Factors that influence the therapeutic activity of 5-fluorouracil [6RS]leucovorin combinations in colon adenocarcinoma xenografts

Relationship between folate concentration and expression of folate-associated genes in tissue and plasma after intraoperative administration of leucovorin in patients with colorectal cancer

Purpose

The aim of study was to investigate the relationship between folate concentration and expression of folate-associated genes in tumour, mucosa and plasma of patients with colorectal cancer, after intraoperative administration of bolus leucovorin (LV).

Methods

Eighty patients were randomized into four groups to receive 0, 60, 200, or 500 mg/m² LV, respectively. Tissue and plasma folate concentrations were assessed by LC–MS/MS. Gene expression of ABCC3/MRP3, FPGS, GGH, MTHFD1L, SLC46A1/PCFT, and SLC19A1/RFC-1 was determined using quantitative PCR.

Results

The folate concentration in tumour increased with increasing dosage of LV. Half of the patients treated with 60 mg/m² did not reach a level above the levels of untreated patients. A significant correlation between folate concentration in tumour and mucosa was found in untreated patients, and in the group treated with 60 mg/m² LV. The 5-MTHF/LV ratio correlated negatively with folate concentration in mucosa, whereas a positive correlation was found in tumour of patients who received 200 or 500 mg/m² LV. A positive correlation was found between folate concentration and expression of all genes, except MTHFD1L, in patients who received LV. There was a negative correlation between 5-MTHF concentration in plasma of untreated patients and expression of GGH and SLC46A1/PCFT in tumour.

Conclusions

The results indicate the possibility of using the individual plasma 5-MTHF/LV ratio after LV injection as a surrogate marker for tissue folate concentration. Expression of several folate-associated genes is associated with folate concentration in tissue and plasma and may become useful when predicting response to LV treatment.

Electronic supplementary material

The online version of this article (10.1007/s00280-018-3690-9) contains supplementary material, which is available to authorized users.

Effects of the leucovorin shortage: Pilot study investigating cost, efficacy, and toxicity comparison of low fixed-dose versus body surface area-adjusted leucovorin dosing in patients with resectable colon or metastatic colorectal cancer

Purpose As a result of the leucovorin shortage, we switched from BSA-adjusted to low fixed-dose leucovorin in patients with colon cancer receiving fluorouracil-containing therapy. Methods A retrospective, pilot study of adults receiving intravenous leucovorin as part of a fluorouracil-containing treatment was conducted including individuals with stage II or III colon or newly diagnosed metastatic colorectal cancer. One low fixed-dose (leucovorin 50 mg) patient was matched by the investigator to one BSA-adjusted (leucovorin 200-500 mg/m²/dose) patient on disease stage and age. The objectives were to compare cost of alternative dosing strategies as well as efficacy and adverse event rates. Only patients being treated in the first-line metastatic colorectal cancer setting were included in the efficacy analysis. Results Fifty-eight patients were included. Leucovorin cost was reduced by 7- to 14-fold, and we were able to conserve a total of 1580-3400 doses of leucovorin by changing to fixed-dose (estimated from 200 mg/m² or 400 mg/m² dosing strategies, respectively). No statistically significant differences in progression-free survival ( p = 0.254), overall survival ( p = 0.923), or complications resulted. Conclusion Our decision to reduce the dose of leucovorin allowed us to conserve supply and control cost. The small sample size did not allow us to detect differences in efficacy or adverse event rates, and thus a larger study would be required to confirm our findings that efficacy was not compromised nor adverse effects greater.

Severe sequence-specific toxicity when capecitabine is given after Fluorouracil and leucovorin

PURPOSE

Options for single-agent fluoropyrimidine adjuvant therapy after bowel cancer resection include intravenous fluorouracil with leucovorin (FU/LV) or oral capecitabine. These treatments have similar efficacy but differ in convenience and toxicity. We therefore wished to compare their overall acceptability to patients.

PATIENTS AND METHODS

Patients scheduled for adjuvant single-agent fluoropyrimidine therapy were randomly assigned to receive once-weekly FU/LV (425 mg/m(2) FU, 45 mg LV) for 6 weeks, followed by two 3-week cycles of capecitabine (1,250 mg/m(2) twice daily, days 1 through 14), or the same treatments but in reverse order. After 12 weeks, the patients were asked which treatment they preferred, and received the preferred treatment for an additional 12 weeks. The primary end point was patient preference.

RESULTS

After 40 of the planned 74 patients had been randomly assigned, real-time adverse event monitoring led to early trial closure because of excess sequence-specific toxicity. Eleven of 14 patients (79%) receiving capecitabine as their second treatment experienced grade >/= 3 toxicity. This compared with five of 18 patients (28%) receiving capecitabine as the first treatment, and no patients receiving FU/LV as the first treatment (zero of 16) or the second treatment (zero of 12). Similar imbalances were seen in the proportion of patients requiring interruption of treatment.

CONCLUSION

In chemotherapy-naïve patients, capecitabine produced more toxicity than FU/LV, but at levels in line with previously reported data. However, treatment with capecitabine after FU/LV caused markedly increased toxicity, indicating a sequence-specific interaction. The mechanism has not been determined, but interaction with intracellularly retained folate after FU/LV therapy is a possibility. Oncologists need to be aware of this risk if considering crossing patients over from FU/LV to capecitabine-based regimens.

Response to 5-fluorouracil chemotherapy is modified by dietary folic acid deficiency in Apc(Min/+) mice

5-Fluorouracil (5-FU) has been the foundation of advanced colorectal cancer treatment for over 40 years. The Apc(Min/+) mouse, which is genetically predisposed to intestinal neoplasia, was used to examine the effects of 5-FU in this system and the impact of dietary folic acid on those effects. 5-FU treatment resulted in a 60-80% reduction in tumor number. Clinically relevant toxicities, including myelosuppression and mucositis, are a part of this response. Tumor numbers rebounded completely following termination of 5-FU therapy, indicating that the drug inhibits tumor growth but does not eradicate them. In mice that were fed with a defined diet containing no folic acid (0 ppm), 5-FU not only induced regression of pre-existing tumors, but also inhibited tumor recovery following drug withdrawal. Our data indicate that a dietary folic acid deficiency, in promoting tumor regression and inhibiting tumor recovery, may enhance the therapeutic effects of 5-FU.

A comprehensive review of 5-fluorouracil and leucovorin in patients with metastatic colorectal carcinoma

BACKGROUND

Colorectal carcinoma is the third leading cause of cancer-related death. The primary treatment for patients with metastatic colorectal carcinoma is systemic chemotherapy with 5-fluorouracil (5-FU) and leucovorin (LV), a biomodulator of 5-FU that has been shown to enhance its activity. Optimal dosing and administration strategies remain to be determined.

METHODS

This article is a review of recent studies reporting on the use of high dose and low dose LV as a biomodulator of 5-FU in patients with advanced colorectal carcinoma.

RESULTS

Studies of LV plus 5-FU demonstrated response rates of 7-58% in patients who had not received prior chemotherapy. A survival advantage was recorded in some trials. LV plus 5-FU produces mild and transient hematologic toxicity. The most common toxicities from LV plus 5-FU were gastrointestinal and schedule-dependent, but generally resolved within a few days.

CONCLUSIONS

The combination of LV and 5-FU provides a favorable treatment regimen for patients with metastatic colorectal carcinoma. Growing evidence suggests that altering the dose and schedule of both LV and 5-FU can impact positively on the response rate. However, controversy remains regarding the optimal dosing regimen. Therefore, continued study of LV plus 5-FU is urged and a favorable impact on survival is requisite before definitive conclusions are drawn, particularly in relation to LV dosage.

Relevance of tumoral folylpolyglutamate synthetase and reduced folates for optimal 5-fluorouracil efficacy: experimental data

The purpose of this study was to investigate folate-related predictors of 5-fluorouracil (5-FU) cytotoxicity in the presence or absence of l-folinic acid (l-FA). Intracellular concentrations of the reduced folates (tetrahydrofolate + 5,10-methylenetetrahydrofolate) and folylpolyglutamate synthetase (FPGS) activity were determined in 14 human cancer cell lines expressing a spontaneous sensitivity to 5-FU. On these 14 cell lines grown without l-FA supplementation, a significant positive correlation was demonstrated between basal intracellular folate concentration and FPGS activity. 5-FU sensitivity (IC50 range 0.6-25.4 microM) was not related to the basal intracellular folate concentration, whereas, significantly, it was linked to FPGS activity (range 2.5-11.1 pmol/min/mg protein): the higher the FPGS activity, the greater the 5-FU sensitivity. Under l-FA supplementation (0.01-300 microM), intracellular reduced folates increased continuously without evidence of saturation in all cell lines; the pattern of accumulation was independent of the FPGS activity. l-FA enhanced 5-FU cytotoxicity by a factor of 1.9-6.4 in 12 of the 14 cell lines. In the 12 FA-sensitive cell lines, the l-FA concentrations allowing 90% of maximum 5-FU potentiation [l-FA]90 ranged between 0.7 and 107.9 micro M (median 1.9); in contrast, the intracellular concentrations of reduced folates allowing 90% of maximum 5-FU potentiation were much less variable (range 7.6-38.3, median 24.8 pmol/mg protein). In the presence of [l-FA]90, 5-FU sensitivity remained significantly correlated to the basal FPGS activity. In addition, reduced folates were measured in 96 tumoral samples (50 head and neck, 16 colon, 30 liver metastases from colorectal cancer) taken before treatment. Almost all investigated tumours had folate concentrations below the median concentration required for optimal 5-FU potentiation in vitro: median levels (range, pmol/mg protein) were 3.8 (0-17.7) for head and neck, 5.8 (2.3-12.0) for colon and 12.1 (1.7-118.5) for liver metastases. Above all, these data establish the relevance of FPGS activity for predicting the efficacy of 5-FU modulated by FA or not and point to the potential clinical interest of FPGS determination in human tumours.

Impact of schedule on leucovorin potentiation of fluorouracil antitumor activity in dietary folic acid deplete mice

A dietary folic acid depleted mouse model was established and used to evaluate the relationship between elevation of reduced folates after leucovorin (LV) administration and potentiation of fluorouracil (FU) response of an implanted tumor. C3H mouse mammary adenocarcinomas from mice maintained on a folic acid deplete diet had modestly decreased methylenetetrahydrofolate and tetrahydrofolate levels, and were somewhat less responsive to FU alone compared with replete animals. LV administration resulted in a substantial increase in tumor folate by 1 hr that returned to near basal levels by 12 hr. Reduced folates were elevated to a lesser extent in animals on a standard diet. Tumor growth was suppressed approximately 80% when FU was administered to depleted animals 1 hr after LV administration, compared with approximately 50% suppression in control mice. LV administered 12 hr before FU resulted in tumor growth stimulation that was consistent with the pronounced growth stimulation when LV was administered without FU. These results show that dietary folic acid depletion can lead to a more responsive FU/LV model and that administration of LV at an improper time before FU not only can fail to potentiate but also can result in tumor growth stimulation.

Critical factors for optimizing the 5-fluorouracil-folinic acid association in cancer chemotherapy

BACKGROUND

The 5-fluorouracil (FU)-folinic acid (FA) association has demonstrated clinical efficacy in colorectal cancer, both in adjuvant and metastatic situations. However, there is no clear consensus about the optimal FU-FA schedule and dose. In addition, it would be of interest to identify FU-FA-responsive tumors.

DESIGN

Our purpose was to review preclinical and clinical data dealing with prediction of FU-FA sensitivity and optimization of FU-FA schedules.

RESULTS

Preclinical studies have highlighted the importance of thymidylate synthase (TS), the cellular target of the FU-FA mechanism of action, for predicting FU sensitivity. It appears that the more sensitive cell lines express the lowest TS activity. Interestingly, the cell lines sensitive to FA supplementation are those more sensitive to FU. The role of TS in FU-FA responsiveness has been clearly demonstrated in patients with colorectal and gastric cancers. Preliminary in vitro and clinical data have shown that the folylpolyglutamate synthetase (FPGS), the enzyme responsible for folate polyglutamylation, is another promising tool for identifying FU-FA-responsive tumors. So far, results of clinical trials do not form a clear consensus regarding the need to administer high FA doses for improving FU-FA treatment. Experimental studies on human cancer cell lines have demonstrated the wide variability among cell lines, ranging from 0.05 to 200 microns, of 1 FA concentrations required for maximal FU potentiation. In addition, pharmacokinetic studies have reported a significant variability of active folates in plasma after administration of standard-dose FA. Altogether, these observations favour high-dose FA administration to achieve high folate concentrations in plasma and thus to counteract the variability of the 1 FA concentrations required. With respect to the choice of FU-FA schedule, it appears from experimental data that increasing the duration of exposure to FA enhances FU-FA cytotoxicity, probably through an increased formation of reduced folate polyglutamate forms. Considering the S-phase specificity of FU cytotoxicity as well as its rapid elimination from plasma, a schedule of prolonged exposure to both FU and FA should be considered preferable.

CONCLUSIONS

Results of the new FU-FA administration schedules such as the one consisting of a 2-hour FA administration followed by a combination of FU bolus and FU infusion, or the chronomodulated FU-FA infusion, open up promising approaches for improving the therapeutic index of FU-FA chemotherapy. Finally, future clinical studies should investigate tumoral parameters pharmacologically linked to FU-FA sensitivity such as pre-treatment TS and FPGS activities. Such tumoral investigations along with FU and FA pharmacokinetic investigations should provide a better understanding of inter-patient variability in response to FU-FA therapy and an optimal management of this chemotherapy regimen.

Role of leucovorin dosing and administration schedule

Leucovorin (LV) is commonly administered in association with 5-fluorouracil (5-FU) to enhance its cytotoxic effects. In this paper, the cellular and clinical pharmacology of 5-FU potentiation by LV are reviewed, and the dosing and administration schedules are discussed in relation to reported clinical trials. In vitro experimental data suggest that prolonged cellular exposures to relatively low LV concentrations simultaneously with prolonged 5-FU administration are the optimal conditions to enhance 5-FU efficacy. Clinical studies of 5-FU/LV in metastatic colorectal carcinoma have established that 5-day bolus 5-FU with low-dose bolus LV injections yield therapeutic benefits equivalent to those obtained with intravenous bolus schedules using higher doses of LV. It remains to be determined, however, if bolus administration schedules are the optimal clinical treatment regimens. Infusional 5-FU/LV regimens appear to be a strategy worthy of further clinical investigation.

The effect of different routes of administration of 5-fluorouracil on thymidylate synthase inhibition in the rat

A rat colon tumour model of liver metastases was used to administer 5-fluorouracil (5FU) by intraperitoneal (i.p.) bolus injection (50 mg/kg), isolated liver perfusion (ILP, 150 mg/kg) and hepatic artery infusion (HAI, 50 mg/kg). The biochemical effect of 5FU, delivered by different routes, on its target enzyme thymidylate synthase (TS) was studied in both tumour and normal tissues of the rat. In tumour tissue, only small differences were observed in the extent of TS inhibition. A pronounced inhibition of TS was observed 3 h after 5FU administration by all routes, but was followed by a recovery of TS activity within 24 and 48 h. Effects of 5FU on normal tissues were diverse. In liver, TS activity increased 6-fold after ILP and HAI administration of 5FU, and a 2-fold increase of FdUMP binding to TS was seen for all routes of administration. In intestinal mucosa, both induction of TS activity (by ILP) and inhibition of TS activity (by HAI) were observed, while i.p. injection did not cause major changes. TS activity and FdUMP binding to TS in bone marrow was strongly inhibited after administration of 5FU by all routes, but administration by ILP seemed slightly advantageous, since a smaller extent of TS inhibition was observed compared to the other routes of administration. 5FU given by ILP had a small antitumour effect in this colon tumour model, while HAI administration had no antitumour activity. Since this difference in antitumour activity could not be related to differences in TS inhibition in the tumour, the RNA-directed mechanism of action of 5FU could be involved. Focusing on the effects of TS, we may conclude that the ILP administration of 5FU offered the important advantage of a lack of severe TS inhibition in normal tissues, which corresponds with the low systemic toxicity observed.

New targets for pyrimidine antimetabolites in the treatment of solid tumours. 1: Thymidylate synthase

Thymidylate synthase forms the target for anticancer therapy with fluoropyrimidines. Anticancer activity can be increased by the use of different modulators of fluoropyrimidine metabolism, which lead to an enhanced inhibition of thymidylate synthase. In vitro and in vivo studies with fluoropyrimidines and two of these modulators, folinic acid (leucovorin) and interferon, are summarized. The promise of these preclinical results is reflected by the response data of several clinical trials. The biochemical effects of these modulators are described and illustrated by the fluoropyrimidine-mediated inhibition of thymidylate synthase in tumour samples, which is clearly enhanced by folinic acid. The regulation of thymidylate synthase synthesis may also be crucial for total blockade of thymidylate synthase activity. This regulation may be influenced by interferon-gamma. Although the addition of modulators increases the activity of fluoropyrimidines at the level of thymidylate synthase, most solid tumours, especially colorectal carcinomas, are resistant to these combinations. For this reason, new, more potent inhibitors of thymidylate synthase have been developed, the antifolates. Preclinical data show that some of these compounds have good antitumour activity, but they still have to prove their value in the clinic. These two approaches, the use of modulators and new compounds, have shown activity preclinically and the extension of these findings to clinical studies stresses the importance of thymidylate synthase as a target in fluoropyrimidine therapy of solid tumours.

Wide range for optimal concentration of folinic acid in fluorouracil modulation--experimental data on human tumour cell lines

The clinical use of the fluorouracil (FU)-folinic acid (FA) combination is hampered by the still open choice of the optimal schedule, with marked controversy as concerns the optimal FA dose. This in vitro study on FU-FA combinations in 17 human cancer cell lines, representative of tumour types responding to FU-FA treatment, reassesses the notion of the optimal FA concentration. Cells were exposed for 5 days to various FU-FA concentrations (0.07-77 microM, 14 concentrations, for FU; and 0.0025-100 microM for FA). The growth inhibition was assessed by the MTT test. The investigated cell lines exhibited FU IC50 ranging from 0.4 to 38.9 microM (median 3.7 microM). In six out of 17 cell lines investigated, the addition of FA did not result in a substantial enhancement of FU cytotoxicity (group 1). For the remaining 11 cell lines responding to FA supplementation (group 2), the maximal enhancement factor ranged from 3 to 8, meaning that in the presence of optimal FA concentration, the efficient FU concentration (IC50) was reduced by between 3 and 8 as compared to the efficient FU concentration without FA supplementation. For cell lines responding to FA supplementation, the optimal FA concentrations ranged from 10(-7) to 4 x 10(-4) M (4000-fold range) with a median value at 9.6 x 10(-7) M. Distribution of cell doubling time was not significantly different between group 1 and group 2. In contrast, the FU IC50 were significantly different (P = 0.02) between group 1 (median 7.4 microM) and group 2 (median 2.2 microM), thus indicating that cell lines with the greatest FU cytotoxicity enhancement by FA were those intrinsically sensitive to FU and vice versa.