. Results: Morphine markedly elevated plasma levels of 5-FU given at doses of 100 to 860 mg/kg. The plasma clearance rate of a bolus dose of 100 mg/kg 5-FU was significantly reduced from 54 to 28 ml/min per kg and the elimination half-life was increased from 6.9 to 12.2 min by prior administration of morphine. When 5-FU was infused at 0.5 mg/kg per min, morphine reduced its plasma clearance rate from 145 to 94 ml/min per kg. Mice made tolerant by prior morphine administration required higher doses of this opiate to raise 5-FU levels as well as to cause analgesia. The effects of morphine on 5-FU disposition were antagonized by naltrexone. Excretion of 5-FU in urine was not affected by morphine treatment. Conclusions: The plasma clearance rate of 5-FU in mice is significantly reduced by concomitant use of morphine. This effect of morphine is due to reduced hepatic elimination of 5-FU rather than to a decrease in its renal excretion. Received: 22 December 1995 / Accepted: 25 May 1996     

A phase I study of recombinant human interferon alpha-2b combined with 5-fluorouracil and cisplatin in patients with advanced cancer

To determine the maximum tolerated dose (MTD) of escalating doses of interferon--2b (IFN, Intron A) with 5-fluorouracil (5-FU) and cisplatin (DDP) in patients with advanced cancer, 15 patients were accrued between May 1990 and July 1991. Primary sites were unknown (3), colorectal (3), head and neck (2), lung (2), gynecologic (1), gallbladder (1), sarcoma (1), anal canal (1) and pancreas (1). IFN was given s.c. on days 1–5 and then three times weekly with DDP (75 mg/m², day 1) and 5-FU [750 mg/m², days 1–5, continuous infusion (CI) on a 28-day cycle. The first two patients treated at level I (3×10⁶ U/m² s.c.) experienced possible neurotoxic deaths [massive cerebrovascular accident (CVA) and metabolic encephalopathy], and patient 3 had a grade 4 toxicity of performance status decline. Analysis of these events led us to exclude the enrollment of patients on i.v. morphine and of those with prior exposure to DDP. This resulted in grade 3 toxicity in terms of nausea, vomiting, fatigue and leukopenia but in no further CNS event. All patients were evaluable for toxicity but only ten were evaluable for response. Only two partial responses were seen, one in a patient with an unknown primary tumour and one in a patient with head and neck cancer. The combination of IFN is possible with 5-FU and DDP. The recommended dose of IFN is 2×10⁶ U/m² s.c. in patients with no prior exposure to DDP or i.v. morphine, given together with 5-FU (750 mg/m², days 1–5, CI) and DDP (75 mg/m², day 1) on a 28-day cycle.Supported in part by a grant from Schering Canada Inc.     

Phase I study of cetuximab in combination with 5-fluorouracil,mitomycin C and radiotherapy in patients with locally advanced anal cancer

Background5-fluorouracil (5FU) and mitomycin C (MMC)-based chemoradiotherapy (CRT) is standard treatment for anal squamous cell carcinoma. In this phase I study cetuximab was added and the primary aim was to determine the maximum tolerated dose (MTD) of 5FU and MMC in this combination.Methods and materialsPatients with locally advanced anal cancer, T2 (≥4 cm)–4N0–3M0, received weekly standard doses of cetuximab starting 1 week before CRT. Intensity modulated radiotherapy (IMRT) or volumetric modulated arc therapy (VMAT) with simultaneous integrated boost (SIB) was given to 57.5/54.0/48.6 Gy in 27 fractions to primary tumour/lymph node metastases/adjuvant lymph node regions. 5FU/MMC was given concomitantly on RT weeks 1 and 5 according to a predefined dose escalation schedule.ResultsThirteen patients were enrolled. Two patients discontinued cetuximab due to hypersensitivity reaction. The median age was 65 years (range 46–70), nine were females, and 85% had stage IIIB disease. Dose-limiting toxicity events (diarrheoa, febrile neutropenia and thrombocytopenia) occurred in 3 of 11 patients. The most common grade 3–4 side-effects were radiation dermatitis (63%), haematologic toxicity (54%), and diarrheoa (36%). No treatment-related deaths occurred. Three months following completion of treatment, ten patients (91%) had a local complete remission (CR), but two patients had developed liver metastases, yielding a total CR rate of 73%.ConclusionThe MTDs were determined as 5FU 800 mg/m² on RT days 1–4 and 29–32 and MMC 8 mg/m² on days 1 and 29 when combined with IMRT/VMAT with SIB and cetuximab in locally advanced anal cancer.     

Phase I dose-escalating study of 24-h continuous infusion of 5-fluorouracil in combination with weekly docetaxel and cisplatin in patients with advanced gastric cancer

Purpose

To determine the maximum-tolerated dose (MTD) of a 24-h continuous infusion of 5-fluorouracil (5-FU) when administered in combination with a fixed weekly dose of docetaxel and cisplatin in patients with advanced gastric cancer.

Methods

Patients with advanced gastric adenocarcinoma (n = 21) received a weekly regimen of docetaxel, cisplatin and 5-FU (DCF) for 3 consecutive weeks every 4 weeks. The doses of docetaxel and cisplatin were fixed at 33.3 and 30 mg/m², respectively. The dose of 5-FU was increased from a starting dose of 1,000 mg/m² to the MTD.

Results

A total of 53 cycles of chemotherapy were administered (median = 3 cycles/patient). The MTD of 5-FU was 1,750 mg/m². All 21 patients were assessed for toxicity and 19 patients (90%) were evaluated for response. Both grade 3–4 hematologic and non-hematologic toxicities occurred in less than 10% of patients and there were no treatment-related deaths. Among the 19 patients, we observed 1 complete and 4 partial responses for an overall response rate of 26% (95% CI: 6–46%). This rate increased to 39% (95% CI: 12–66%) in 13 chemotherapy-naïve patients.

Conclusions

A consecutive weekly DCF regimen at 4-week intervals appears feasible for advanced gastric cancer with a favorable toxicity profile. The recommended doses are 33.3 mg/m² of docetaxel, 30 mg/m² of cisplatin and 1,500 mg/m² of a 24-h continuous intravenous infusion of 5-FU. The response of this weekly regimen in our study was favorable and deserved further investigation in a phase II trial.     

Phase I trial of fluorouracil modulation by N-phosphonacetyl-L-aspartate and 6-methylmercaptopurine ribonucleoside

Inhibition of pyrimidine and purine synthesis has been demonstrated to potentiate 5-fluorouracil (5-FU) activity in preclinical models. Low-dose phosphonacetyl-l-aspartate (PALA) potentiates the incorporation of 5-FU into RNA, without detectably increasing its toxicity. 6-Methylmercaptopurine riboside (MMPR) results in inhibition of purine biosynthesis with elevation of phosphoribosyl pyrophosphate (PRPP), which in turn is believed to increase the phosphorylation and intracellular retention of 5-FU. We conducted a phase I clinical trial to determine the maximum tolerated dose of 5-FU in combination with low-dose PALA and a biochemically-optimized dose of MMPR. The regimen consisted of PALA 250 mg/m² given on day 1, followed 24 h later by MMPR 150 mg/m², and escalating doses of 5-FU from 1625 to 2600 mg/m² by 24 h continuous infusion. This regimen was repeated weekly. A group of 29 patients with a diagnosis of malignant solid tumor were entered; their median performance status was 1. The dose-limiting toxicity was mucositis, while other gastrointestinal toxicity was minimal. Two patients also experienced ischemic chest pain during the 5-FU infusion. The maximum tolerated dose of 5-FU in this combination was 2600 mg/m². Several responses were observed including a complete remission in a previously treated breast cancer patient and two partial responses in breast and colon cancer. MMPR pharmacokinetics were obtained from urine analyses in 21 patients on this trial; there was no correlation between the pharmacokinetics of MMPR and the toxicity observed. This regimen was well tolerated and phase II trials are warranted using PALA 250 mg/m², MMPR 150 mg/m², and 5-FU 2300 mg/m² by continuous infusion over 24 h.     

Investigations in vivo of the effects of carbogen breathing on 5-fluorouracil pharmacokinetics and physiology of solid rodent tumours

Purpose We have shown previously that carbogen (95% 0₂, 5% CO₂) breathing by rodents can increase uptake of anticancer drugs into tumours. The aim of this study was to extend these observations to other rodent models using the anticancer drug 5-fluorouracil (5FU). 5FU pharmacokinetics in tumour and plasma and physiological effects on the tumour by carbogen were investigated to determine the locus of carbogen action on augmenting tumour uptake of 5FU.Methods Two different tumour models were used, rat GH3 prolactinomas xenografted s.c. into nude mice and rat H9618a hepatomas grown s.c. in syngeneic Buffalo rats. Uptake and metabolism of 5FU in both tumour models with or without host carbogen breathing was studied non-invasively using fluorine-19 magnetic resonance spectroscopy (¹⁹F-MRS), while plasma samples from Buffalo rats were used to construct a NONMEM pharmacokinetic model. Physiological effects of carbogen on tumours were studied using ³¹P-MRS for energy status (NTP/Pi) and pH, and gradient-recalled echo magnetic resonance imaging (GRE-MRI) for blood flow and oxygenation.Results In both tumour models, carbogan-induced GRE-MRI signal intensity increases of 60% consistent with an increase in tumour blood oxygenation and/or flow. In GH3 xenografts, ¹⁹F-MRS showed that carbogen had no significant effect on 5FU uptake and metabolism by the tumours, and ³¹P-MRS showed there was no change in the NTP/Pi ratio. In H9618a hepatomas, ¹⁹F-MRS showed that carbogen had no effect on tumour 5FU uptake but significantly (p=0.0003) increased 5FU elimination from the tumour (i.e. decreased the t_1/2) and significantly (p=0.029) increased (53%) the rate of metabolism to cytotoxic fluoronucleotides (FNuct). The pharmacokinetic analysis showed that carbogen increased the rate of tumour uptake of 5FU from the plasma but also increased the rate of removal. ³¹P-MRS showed there were significant (p0.02) increases in the hepatoma NTP/Pi ratio of 49% and transmembrane pH gradient of 0.11 units.Conclusions We suggest that carbogen can transiently increase tumour blood flow, but this effect alone may not increase uptake of anticancer drugs without a secondary mechanism operating. In the case of the hepatoma, the increase in tumour energy status and pH gradient may be sufficient to augment 5FU metabolism to cytotoxic FNuct, while in the GH3 xenografts this was not the case. Thus carbogen breathing does not universally lead to increased uptake of anticancer drugs.     

Radical radiation therapy with 5-fluorouracil infusion and mitomycin C for oesophageal squamous carcinoma

Thirty-five patients with clinically staged non-metastatic squamous carcinoma of the oesophagus were treated with radiation combined with mitomycin C, and 5-fluorouracil (5-FUra) infusion. Twenty patients were planned for a split course regimen 2250-2500 cGy in 10 fractions and chemotherapy. This dose of radiation to be repeated with another course of chemotherapy after 4 weeks rest. Fifteen patients were planned for a single course 4500-5000 cGy in 20 fractions and a single course of chemotherapy. Thirty-one patients are available for a minimum follow-up of one year, 26 patients for a minimum follow-up of 2 years. All 35 patients are included in the survival and local relapse-free analysis. Survival at one year is 47% and at 2 years 28%. The local relapse-free rate at both one and 2 years is 48%. There was an improvement in survival and local relapse-free rate for the single course regimen compared to the split course; 2 years survival 48% versus 12% (p = 0.24) local relapse-free rate 79% versus 27% (p = 0.07). All patients receiving radiation and chemotherapy were compared with historical controls treated by radiation alone. This matching procedure was done independent of knowledge of outcome (two controls were matched/case). Patients were matched for age, sex. TNM stage, and total radiation dose. There was a significant difference in survival p = 0.004 and local relapse-free rate p = 0.05 for patients receiving radiation and chemotherapy.(ABSTRACT TRUNCATED AT 250 WORDS)