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Folates have been used with cytotoxic agents for decades and today they are used in hundreds of thousands of patients annually. Folate metabolism is complex. In the treatment of cancer with 5-fluorouracil, the administration of folates mechanistically leads to the formation of [6R]-5,10-methylene-tetrahydrofolate, and the increased concentration of this molecule leads to stabilization of the ternary complex comprising thymidylate synthase, 2'-deoxy-uridine-5'-monophosphate, and [6R]-5,10-methylene-tetrahydrofolate. The latter is the only natural folate that can bind directly in the ternary complex, with other folates requiring metabolic activation. Modulation of thymidylate synthase activity became central in the study of folate/cytotoxic combinations and, despite wide use, research into the folate component was neglected, leaving important questions unanswered. This article revisits the mechanisms of action of folates and evaluates commercially available folate derivatives in the light of current research. Better genomic insight and availability of new analytical techniques and stable folate compounds may open new avenues of research and therapy, ultimately bringing increased clinical benefit to patients., (Copyright © 2016 The Authors. Published by Elsevier Ireland Ltd.. All rights reserved.)

The objective of the study was to investigate whether specific single nucleotide polymorphisms (SNPs) with influence on drug transport, biotransformation and repair mechanisms are associated with treatment outcome and toxicity in metastatic colorectal cancer (mCRC). We genotyped blood samples from 519 mCRC patients treated with first-line 5-fluorouracil and oxaliplatin +/- cetuximab for 17 SNPs in 10 genes involved in membrane transport (ABCC1 and ABCC2), drug biotransformation (GSTP1 and AGXT) and DNA repair (ERCC1, ERCC2, XRCC1, XRCC3, XPG and MSH6). The AGXT-rs34116584 and the ERCC2-rs238406 polymorphisms were significantly associated with progression-free survival (P=0.002 and P=0.001, respectively). Associations between 18 toxicity variables and SNPs were identified, although none were significant after Bonferroni correction for multiple comparisons. The study identified SNPs of potential use as markers of clinical outcome in oxaliplatin-treated mCRC patients. If validated in other studies, they could improve the selection of therapy in mCRC.

Purpose: 5-fluorouracil (5-FU) competes with uracil (Ura) as a substrate for dihydropyrimidine dehydrogenase (DPD). Low DPD activity impairs breakdown of Ura to dihydrouracil (UH₂) and is associated with toxicity during 5-FU-based chemotherapy. Calculation of the 5-FU dose is based on body surface area, and new tools are needed to individualize treatment. The aim of study was to measure Ura and UH₂ in saliva of patients with colorectal cancer and relate levels to treatment-induced toxicity., Methods: Saliva was collected from 73 patients with stage III colorectal cancer prior to adjuvant 5-FU-based treatment. Ura and UH₂ were analyzed by a column-switching HPLC method. Toxicity was evaluated before each treatment cycle and the highest grade was noted at end of treatment., Results: Toxicity was more common and severe among women compared with men. The Ura and UH₂ concentrations in saliva were 5.0 ± 6.8 and 5.0 ± 4.0 nmol/ml, respectively. The UH₂/Ura ratio was lower in women compared with men (1.2 ± 1.0 and 2.2 ± 2.5, respectively, p = 0.0026). Patients who needed to reduce the drug dose during treatment (or terminate treatment) due to toxicity had a lower ratio (1.3 ± 0.85) compared to patients who completed treatment without dose reduction (4.1 ± 4.3, p < 0.0001)., Conclusion: Sampling of saliva is a quick, noninvasive, safe and painless process that gives information about patients Ura and UH₂ levels prior to chemotherapeutical treatment. This information may be useful in order to predict and prevent occurrence of treatment-related toxicities which otherwise may limit drug administration.

Background: In Nordic countries, the standard treatment of colorectal cancer (CRC) in the adjuvant setting is bolus 5-fluorouracil (5-FU) plus leucovorin alone or in combination with oxaliplatin. 5-FU competes with the natural occurring pyrimidine uracil (Ura) as a substrate for dihydropyrimidine dehydrogenase (DPD; enzyme commission number 1.3.1.2). Low DPD activity is associated with toxicity during treatment. Pretherapeutic detection of DPD deficiency could prevent severe toxicity otherwise limiting drug administration. Assays showing that DPD deficiency impairs breakdown of Ura to dihydrouracil (UH(2)) seem promising for clinical use., Methods: Urine was collected from 56 untreated volunteers and 143 patients with CRC before adjuvant treatment. Ura and UH(2) were analyzed using a column-switching high-performance liquid chromatography method that incorporates reversed-phase and cation-exchange columns. Ura, UH(2), and UH(2)/Ura levels were related to toxicity., Results: Ura and UH(2) in patients were not different from controls. UH(2) was significantly higher in women compared with men. The UH(2)/Ura ratio, however, did not differ according to sex. Low UH(2) and UH(2)/Ura levels were associated with diarrhea in men. Women experiencing thrombocytopenia had significantly higher Ura compared with women with no thrombocytopenia. The UH(2)/Ura ratio correlated negatively with total toxicity score in men (r = -0.39, P = .020)., Conclusion: Pretherapeutic Ura and UH(2) levels per se may be related to risk of side effects during adjuvant 5-FU-based treatment, whereas the UH(2)/Ura ratio may not always reveal such a risk. Sex is a strong risk factor for toxicity, showing the importance of evaluating male and female patients separately., (Copyright © 2011 American Cancer Society.)

5-Fluorouracil (5-FU)-based regimens remain a cornerstone in the treatment of colorectal cancer (CRC). However, the attendant toxicity prevents these regimens from reaching maximum therapeutic potential. In this retrospective analysis, we examined the pretreatment expression of 18 genes in archival tumor bank samples from patients with advanced CRC to determine if one or more of the selected genes showed promise as either a prognostic or predictive marker of 5-FU-based treatment outcomes. One hundred and forty-four CRC patient samples (collected from 1983 to 2004) were analyzed via real-time PCR for gene expression. Univariate analyses were used to correlate gene expression with efficacy and time-to-event variables. Low thymidine phosphorylase (TP), dihydrofolate reductase, dihydropyrimidine dehydrogenase (DPD), excision repair cross-complementing 1 (ERCC1) and thymidylate synthase gene expression were associated with better time-to-progression in the entire population. Low TP, DPD and ERCC1 expression were independently associated with improved overall survival. Low TP gene expression was also predictive of response. This study suggests that TP gene expression in particular is a predictive as well as a prognostic biomarker for advanced CRC patients. Gene panels assessing pretreatment TP, DPD, ERCC1, dihydrofolate reductase and thymidylate synthase gene expression may help improve the therapeutic potential of 5-FU- or other novel antifolate-based regimens. Further analysis of the prognostic or predictive value of these genes in prospective trials in CRC patients seems warranted.

Background: Systemic palliative treatment with chemotherapy against advanced pancreas cancer has low effectiveness despite considerable toxicity., Aim: To investigate the safety, toxicity and tumour response of intraperitoneal 5-Fluorouracil (5-FU) with intravenous Leucovorin and to monitor 5-FU pharmacokinetics in plasma during intraperitoneal instillation with and without vasopressin in patients with non-resectable pancreas cancer., Patients/methods: Between 1994 and 2003, 68 patients with non-resectable pancreas cancer TNM stage III and IV, were enrolled to receive intraperitoneal5-FU instillation 750-1500 mg/m2 and intravenous Leucovorin 100 mg/m2 for two days every third week. Tumour response, performance status and toxicity were recorded. Seventeen patients were also treated with intravenous vasopressin 0.1 IU/minute for 180 minutes, during intraperitoneal 5-FU instillation. Area under the curve (AUC) and peak concentration (Cmax) of 5-FU in plasma were analysed., Results: The treatment was well tolerated with minor toxicity. One complete response (54.1+ months) and 2 partial responses were observed. Time to progression was 4.4 months (0.8-54.1+), and median survival was 8.0 months (0.8-54.1+). There was a significant reduction of 5-FU Cmax in plasma the second day of treatment if vasopressin was used (3.4+/-2.5 and 6.1+/-5.4 mumol/l, respectively, p<0.05). 5-FU AUC in plasma was not significantly affected by vasopressin either day of treatment., Conclusion: Intraperitoneal 5-FU is a safe treatment with low toxicity to patients with non-resectable pancreas cancer. Tumour response was 4.4% and median survival time 8.0 months. Addition of vasopressin did not significantly decrease plasma 5-FU AUC but reduced Cmax on day 2 of treatment.

Aim: A prospective randomized study was executed comparing two regimens of regional therapy for liver metastases from colorectal cancer., Methods: Eighteen patients were allocated to hepatic artery occlusion for 16 h followed by intraportal 5-fluorouracil (5-Fu) infusion (1000 mg/m(2)) for 5 days every sixth week (HAO). Twenty-one patients received intra-arterial 5-Fu infusion+Leucovorin (100 mg) i.v. for 2 days every second week (HAI). The follow up every third month included CT and CEA. Thirteen patients had limited extrahepatic cancer. At tumor progression regional therapy was stopped and systemic chemotherapy or the best supportive care was administered., Results: The study was discontinued after randomization of 39 patients. No significant difference in survival within patients with and without extrahepatic cancer was present. The mean survival was longer in the HAI group than for the HAO group (19 months versus 13 months, p=0.0147) (median 18 (8-37) versus 12 (2-26). PR and SD were registered in 8/18 in the HAO group and 17/21 patients in HAI group. The median time to progress was 4 (1-22) months versus 7 (1-23) months for the HAO and HAI group, respectively., Conclusion: Regional intraarterial infusion with 5-Fu gives significantly better survival than hepatic artery occlusion followed by portal infusion. A limited amount of extrahepatic cancer does not influence survival time. A trial comparing hepatic artery 5-FU infusion and Leucovorin versus the most effective systemic therapy is warranted.

Purpose: Despite more than four decades of fluoro-pyrimidine treatment in different cancers, the optimal schedule is still not known. The plasma half-life of 5-fluorouracil (5-FU) is extremely short and continuous infusion has gained popularity. In this study we explored whether repeated bolus 5-FU injections could improve the results., Patients and Methods: Forty-three patients with advanced gastrointestinal carcinoma, where no standard treatment was available, were included in the phase I study. The initial dose of 5-FU was 250 mg/m2 with 30 mg/m2 leucovorin, repeated three hours later. Treatments were repeated every week. Twenty-six patients were recruited in the following phase II after maximal-tolerated dose (MTD) was reached. Plasma was collected for 5-FU pharmacokinetics., Results: Diarrhoea was the dose-limiting toxicity (DLT), and was reached at 450 mg/m2. One complete and three partial responses (24%) were seen in the phase II study at 400 mg/m2. In addition, several patients had lasting subjective improvements. The treatments were well-tolerated but accumulated toxicity was seen after several months. Dose intensity was 89% after four months of treatment. A great interpatient variability was seen in 5-FU pharmacokinetics. The plasma AUC correlated with the 5-FU dose and toxicity, but not with the tumour response., Conclusion: A split of the 5-FU push bolus injection is possible with maintained treatment activity and surprisingly high doses can be tolerated; a weekly dose intensity of 800 mg/m2 could be reached compared with 500 mg/m2 in the standard Nordic FLv schedule.

The effect of different dose intensities of 5-fluorouracil (5-FU) in advanced colorectal cancer was investigated. A total of 312 patients were randomized to receive 400 mg/m2 (group A), 500 mg/m2 (group B) or 600 mg/m2 (group C) of 5-FU with leucovorin 60 mg/m2 on two consecutive days every second week. Treatment continued to progression. Pharmacokinetic analyses with calculation of the area under the concentration (AUC) were performed in 91 patients. The primary endpoint was survival, and secondary endpoints were time to disease progression, toxicity and, if the disease was measurable, tumour response. The study was well balanced in the three groups with respect to a number of patient characteristics. Crude survival as estimated by Kaplan-Meier plots was not statistically significantly different (p = 0.07) but tended to show the best results in the intermediate dose group (median survival 10, 12.5 and 10 months, respectively). Analyses of time to progression or death showed significant differences among the three groups (p = 0.02) with the longest progression-free interval in the intermediate group receiving 500 mg/m2. The objective response rates were 23%, 39% and 28%, respectively (p = 0.02). The actual/projected dose intensity (mg/m2/week) was 92%, 92% and 84%, respectively. AUC did not correlate with response or survival. The frequency of severe side effects in group C was significantly higher than that of groups A and B. The study indicated that an increase from 800 to 1000 mg/m2 of bolus 5-FU fortnightly improved the treatment results but a further increase only worsened the toxicity.

The present study was designed to investigate the effect of the antimetabolite 5-fluorouracil (5-FU) on the capacity of the oral epithelium and the dental pulp to induce a mitogen-driven T-cell proliferation. Inbred Lewis rats were given 6 i.v. injections of 5-FU (30 mg/kg or 50 mg/kg) over a period of 8 days. Suspensions of oral epithelial and dental pulpal cells were prepared. The costimulatory capacity of the accessory cells from treated animals was monitored by their ability to induce a mitogen (ConA)-mediated proliferation of T cells isolated from regional lymph nodes of untreated animals. Accessory epithelial cells from rats treated with the high dose of 5-FU, but not the low dose, induced a decreased T-cell proliferation compared to controls. Accessory pulpal cells from rats, treated with 30 mg/kg or 50 mg/kg of 5-FU, induced a lower T-cell proliferation. When MHC class II molecule depleted T-cell suspensions from lymph nodes of 5-FU-injected animals were incubated with ConA, a significant proliferative response was observed. This finding correlated with an increase of MHC class II molecule expressing cells detected after incubation, although no such cells were observed immediately following the initial purification step of T cells. This finding demonstrates that the accessory cells could partly restore their expression of MHC class II molecules during incubation. The results of the study suggest that the function of immunocompetent cells of the oral mucosa and dental pulp is influenced by treatment with 5-FU and that the function of accessory cells of the pulp is affected more than the function of accessory cells derived from the oral mucosa.

The present study was designed to study 5-FU pharmacokinetics after interferon. Weekly bolus 5-FU (500 mg/m2), immediately followed by leucovorin (60 mg/m2) was given in 14 weekly cycles to 55 gastrointestinal and breast cancer patients. Interferon-alpha was given on days 2, 4 and 6, starting from cycle 2 at a dose of 0.5 million units (MU) and stepwise increased to 12 MU in cycles 12 and 13. Five patients could not tolerate the treatment even at the lowest dose of interferon and 22 patients were unavailable for the pharmacokinetic analysis because of dose reductions of 5-FU. Five patients were able to follow the protocol to 12 MU, whereas most patients were unable to continue owing to toxicity. 5-FU pharmacokinetics was analysed every second cycle. Peak concentration and AUC were increased after 12 MU of interferon, but no other significant influence of interferon on pharmacokinetic parameters of 5-FU was observed.

The use of bolus 5-fluorouracil (5-FU) as a short-term infusion over 10-30 min is increasing at the cost of a push injection, mainly due to practical advantages. Since even a short prolongation of the administration time results in lower 5-FU peak and area under the curve (AUC) levels, there might be a risk of decreased efficacy. The aim of this study was to compare a rapid intravenous (i.v.) 5-FU injection and a short-term 5-FU infusion with respect to objective responses and toxicity in patients with advanced colorectal cancer. 203 patients with measurable advanced colorectal cancer were randomised to bolus 5-FU either as an injection for 2-4 min or as a short-term infusion lasting 10-20 min. In both groups, the 5-FU dose was 500 mg/m2 and leucovorin 60 mg/m2 was given 40 min after the start of 5-FU. Treatment was given on two successive days every other week until progression. Objective tumour regression was seen in 27/100 (27%) in the injection group and in 13/103 (13%) in the infusion group (P = 0.02). Severe toxicity was rare and did not differ significantly between the groups. Progression-free survival tended to be longer in the injection group (P = 0.07), but overall survival did not differ between the groups. Bolus 5-FU should be administered as a rapid i.v. injection rather than as a short-term infusion, since the former rate of administration results in a higher response rate without being significantly more toxic.

Eradication of micrometastases is the goal for adjuvant therapy following a radical surgical procedure for cancer. We report an experimental study with 5,10-methylenetetrahydrofolate (5,10-CH2FH4) modulation of 5-fluorouracil (5-FU) cytotoxicity in adjuvant treatment. A colon adenocarcinoma cell suspension was inoculated intrahepatically in a rodent experimental model. Intravenous 5-FU (30 mg/kg) in combination with 5,10-CH2FH4 (15 mg/kg or 30 mg/kg) was administered after 1, 2, 3, 4 and 7 days. 5-FU alone reduced the tumor take to fifty percent compared to one hundred percent tumor take in control animals (p < 0.05), while 5-FU in combination with 5,10-CH2FH4 (regardless of folate-dose) eliminated tumor take (p < 0.0001). This makes 5,10-CH2FH4 a promising agent for modulation of 5-FU cytotoxicity in adjuvant cancer treatment.

We undertook a multicenter phase II trial of 5-fluorouracil (5FU) + 1-leucovorin (1-LV) in previously untreated patients with metastatic colorectal cancer to determine the response rate, response duration, time to progression, survival, and toxicity. Patients were treated with i.v. 5FU 370 mg/m2/day and 1-LV 100 mg/m2/day x 5 every 28 days. Toxicity and response were determined by WHO criteria. One hundred and twenty-six patients were entered, and 119 patients were eligible and evaluable. Eighty-eight patients had colon cancer and 37 had rectal cancer. The male:female ratio was 58:68. The mean age was 62.2 years. ECOG performance status distribution was 0 (39.7%), 1 (46%), and 2 (11.9%). The median number of courses of therapy administered was 4.5. Severe- or life-threatening stomatitis or diarrhea, nausea, and granulocytopenia occurred in 17.6, 23.2, 17.6, and 15.9% of patients, respectively. The response rate was 22/119 [18.5%; 95% confidence interval (CI) of 12.0-26.6]. Median response duration was 188 days (95% CI of 111-248 days). Median survival was 379 days (95% confidence interval of 289-452 days). These results indicate that when 1-LV is combined with 5FU, toxicity is similar in pattern and severity to that of the d,1 racemic mixture. The overall efficacy of 1-LV + 5FU is comparable to a recent metaanalysis.

The pharmacokinetics after 20 min intravenous infusion or a 2 min bolus (push) injection of 5-fluorouracil (500 mg/m2) were studied in 14 colorectal cancer patients. Treatment effects and toxicity related to the administration technique of 5-fluorouracil were retrospectively analysed in 198 colorectal cancer patients. The AUC after bolus injection was 6158 +/- 874 micromol/l*min compared to 3355 +/- 428 micromol/l*min after short-time infusion of 5-fluorouracil (p < 0.01). The mean peak-level after bolus injection was 341 +/- 34 microM versus 161 +/- 17 microM after a short-time infusion (p < 0.01). Patients receiving bolus injections had significantly better treatment result (32% partial remission) than patients receiving infusion (10% partial remissions, p < 0.001). Toxic side-effects were more frequently encountered after bolus injection but subjective improvement was also more frequently experienced by these patients. Bolus 5-fluorouracil push injection rather than a short-time infusion appears to be the more efficient administration technique.

The effects of the two diastereoisomers of 5-formyltetrahydrofolate on tumour growth, thymidylate synthase (TS, EC 2.1.1.45) levels, and potentiation of 5-fluorouracil cytotoxicity were studied in an in vivo rat colon carcinoma model, transplanted to liver. The animals were randomized into eight groups, treated with daily i.v. tail vein injections of racemic (d,l)-5-formyltetrahydrofolate (5-CHO-FH4), 15 mg/kg, (1)-5-CHO-FH4 7.5 mg/kg, and (d)-5-CHO-FH4 7.5 mg/kg, 5-fluorouracil (FUra) 30 mg/kg, (d,l)-5-CHO-FH4 15 mg/kg+FUra 30 mg/kg, (l) 5-CHO-FH4 7.5 mg/kg+FUra 30 mg/kg, and (d)-5-CHO-FH4 7.5 mg/kg+FUra 30 mg/kg, and a sham-treated control group. The average tumour size of the groups was equal at the start of treatment. After six days' treatment the average tumour sizes were at laparotomy 3.3 +/- 1.0 g in the (d/l)-5-CHO-FH4 treated group, compared to 2.0 +/- 0.1 g in the FUra treated group and 7.1 +/- 3.1 g in the controls. Natural (l)-5-CHO-FH4 promoted tumour growth (average tumour weight 10.8 +/- 4.0 g), whereas the unnatural (d)-5-CHO-FH4 alone retarded it (average tumour weight 1.2 +/- 0.40 g). (l)-5-CHO-FH4 induced a significant increase in tumour tissue TS levels by [3H]FdUMP radioligand assay (27.5 +/- 8.4 pmol/g tumour tissue) compared to controls (16.8 +/- 6.1 pmol/g tumour tissue). Increases in 5,10-methylenetetrahydrofolate and tetrahydrofolate occurred with FUra alone, with a further statistically significant increase in both folates with the addition of (d)-5-CHO-FH4 to FUra.

Transplantable nitrosoguanidine-induced rat colonic carcinoma was transplanted into the liver of 49 rats in six different series during three years. Tumor growth in vivo was surveyed by repeated laparotomy at day eight and day seventeen, and 25 rats were treated with 5-fluorouracil (30 mg/kg body weight) once a day, between day 8 and day 17. Tumor take was one hundred per cent and the tumor growth rate was similar throughout the experimental period. No animals died due to treatment or due to progressive tumor growth. The animals treated with 5-fluorouracil revealed a 5 per cent weight loss compared to the controls but no other signs of health deterioration were observed. The tumors treated with 5-fluorouracil had a 70 per cent decrease of growth rate compared to control rats. Exposure of the tumor cells in vitro to 5-fluorouracil induced a dose--related decrease in surviving cells with a 50 per cent reduction of surviving cells 48 hours after exposure to 0.01 mg/ml of 5-fluorouracil. Thus, we present here a new, feasible and reproducible animal model, excellently suited to in vivo and in vitro studies of fluorinated pyrimidines and solid tumor growth.

In a rat liver tumour system with a nitrosoguanidine-induced carcinoma and in an in vitro system with the same tumour, the effect of allopurinol on the toxicity and antitumour effect of 5-fluorouracil (5-FU) was explored. Two doses of 5-FU, 30 and 60 mg/kg b.w. intraperitoneally (i.p.), were tested with a large dose of allopurinol subcutaneously (s.c.( (300 mg) in rats. The drugs were given for three consecutive days. The lethal toxicity of 60 mg 5-FU i.p. could not be counteracted by allopurinol. Allopurinol and 30 mg 5-FU reduced the tumour growth rate more than 5-FU alone. The spleen was smaller, as a sign of increased toxicity, without allopurinol. The concentration of allopurinol and its metabolites in the general circulation was high. In vitro, there was no additive or specific effect of allopurinol. These results indicate some in vivo metabolic modulation of 5-FU efficacy by allopurinol if 5-FU is administered intraperitoneally and allopurinol systemically.

Recent experimental and clinical work has shown that leucovorin potentiates the cytotoxic effect of 5-fluorouracil (5-FU). To investigate the adjuvant role for this combination, 5-FU, 30 mg/kg, combined with leucovorin, 15 mg/kg, was administered intraperitoneally on 3 consecutive days beginning on the same day as tumor cell inoculation in the liver. Tumor take and tumor volume were registered on day 14, followed by recording of survival time. The results of the combined treatment were compared with treatment with 5-FU alone. Leucovorin in combination with 5-FU, but not 5-FU alone, significantly reduced the tumor take compared with untreated animals (p less than 0.01). The combination also resulted in smaller tumors compared with untreated animals (p less than 0.001) or with animals given 5-FU alone (p less than 0.01). The present study supports the use of leucovorin in combination with 5-FU as adjuvant treatment of patients with primary colorectal cancer.

Parameters for inhibition of thymidylate synthetase were studied after sequential methotrexate/5-fluorouracil (5-FU) administration in a dimethylhydrazine (DMH)-induced transplantable rat colon carcinoma. Tumor-bearing rats were treated with methotrexate (MTX) 40 mg/kg IP Bolus 5-FU, 100 mg/kg IP, was injected after 24 h. Micromethods for assay of 5-fluoro-2'-deoxyuridylate (FdUMP) and thymidylate synthetase (TS) were used to study the in vivo intracellular pharmacokinetics of 5-FU. Formation of FdUMP was equally rapid in tumors regardless of MTX pretreatment, with peak values found at 30 min. Although MTX pretreatment did not increase peak FdUMP levels, it appeared to result in increased persistence of FdUMP, well in excess of available TS-binding sites, at 24 and 48 h. The combination therapy was less effective in terms of TS inhibition over the first 8 h after 5-FU administration, but may have been associated with improved TS inhibition at later time points. Total levels of TS (TStot) steadily increased from a pre-5-FU treatment level of 18.8 pmol to more than 40 pmol/g at 24 h. MTX per se had no apparent effect on baseline TStot levels or on the 5-FU-mediated increases in TStot. We conclude that MTX and 5-FU were antagonistic in terms of TS inhibition over the first 8 h after 5-FU in this DMH-induced rat colon carcinoma, but were possibly synergistic in increasing persistent levels of FdUMP and TS inhibition at later time points. The observation that 5-FU treatment can result in progressive increases in TS levels in some tumors suggests that this may be an important mechanism of 5-FU resistance.

To evaluate the resorption of intravesically instilled 5-fluorouracil a single dose of 250 or 1,000 mg. was injected into the empty bladder for 3 hours in 17 patients. The concentration of 5-fluorouracil in serum during instillation was recorded. A microbiologic agar plate method was used for the assay. No measurable 5-fluorouracil concentrations were recorded in the systemic blood of patients with undamaged bladder mucosa and low levels (less than 100 ng./ml. serum) of 5-fluorouracil were found in the systemic circulation of patients with mucosal lesions.

Fifty-four patients with metastatic adenocarcinoma received i.v. bolus 5-fluorouracil, 500 mg/m2, prior to surgical biopsy of tumor at 20-400 min, for analysis of biochemical parameters of resistance to thymidylate synthase (TS) inhibition. The majority of patients, 37, had colon or rectal adenocarcinoma, five had breast cancer, five had gastric primary disease, four had pancreatic adenocarcinoma, and three had hepatocellular adenocarcinoma. Fluorodeoxyuridylate (FdUMP) was assayed by isotope dilution of [3H]FdUMP binding to bacterial TS; free and total TS was determined by [3H]FdUMP binding; and deoxyuridylate (dUMP) was assayed by conversion to [14C]thymidylate. Free levels of TS were lower in breast cancers, 0.08 +/- 0.06 pmol/g, than in other histologies (overall average, 1.41 +/- 2.25), associated with significantly greater percentages of TS inhibition (88.6% versus 62.0% overall). Colorectal tumors showed significantly greater FdUMP levels than other gastrointestinal malignancies, associated with somewhat lower free TS values. Plots of FdUMP levels, or (FdUMP/dUMP) x 100 values versus percentages of TS inhibition suggested minima of 75 pmol/g and 0.10, respectively, for achieving maximal enzyme inhibition. Analyses of normal tissues showed: poor TS inhibition in liver and normal colonic mucosa, related to low FdUMP levels; and very high dUMP levels in bone marrow leukocytes suggestive of reactive increases in dUMP as an important mechanism of recovery in this tissue. Among the 30 of the 37 colorectal tumors that showed suboptimal (less than 85%) inhibition of TS, 16 (53%) showed FdUMP levels less than 75 pmol/g, 8 (27%) showed relatively high dUMP levels (over 35 nmol/g), and 16 (53%) showed poor efficiency of inhibition of TS, with the major overlap between these mechanisms of resistance being high dUMP and poor binding in 6 (20%). These data provide a strong rationale for administration of leucovorin to the majority of patients receiving 5-fluorouracil, since increased intratumoral reduced folates potentially can overcome multiple mechanisms of resistance including low FdUMP, high dUMP, and high total TS levels, in addition to that caused by isolated folate deficiency.

Blood levels of 5-fluorouracil are quantitatively determined by isotachophoresis. Serum is deproteinized, purified on an ion-exchange column and concentrated to 20 microliter, and the drug is measured isotachophoretically. Down to 50 pmol (6.5 ng) of the drug can be determined in serum with a methodological error of +/- 6%. The method can be used for routine control of patients undergoing therapy with the drug.

The formation of FdUMP and the inhibition of TS were studied in a subcutaneously growing transplantable rat colon carcinoma and in regenerating rat liver following bolus administration of 5-FU, with or without HPP pretreatment. In tumor, peak levels of FdUMP at 30 min following bolus 5-FU, 100 mg/kg, averaged 4931 +/- 587 pmol/g. Pretreatment with HPP, 50 mg/kg, 24 h and 1 h before 5-FU, reduced the peak FdUMP level to 2085 +/- 387 pmol/g. The inhibition of TS by 5-FU treatment was greater than 95% by 30 min, and after 48 h residual enzyme inhibition averaged 40%. No effect on TS inhibition by 5-FU treatment could be observed as a result of HPP pretreatment. The levels of TStot increased linearly after 5-FU treatment and doubled within 48 h. In regenerating rat liver, neither FdUMP levels nor TS inhibition, studied at 1 h after bolus 5-FU, were affected by HPP pretreatment.

5-Fluorouracil (5-FU) was administered to 8 patients with malignant liver tumours either by regional portal or general intravenous infusion. During continuous portal infusion of 15 mg 5-FU/kg/24 h, systemic serum-concentrations were generally below 100 ng/ml and no side-effects were seen. Intravenous infusion of the same dose was accompanied by serum-concentrations above 100 ng/ml and bone-marrow depression. This preliminary study indicates that there are better prerequisites for high anti-toumour effect and low frequency of side-effects during portal infusion of 5-FU than during general intravenous administration to patients with liver tumours.

The pharmacokinetic conditions for oral administration of 5-fluorouracil (5-FU) were investigated in 16 patients with malignant liver tumours. The concentration of 5-FU in portal and systemic blood was determined by a microbiologic method every 10 min. during 2 hours after oral or intravenous administration of a standard dose of 250 mg 5-FU ( approximately 4 mg/kg b. wt.) or 15 mg 5-FU/kg b. wt. The drug was rapidly absorbed after oral administration with peak values within 10-30 min. 25% of the lower and 40% of the higher oral dose reached the systemic circulation. The reduction of systemic bio-availability was partly accomplished by a loss in the gastrointestinal tract and partly by extraction by the liver. The hepatic extraction ratio was calculated to 0.56 and 0.26 after the lower and the higher dose respectively indicating a saturable process. The availability of 5-FU was significantly higher in portal blood than in systemic blood after oral administration. The opposite conditions were found after intravenous administration. Thus, oral administration of 5-FU to patients with malignant liver tumours seems rational.

Reported 5-FU-induced cardiac side effects may be explained by drug-induced hemodynamic changes and/or by direct myocardial toxicity due to regional drug uptake. This question was studied in 11 animals given constant infusions and 6 animals given bolus 5-FU infusions into the hepatic artery. Six animals, which received normal saline infusion, served as controls. A second aim was to study possible pulmonary drug clearance. Aortic, pulmonary arterial, and coronary sinus plasma 5-FU concentrations were determined during constant and after the bolus infusions of 5-FU. The V5 ECG, aortic, pulmonary arterial, and right atrial pressures were recorded continuously, and cardiac output and coronary sinus blood flow were recorded intermittently in all animals. No significant alterations in hemodynamic variables were seen during constant infusion. After the bolus infusion, an increased arterio-mixed venous oxygen content difference was recorded. Pharmacokinetic data after 3-min infusions indicated pulmonary drug uptake and release; during constant infusions, the data indicated myocardial drug uptake. As there were no alterations in myocardial oxygen demand or supply or in systemic hemodynamics during this myocardial drug uptake, it is likely that the cardiotoxicity is related to the direct effects of the drug on cardiac myocytes.

The pharmacokinetics of 5-fluouracil were studied in 9 patients with a history of bladder malignancies. A single dose of 250 mg. 5-fluorouracil was given orally and the renal clearance of active 5-fluorouracil was approximately 40 ml. per minute. The maximum serum (1,100 ng./ml. serum) and urinary concentrations (49,000 ng./ml. urine) of 5-fluorouracil occurred 20 and 40 minutes after administration, respectively. The urinary concentration per se is highly cytotoxic, whereas the short-lasting serum concentration previously has been proved to be without general cytotoxic effects even after continuous use of the drug for years. Although high concentrations of 5-fluorouracil are noted in the urine the antitumor effects of this treatment must be investigated further.

Rats with an experimental solitary liver tumor of a nitrosoguanidine-induced colonic adenocarcinoma were subjected to hepatic artery ligation (HAL) alone or in combination with 5-fluorouracil (5-FU) in three different doses, with or without the addition of allopurinol. The drugs were injected i.p. on 3 consecutive days before or after the HAL procedure. HAL alone significantly reduced the tumor growth compared with the control procedure (P less than 0.001). This observation was correlated with a significantly prolonged survival for the ligated animals (P less than 0.01). The administration of a low dose of 5-FU (15 mg/kg per day) in combination with allopurinol (100 mg/kg per day) enhanced tumor growth compared with that in animals treated with 5-FU only (P less than 0.01) or nontreated animals (P less than 0.05). A significant increase in survival was observed in animals given a high dose of 5-FU (60 mg/kg per day) after HAL compared with non-treated animals (P less than 0.001) as well as animals subjected to HAL alone (P less than 0.02). All animals receiving more than 15 mg/kg per day 5-FU before HAL succumbed within 10 days. The addition of allopurinol did not protect the animals against this mortality. These observations indicate that the effect of HAL followed by 5-FU is dose-dependent and that, at least in this treatment modality, allopurinol does not modulate the toxicity of 5-FU.

Single surgical biopsies of solid tumor were obtained at 20 to 240 min after drug administration in 21 patients given first-dose bolus i.v. 5-fluorouracil (5-FUra), 500 mg/sq m, and assayed for 5-fluorodeoxyuridylate (FdUMP), deoxyuridylate (dUMP), total thymidylate synthetase (TS), and non-FdUMP-bound, free enzyme. Nineteen patients had cancer of gastrointestinal origin, 13 of these colorectal, and 2 patients had breast adenocarcinoma. In 9 patients, synchronous biopsies of surgically normal liver were obtained along with samples of hepatic tumors metastatic from gastrointestinal sites. Total TS averaged 4.18 pmol/g in the malignant tissues and 2.23 pmol/g in liver. FdUMP levels in the gastrointestinal tumors were higher than in normal liver, were highest at the earliest time interval studied, 20 to 30 min, and appeared to decrease exponentially through 120 min. TS inhibition averaged 70 to 80% in gastrointestinal tumor biopsies and less than 50% in normal liver. Levels of dUMP were low and varied little with time. Those gastrointestinal tumors with higher FdUMP:dUMP ratios showed significantly greater TS inhibition. Tumors of 3 patients who benefited from 5-FUra therapy (1 patient with colonic adenocarcinoma and the 2 patients with breast adenocarcinoma) showed greater TS inhibition than did tumors of remaining patients. It is concluded that the apparent time course changes observed in FdUMP, dUMP, and TS in the grouped data are qualitatively similar to findings of murine studies in vivo and that the relationship between FdUMP:dUMP ratios and TS inhibition are consistent with established in vitro enzymic kinetics. Thus, biopsies of tumors at short time periods after 5-FUra administration may be usefully studied for biochemical parameters of TS inhibition, with the objectives of correlation of sensitivity to subsequent 5-FUra therapy and clarification of mechanisms of drug resistance.

Chemical cystitis and systemic toxic effects limit the therapeutic use of intravesical cytotoxic agents against bladder tumors. In our series 1,000 mg. 5-fluorouracil could be instilled 2 hours daily, 5 days per week for 5 weeks if 100 mg. allopurinol were given 3 times daily simultaneously. After 6 weeks all patients were macroscopically free of tumors. Another instillation was performed because of recurrences within 6 months in 3 patients. This preliminary report of 5 patients with multiple superficial transitional cell bladder tumors shows that a combined treatment of high dose 5-fluorouracil instillation and simultaneous oral allopurinol will abolish temporarily all tumor tissue without signs of general absorption or chemical cystitis. The observation time is too short to predict definitive cure.

During continuous systemic or portal infusion of 5-fluorouracil (5-FU) to anaesthetized pigs, the cytostatic activity was reduced in blood traversing the liver. The liver eliminated between 15 and 50% of the amount 5-FU given per time unit. During jugular infusion the concentration of cytostatic compounds in portal blood was equal to or less than in systemic blood. The cytostatic activity was much higher in portal blood and lower in systemic blood during portal infusion. The findings speak in favour of portal infusions of 5-FU to patients with disseminated cancer in the liver.

The survival of 47 patients with liver malignancies treated with continuous portal infusion of fluorouracil (5-FU) has been studied. 18 of them had been treated initially by hepatic artery ligation. Total mean survival was 9.4 months. Patients treated with hepatic artery ligation + 5-FU lived longer (mean 10.8 months) than those treated with 5-FU alone (7.4 months). The survival was longer than could be expected for patients treated for primary liver cancer or for liver metastases from colo-rectal cancer, when compared with the "untreated" group. It is concluded that continuous portal infusion of 5-FU appears to prolong survival in some groups of patients with malignant liver tumours. However, the influence of "unspecific, general" therapy is difficult to evaluate.

Theoretically, administration of 5-fluorouracil (5-FU) into the hepatic artery should improve the clinical response rate by high tumor cell extraction of the drug. However, previous studies in animals and man have also found a major extrahepatic elimination route for 5-FU. In the present study of 7 patients with primary and secondary liver cancer, we have found indications that a considerable elimination of 5-FU takes place in the cardio-pulmonary circuit. Thus, the mean AUC in the hepatic vein was 7185 mumol X min X l-1 and 3792 in a peripheral vein.

The effect of combined treatment with local hyperthermia and i.v. infusion of 5-fluorouracil was studied in 39 Wistar rats with a transplanted adenocarcinoma inoculated in the liver. Ten to 13 days later the rats were divided into three groups. Group A1 was subjected to local microwave hyperthermia (42 degrees C) for 1 h. During the hyperthermia, an i.v. infusion of 5-FU (20 mg/kg body weight) was given. In group A2 5-FU was administered under normothermic conditions. Group A3 received saline infusion under normothermic conditions. The mortality after infusion of 5-fluorouracil and hyperthermia increased during the first week after treatment. In group A1, a significant growth retardation of liver tumor was registered seven days after treatment. This effect was not superior to that of hyperthermia alone as previously described for the same experimental model. Studies of 5-FU pharmacokinetics in plasma were performed in another 20 Wistar rats. Ten rats were given an i.v. infusion of 5-FU during local hyperthermia, while the other 10 were infused under normothermic conditions. Plasma concentration of 5-FU was determined by isotachophoretic separation. The hyperthermia caused a faster decline in serum concentration of 5-FU, probably because of accelerated catabolism of the drug.

Thymidylate synthase (TS) is the enzyme target of 5-fluorouracil (FUra) that recent laboratory and clinical studies with folinic acid (calcium leucovorin) suggest may mediate important antitumor cytotoxicity. Measurement in carcinoma tissue of parameters related to TS inhibition by 5-fluorodeoxyuridylate (FdUMP), by analogy to hormone receptor analysis, should be useful to determine which patients should receive fluoropyrimidine drug therapy and to evaluate folinic acid requirements. Folinic acid is metabolized to 5,10-methylenetetrahydropteroylglutamine (CH2FH4), which must be present in large excess to effect desired levels of maximal inhibition of TS, by promoting formation and stabilization of TS-FdUMP-CH2FH4 ternary complexes. In patients with metastatic disease, serial biopsies of tumor and normal tissues for studies of pharmacodynamic responses to test-dose FUra or folinic acid are shown to be easily added to routine intraoperative management. A suitable methodologic approach is described and examples given of assays of free TS, FdUMP, dUMP, and CH2FH4 levels after FUra or folinic acid, that may be useful in future studies aimed at improving the cost-effectiveness of FUra-folinic acid combinations.

A microbiological agar plate technique for estimation of 5-fluorouracil concentrations in blood, urine and bile from man, dog and pig was evaluated. Different bacterial test strains, media modifications and techniques for inoculation were studied. The strain Streptococcus faecalis ATCC 8043, recommended previously by Clarkson et al., was found to be the most suitable. The influence of prediffusion, dilution, antibiotics and chemotherapeutic agents and their antagonists, as well as the effect of storage of samples containing 5-fluorouracil were examined. A detailed methodological description is presented. The method seems to be sufficiently sensitive and practical for routine determination of cytotoxic compounds from 5-fluorouracil in serum, plasma and urine.

The serum and urinary concentrations of 5-FU after continuous portal and jugular infusion have been followed by means of a highly sensitive microbiological assay method. Our data indicate that more than 90% of 5-FU was eliminated in the liver after continuous portal infusion of 0.625 mg x kg-1 x hr-1, corresponding to a dose of 15 mg x kg-1 x 24 hr-1. Negligible amounts of intact 5-FU were excreted into the bile, and the urinary excretion was only a few percent of the amount infused. The arterial concentration was on average tenfold higher during the continuous jugular infusion than after the continuous portal infusion, indicating that the route of administration has a pronounced effect on the disposition of 5-FU. Twenty-three percent of the jugular dose reached the liver; 77% was degraded by extrahepatic metabolism. Of these, degradation in the prehepatic splanchnic area accounted for 15%.