Effect of dose and repeat intravenous 24 hr infusions of methotrexate on cerebrospinal fluid availability in children with hematological malignancies

Predicting delayed methotrexate elimination in pediatric acute lymphoblastic leukemia patients: an innovative web-based machine learning tool developed through a multicenter, retrospective analysis

BACKGROUND

High-dose methotrexate (HD-MTX) is a potent chemotherapeutic agent used to treat pediatric acute lymphoblastic leukemia (ALL). HD-MTX is known for cause delayed elimination and drug-related adverse events. Therefore, close monitoring of delayed MTX elimination in ALL patients is essential.

OBJECTIVE

This study aimed to identify the risk factors associated with delayed MTX elimination and to develop a predictive tool for its occurrence.

METHODS

Patients who received MTX chemotherapy during hospitalization were selected for inclusion in our study. Univariate and least absolute shrinkage and selection operator (LASSO) methods were used to screen for relevant features. Then four machine learning (ML) algorithms were used to construct prediction model in different sampling method. Furthermore, the performance of the model was evaluated using several indicators. Finally, the optimal model was deployed on a web page to create a visual prediction tool.

RESULTS

The study included 329 patients with delayed MTX elimination and 1400 patients without delayed MTX elimination who met the inclusion criteria. Univariate and LASSO regression analysis identified eleven predictors, including age, weight, creatinine, uric acid, total bilirubin, albumin, white blood cell count, hemoglobin, prothrombin time, immunological classification, and co-medication with omeprazole. The XGBoost algorithm with SMOTE exhibited AUROC of 0.897, AUPR of 0.729, sensitivity of 0.808, specificity of 0.847, outperforming the other models. And had AUROC of 0.788 in external validation.

CONCLUSION

The XGBoost algorithm provides superior performance in predicting the delayed elimination of MTX. We have created a prediction tool to assist medical professionals in predicting MTX metabolic delay.

An intrathecal limited postoperative chemotherapy regimen for the treatment of young children with nodular/desmoplastic medulloblastoma and medulloblastoma with extensive nodularity

PURPOSE

Therapy for medulloblastoma in patients < 4 years old omits radiotherapy due to anticipated neurocognitive deficits. The German Pediatric Brain Tumor Study Group described a chemotherapy regimen (HIT-SKK' 92 and HIT-SKK 2000) without radiation which yielded a 5-year progression-free survival (PFS) rate of 85% in children with nodular/desmoplastic medulloblastoma (NDMB) and medulloblastoma with extensive nodularity (MBEN). We modified the HIT-SKK regimen to reduce the total number of intrathecal methotrexate (IT MTX) doses from 12 to 2 doses/cycle and obviate Ommaya reservoir implantation through the use of lumbar administration. We report the outcomes of five patients treated with our approach.

METHODS

IT MTX was eliminated altogether on weeks when high-dose intravenous methotrexate was administered. On weeks when no systemic methotrexate was administered, a single dose of lumbar-administered IT MTX was substituted in place of multiple intra-Ommaya doses. Cumulative dosing of MTX was 16-24 mg/cycle (age-based) compared to 24 mg/cycle in the HIT-SKK regimen. Following chemotherapy, patients were monitored with interval imaging, observation for acute and late effects, and survival.

RESULTS

Four children remained in remission 3, 5, 9, and 10 years post-treatment respectively, without observed learning difficulties. One child had recurrent tumor and metastasis 6 months post-treatment. She failed the attempted salvage regimen and continued to deteriorate, dying of disease at 3 years old.

CONCLUSIONS

Review of existing literature supported our modifications well. While this report is limited by the small number of children treated, we believe there is encouraging evidence that our approach warrants further evaluation in a larger population of young children with NDMB and MBEN.

Histone deacetylase inhibition enhances the therapeutic effects of methotrexate on primary central nervous system lymphoma

Background

Polyglutamylation is a reversible protein modification that commonly occurs in tumor cells. Methotrexate (MTX) in tumor cells is polyglutamylated and strongly binds to dihydrofolate reductase (DHFR) without competitive inhibition by leucovorin. Therefore, tumor cells with high polyglutamylation levels are supposed to be selectively killed, whereas normal cells with lower polyglutamylation are rescued by leucovorin. This study investigated the combined effects of MTX plus histone deacetylase inhibitors (HDACIs), which upregulate MTX polyglutamylation, in primary central nervous system lymphoma (PCNSL).

Methods

We evaluated cell viability after MTX treatment and leucovorin rescue and compared the expression of folylpolyglutamate synthetase (FPGS), γ-glutamyl hydrolase (GGH), and DHFR in 2 human PCNSL-derived cell lines (HKBML and TK) and a human Burkitt lymphoma cell line (TL-1). Combination treatments were created using 4 HDACIs: panobinostat, vorinostat, sodium butyrate, and valproic acid. The expression of DHFR was examined as well as ratios of FPGS/GGH expression. The combined effects of MTX plus HDACIs were evaluated using a cell viability assay, mass spectroscopy imaging, and subcutaneous and intracranial xenograft models.

Results

HDACIs upregulated the ratio of FPGS/GGH expression resulting in increased polyglutamylation of MTX, but also downregulated expression of the target molecule of MTX: DHFR. The combination of MTX and vorinostat decreased cell viability in vitro (P < .05) and tumor volumes in a subcutaneous model (P < .0001), and prolonged survival in an intracranial model (P < .01), relative to controls.

Conclusion

HDACIs enhanced the therapeutic effect of MTX through increased polyglutamylation of MTX and concomitant downregulation of DHFR expression.

Rituximab in patients with primary CNS lymphoma (HOVON 105/ALLG NHL 24): a randomised, open-label, phase 3 intergroup study

BACKGROUND

The prognosis for primary CNS lymphoma has improved with the use of high-dose methotrexate-based chemotherapy, but patient outcomes remain poor. Rituximab, a chimeric monoclonal antibody that targets the CD20 cell surface protein, has substantial activity in systemic CD20-positive diffuse large B-cell lymphoma, but its efficacy in primary CNS lymphoma is unknown and low penetration of the large rituximab molecule through the blood-brain barrier could limit its effect. We aimed to investigate the addition of rituximab to a high-dose methotrexate-based chemotherapy regimen in patients with newly diagnosed primary CNS lymphoma.

METHODS

This intergroup, multicentre, open-label, randomised phase 3 study was done at 23 hospitals in the Netherlands, Australia, and New Zealand. Non-immunocompromised patients aged 18-70 years with newly diagnosed primary CNS lymphoma were randomly assigned (1:1) to receive methotrexate-based chemotherapy with or without intravenous rituximab. We used a web-based randomisation system with stratification by centre, age, and Eastern Cooperative Oncology Group-WHO performance status, and a minimisation procedure. All group assignment was open label and neither investigators nor patients were masked to allocation. All patients were treated with two 28-day cycles of induction chemotherapy, consisting of intravenous methotrexate 3 g per m² on days 1 and 15, intravenous carmustine 100 mg per m² on day 4, intravenous teniposide 100 mg per m² on days 2 and 3, and oral prednisone 60 mg per m² on days 1-5, with (R-MBVP) or without (MBVP) intravenous rituximab 375 mg per m² on days 0, 7, 14, and 21 in cycle one and days 0 and 14 in cycle two. Patients with response at the end of induction subsequently received high-dose cytarabine and, in patients aged 60 years or younger, low-dose whole-brain radiotherapy. The primary endpoint was event-free survival, with events defined as not reaching complete response or complete response unconfirmed at the end of treatment, or progression or death after response; analysis was adjusted for age and performance score. Patients were analysed on a modified intention-to-treat basis. This trial is registered with the Nederlands Trial Register, number NTR2427, and the Australian New Zealand Clinical Trials Registry, number ACTRN12610000908033. The trial was closed on May 27, 2016, after achieving complete accrual, and follow-up is ongoing.

FINDINGS

Between Aug 3, 2010, and May 27, 2016, we recruited 200 patients (109 men and 91 women; median age was 61 years [IQR 55-67]). We randomly assigned 100 patients to MBVP and 99 patients to R-MBVP. One patient was randomly assigned to the R-MBVP group but found to be ineligible because of an incorrect diagnosis and was excluded from all analyses. After a median follow-up of 32·9 months (IQR 23·9-51·5), 98 patients had had an event (51 in the MBVP group and 47 in the R-MBVP group), of whom 79 had died (41 in the MBVP group and 38 in the R-MBVP group). Event-free survival at 1 year was 49% (95% CI 39-58) in the MBVP group (no rituximab) and 52% (42-61) in the R-MBVP group (with rituximab; hazard ratio 1·00, 95% CI 0·70-1·43, p=0·99). Grade 3 or 4 adverse events occurred in 58 (58%) patients in the MBVP group and 63 (64%) patients in the R-MBVP group, with infections (24 [24%] patients receiving MBVP vs 21 [21%] patients receiving R-MBVP), haematological toxicity (15 [15%] vs 12 [12%]), and nervous system disorders (ten [10%] vs 15 [15%]) being the most common. Life-threatening or fatal serious adverse events occurred in 12 (12%) patients in the MBVP group and ten (10%) patients in the R-MBVP group, and five (5%) patients in the MBVP group and three (3%) in the R-MBVP group died from treatment-related causes.

INTERPRETATION

We found no clear benefit of addition of rituximab to methotrexate, carmustine, teniposide, and prednisone chemotherapy in primary CNS lymphoma. Therefore, the results of this study do not support the use of rituximab as a component of standard treatment in primary CNS lymphoma.

FUNDING

Roche, the Dutch Cancer Society, and Stichting STOPhersentumoren.

Blood-brain barrier, cytotoxic chemotherapies and glioblastoma

INTRODUCTION

Glioblastomas (GBM) are the most common and aggressive primary malignant brain tumors in adults. The blood brain barrier (BBB) is a major limitation reducing efficacy of anti-cancer drugs in the treatment of GBM patients. Areas covered: Virtually all GBM recur after the first-line treatment, at least partly, due to invasive tumor cells protected from chemotherapeutic agents by the intact BBB in the brain adjacent to tumor. The passage through the BBB, taken by antitumor drugs, is poorly and heterogeneously documented in the literature. In this review, we have focused our attention on: (i) the BBB, (ii) the passage of chemotherapeutic agents across the BBB and (iii) the strategies investigated to overcome this barrier. Expert commentary: A better preclinical knowledge of the crossing of the BBB by antitumor drugs will allow optimizing their clinical development, alone or combined with BBB bypassing strategies, towards an increased success rate of clinical trials.

Prediction of methotrexate CNS distribution in different species - influence of disease conditions

Children and adults with malignant diseases have a high risk of prevalence of the tumor in the central nervous system (CNS). As prophylaxis treatment methotrexate is often given. In order to monitor methotrexate exposure in the CNS, cerebrospinal fluid (CSF) concentrations are often measured. However, the question is in how far we can rely on CSF concentrations of methotrexate as appropriate surrogate for brain target site concentrations, especially under disease conditions. In this study, we have investigated the spatial distribution of unbound methotrexate in healthy rat brain by parallel microdialysis, with or without inhibition of Mrp/Oat/Oatp-mediated active transport processes by a co-administration of probenecid. Specifically, we have focused on the relationship between brain extracellular fluid (brainECF) and CSF concentrations. The data were used to develop a systems-based pharmacokinetic (SBPK) brain distribution model for methotrexate. This model was subsequently applied on literature data on methotrexate brain distribution in other healthy and diseased rats (brainECF), healthy dogs (CSF) and diseased children (CSF) and adults (brainECF and CSF). Important differences between brainECF and CSF kinetics were found, but we have found that inhibition of Mrp/Oat/Oatp-mediated active transport processes does not significantly influence the relationship between brainECF and CSF fluid methotrexate concentrations. It is concluded that in parallel obtained data on unbound brainECF, CSF and plasma concentrations, under dynamic conditions, combined with advanced mathematical modeling is a most valid approach to develop SBPK models that allow for revealing the mechanisms underlying the relationship between brainECF and CSF concentrations in health and disease.

Methotrexate concentrations in cerebrospinal fluid and serum, and the risk of central nervous system relapse in children with acute lymphoblastic leukaemia

The aim of the study was to characterize the relationship between the pharmacokinetics of methotrexate in serum and concentrations in the cerebrospinal fluid, and to analyse the association to risk of a central nervous system relapse in children with acute lymphoblastic leukaemia. In this retrospective study, 353 children with acute lymphoblastic leukaemia treated with high-dose methotrexate according to the Nordic Society of Pediatric Haematology and Oncology-92 acute lymphoblastic leukaemia protocol were studied. Data from 18 patients with a subsequent central nervous system relapse and 335 event-free patients were available. In 34 patients the methotrexate concentrations were monitored repeatedly during each 24-h methotrexate intravenous infusion and a cerebrospinal fluid sample was taken at the end of the infusion. Using statistics separating interindividual and intraindividual variability, methotrexate concentration in cerebrospinal fluid was found to be significantly dependent upon both serum concentrations at the end of infusion and the area under the concentration curve in serum (P<0.0017 and <0.002, respectively). The logistic regression analysis revealed that high patient median serum methotrexate concentrations at the end of infusion were significantly associated with decreased risk for a central nervous system relapse in the standard risk group (P=0.02) and the number of courses with a calculated cerebrospinal fluid concentration of more than 1 mumol/l (P=0.048) with a decreased risk of a central nervous system relapse in the combined (standard risk and intermediate) risk group. In conclusion, methotrexate concentrations in cerebrospinal fluid are dependent on methotrexate concentrations in serum and serum area under the concentration curve. Multivariate analysis indicates that an increased exposure to methotrexate is related to decreased risk for central nervous system relapse.

Chemotherapy delivery issues in central nervous system malignancy: a reality check

PURPOSE

This review assesses the current state of knowledge regarding preclinical and clinical pharmacology for brain tumor chemotherapy and evaluates relevant brain tumor pharmacology studies before October 2006.

RESULTS

Chemotherapeutic regimens in brain tumor therapy have often emerged from empirical clinical studies with retrospective pharmacologic explanations, rather than prospective trials of rational chemotherapeutic approaches. Brain tumors are largely composed of CNS metastases of systemic cancers. Primary brain tumors, such as glioblastoma multiforme or primary CNS lymphomas, are less common. Few of these tumors have well-defined optimal treatment. Brain tumors are protected from systemic chemotherapy by the blood-brain barrier (BBB) and by intrinsic properties of the tumors. Pharmacologic studies of delivery of conventional chemotherapeutics and novel therapeutics showing actual tumor concentrations and biologic effect are lacking.

CONCLUSION

In this article, we review drug delivery across the BBB, as well as blood-tumor and -cerebrospinal fluid (CSF) barriers, and mechanisms to increase drug delivery to CNS and CSF tumors. Because of the difficulty in treating CNS tumors, innovative treatments and alternative delivery techniques involving brain/cord capillaries, choroid plexus, and CSF are needed.

Treatment of CNS dissemination in systemic lymphoma

The frequency of central nervous system (CNS) dissemination in non-Hodgkin's lymphoma (NHL) varies and is dependent on NHL histology. More than 50% of patients with CNS involvement have advanced and progressive systemic disease. While CNS involvement at initial diagnosis may be treated curatively, treatment of CNS involvement in systemic relapsing or refractory lymphoma is challenging and most often palliative. Due to a paucity of randomized trials, treatment of lymphomatous metastases is not standardized. Nonetheless, treatment of LM entails administration of both CNS-directed and systemic chemotherapy that often includes high-dose chemotherapy regimens with stem cell support.

Implications of the blood–brain barrier in primary central nervous system lymphoma

✓ The optimal treatment of primary central nervous system lymphoma (PCNSL), a rare form of extranodal non-Hodgkin lymphoma, has yet to be defined. Whole-brain radiation therapy (WBRT) has limited efficacy as a single therapeutic modality and is associated with a high risk of delayed neurotoxicity. Methotrexate-based chemotherapy regimens yield poor drug penetration across the blood–brain barrier (BBB), thus necessitating administration of high doses with the concomitant risk of increased systemic and neurological toxicity. Combined-modality therapy (WBRT plus chemotherapy) can improve response and survival rates, yet it is associated with a high risk of neurotoxicity. The aim of chemotherapy in conjunction with BBB disruption is to maximize drug delivery to the brain and improve the agent's efficacy, while preserving neurocognitive function and minimizing systemic toxicity. Methotrexate-based chemotherapy regimens administered in conjunction with BBB disruption have shown promising results in PCNSL. Animal models of central nervous system lymphoma and drug neurotoxicity offer new possibilities to study the effects of various treatments on PCNSL and normal brain and can also help understand biological and pathophysiological aspects of this disease. Because the intact BBB is even less permeable to antibodies than it is to drugs, preclinical and clinical studies of monoclonal antibody delivery (for example, rituximab and 90Y ibritumomab tiuxetan) to the brain in conjunction with BBB disruption offer a new possibility to make these novel treatments more efficient against PCNSL. Regarding the evaluation of more sensitive and specific diagnostic imaging tools, iron oxide–based contrast agents for magnetic resonance imaging have shown promise for better differentiation of PCNSL from other white matter diseases.

High-dose methotrexate toxicity in elderly patients with primary central nervous system lymphoma

BACKGROUND

The dose of high-dose methotrexate (HDMTX) in elderly patients often has to be reduced, resulting in a loss of treatment efficacy. We evaluated HDMTX-related toxicity with special regard to age distribution in patients with primary central nervous system lymphoma (PCNSL) in a phase IV multicenter trial.

PATIENTS AND METHODS

One hundred and fifty-four patients (median age 61 years; 89 patients >60 years old, 21 patients >70 years old) received 619 HDMTX cycles. Toxicity was evaluated prospectively using the WHO classification. Unless a reduced dose was required after calculating a decreased glomerular filtration rate (GFR), the patients received 4 g/m(2) HDMTX followed by leucovorin rescue.

RESULTS

Toxicity was generally mild with toxicities of WHO grade > or =3 usually <10%. The differences in the incidence and severity of toxicity were not statistically significant between patients >60 years and < or =60 years old. The same was true for therapy termination owing to MTX toxicity and for delayed serum MTX clearance. Dose reduction significantly differed between patients < or =60 years and those >60 years old (18% versus 44%; P = 0.001).

CONCLUSIONS

HDMTX is a safe treatment for PCNSL patients regardless of age, with adherence to dose reduction determined by calculating the GFR before each treatment cycle.

Strategies for increasing drug delivery to the brain: focus on brain lymphoma

The blood-brain barrier (BBB) is a gate that controls the influx and efflux of a wide variety of substances and consequently restricts the delivery of drugs into the central nervous system (CNS). Brain tumours may disrupt the function of this barrier locally and nonhomogeneously. Therefore, the delivery of drugs to brain tumours has long been a controversial subject. The current concept is that inadequate drug delivery is a major factor that explains the unsatisfactory response of chemosensitive brain tumours. Various strategies have been devised to circumvent the BBB in order to increase drug delivery to the CNS. The various approaches can be categorised as those that attempt to increase delivery of intravascularly administered drugs, and those that attempt to increase delivery by local drug administration. Strategies that increase delivery of intravascularly injected drugs can manipulate either the drugs or the capillary permeability of the various barriers (BBB or blood-tumour barrier), or may attempt to increase plasma concentration or the fraction of the drug reaching the tumour (high-dose chemotherapy, intra-arterial injection). Neurotoxicity is a major concern with increased penetration of drugs into the CNS or when local delivery is practised. Systemic toxicity remains the limiting factor for most methods that use intravascular delivery. This review evaluates the strategies used to increase drug delivery in view of current knowledge of drug pharmacokinetics and its relevance to clinical studies of chemosensitive brain tumours. The main focus is on primary CNS lymphoma, as it is a chemosensitive brain tumour and its management routinely utilises specialised strategies to enhance drug delivery to the affected CNS compartments.

Cerebrospinal fluid concentrations of vincristine after bolus intravenous dosing: a surrogate marker of brain penetration

BACKGROUND

Vincristine (VCR) is used widely in oncology practice, and regular dosing is commonly associated with the development of sensorimotor or autonomic neuropathies. However, the incidence of VCR-related central nervous system (CNS) toxicity is comparatively low, suggesting that the blood-brain barrier may limit drug penetration into the brain parenchyma. This study determined whether measurable concentrations of VCR could be detected in the cerebrospinal fluid (CSF), as a surrogate marker of brain parenchyma penetration, after bolus intravenous injection in children without primary CNS pathology.

METHODS

The authors studied 17 pediatric patients ages 2.5-14.1 years (median, 6.8 years) with acute lymphoblastic leukemia or non-Hodgkin lymphoma without evidence of leptomeningeal disease. Patients received VCR 1.5 mg/m2 by intravenous bolus injection followed at varying intervals by lumbar puncture for scheduled intrathecal methotrexate administration under general anesthesia. Paired VCR concentrations in both plasma and CSF were measured in each patient simultaneously at times ranging from 8 minutes to 146 minutes after the VCR injection. Three patients were studied twice. The paired samples were stored at -40 degrees C until analysis using a high performance liquid chromatography assay with a sensitivity of 0.1 microg/L in CSF and 0.4 microg/L in plasma.

RESULTS

Plasma VCR concentrations ranged from 2.2 microg/L to 91.2 microg/L. No measurable VCR concentrations were detected in the CSF samples.

CONCLUSIONS

Measurable concentrations of VCR in CSF are not achieved after the administration of standard intravenous bolus doses of VCR. The current observations are consistent with the relative rarity of VCR-related CNS neurotoxicity compared with the commonly observed sensorimotor and autonomic neuropathies. These findings suggest that the penetration of VCR into the brain parenchyma of patients with a relatively intact blood-brain barrier is low and that VCR may have a limited role in the CNS-directed therapy of these patients.

Cerebrospinal fluid drug levels of leukemic children receiving intravenous 5 g/m2 methotrexate

A multicenter prospective study was conducted in 114 children with acute lymphoblastic leukemia receiving 4 intravenous methotrexate (MTX) courses (5 g/m2 as a 24 hour-infusion) to determine the diffusion of MTX in cerebrospinal fluid (CSF) and to correlate the drug levels to central nervous system (CNS) relapse occurrence. Serum and CSF levels were measured at the end of 446 MTX courses. A significant correlation was found between CSF and serum MTX concentration. CSF MTX level was greater than 1 mumol/l in 66% of the courses. Twelve patients (11%) failed to achieve this potentially cytotoxic drug level at the end of the 4 consecutive MTX courses: only one CNS relapse was observed and the mean age of these children was lower than that of the others. To date 9 (7.8%) children had CNS relapse and no difference was observed in terms of CSF MTX levels when compared to data of children free of CNS relapse. With a median follow up of 32 months, pharmacokinetic data during high-dose MTX therapy do not seem to be an exclusive predictive factor of CNS relapse.

2,4-diamino-7-hydroxy-pteridines in biological fluids of patients on high-dose methotrexate

Concentrations of 2,4-diamino-7-hydroxy-pteridines in plasma and cerebrospinal fluid (CSF) are reported for the 0.5-8 g/m2 dose range of methotrexate in children with acute lymphoblastic leukemia or non-Hodgkin's lymphoma. This experiment has revealed that: (1) there is a wide inter-individual but relatively narrow intra-individual variability of the maximal concentrations of 2,4-diamino-7-hydroxy-pteridines in plasma during consecutive methotrexate cycles; (2) the increase in the level of the metabolites in plasma was related to increments of the methotrexate dose, but not above 5 g/m2: this can be explained by a saturable conversion of methotrexate to 2,4-diamino-7-hydroxy-pteridines; (3) significant correlations were found between simultaneous values of 2,4-diamino-7-hydroxy-pteridines in plasma and CSF; (4) the formation of 2,4-diamino-7-hydroxy-pteridines did not depend on the ages of patients receiving the same dose of methotrexate. The presence of these compounds in plasma and CSF in significant amounts creates the potential for a number of competitive interactions with pteridine-dependent metabolism which may open up new possibilities for understanding the metabolic side-effects of methotrexate therapy.

CSF drug levels for children with acute lymphoblastic leukemia treated by 5 g/m2 methotrexate. A study from the EORTC Children's Leukemia Cooperative Group

A multicenter EORTC study was conducted in children with acute lymphocytic leukemia to determine whether 5 g/m2 of methotrexate (MTX) (24 h i.v. infusion, four cycles) is an appropriate dosage for obtaining CSF drug concentrations approaching the critical cytotoxic level of 10(-6) M. A total of 193 cycles were analyzed for 58 patients. At the end of the 24 h infusion, the mean MTX serum level was 65.27 +/- 33.11 microM; the mean CSF MTX level was 1.47 +/- 1.1 microM; no significant difference in CSF MTX levels was observed between patients with (n = 20) and those without i.v. Ara-C (n = 38). The mean CSF MTX/serum MTX ratio was 0.029 +/- 0.027. CSF drug concentrations greater than or equal to 10(-6) M were achieved in 81% of the courses. The highest level was 8.4 X 10(-6) M. Only 5% of patients failed to achieve this drug concentration in at least one cycle. No significant correlation was observed between blood and CSF MTX levels. Mean CSF MTX levels were comparable from one cycle to another.

Cerebrospinal fluid and plasma methotrexate levels following high-dose regimen given as a 3-hour intravenous infusion in children with nonHodgkin's lymphoma

In the French nonHodgkin's lymphoma protocols, central nervous system prophylaxis is provided by high-dose methotrexate (HD-MTX), given as a 3-hour IV infusion of 3 g/m2 MTX along with intrathecal MTX injection. The incidence of CNS relapse is less than 3%. We designed a study to evaluate the MTX transfer across the blood brain barrier in terms of cytotoxic concentrations, during these short-term infusions. Cerebrospinal fluid and plasma MTX levels were measured during 61 courses in 29 children with nonHodgkin's lymphoma; none of them had central nervous system disease. Samples were obtained either 4, 12, 18, or 24 hours after the start of HD-MTX IV infusion. A potentially cytotoxic MTX level (10(-6)M) was reached in all courses at 4 hours (median: 2.3 X 10(-6)M) and remained available in 8/16 courses at 12 hours (median: 1.0 X 10(-6)M) and in only 2/17 courses at 18 hours (median: 0.29 X 10(-6)M). Twenty-four hours after the start of HD-MTX IV infusion, CSF MTX level was always less than 10(-6)M. The plasma MTX levels were 260, 1.3, 1.0, and 1.7 X 10(-6)M at 4, 12, 18, and 24 hours, respectively. There was no correlation between plasma and CSF MTX levels. These data show that potentially cytotoxic MTX concentrations can be reached in CSF after a 3-hour IV infusion of 3 g/m2 in every patient and remain available for at least 8 hours in half of them.

Evidence for CSF accumulation of 5-methyltetrahydrofolate during repeated courses of methotrexate plus folinic acid rescue

In the first part of this study the availability of folinic acid (FA) and its main active circulating metabolite, 5-methyltetrahydrofolate (5-MTHF), were studied in plasma and cerebrospinal fluid (CSF) from normal subjects after i.v. administration of 100 and 250 mg of FA. 5-MTHF rapidly appeared in plasma, the maximum value being reached at the first observation time point (1 h). FA was eliminated in plasma more slowly than 5-MTHF. Between the two doses, there was no evidence of modification in pharmacokinetic parameters (terminal half-life, clearance) for either FA or 5-MTHF in plasma and CSF; 5-MTHF was the only product detectable in CSF. Considering FA plus 5-MTHF together, the AUC (area under the curve) ratios between CSF and plasma were close to 1%. 5-MTHF was cleared very slowly from CSF (t 1/2 = 85 h). This finding suggested possible accumulation of 5-MTHF in CSF during repeated administration of FA combined with medium or high dose MTX. In the second part of the study, dealing with a group of eight children treated by such protocols, an increase in CSF 5-MTHF was detected from cycle to cycle in five (r = 0.91, P less than 0.01) with a maximum at 5 x 10(-8) M. This progressive accumulation of 5-MTHF in CSF may have a negative effect on the local action of MTX and should be taken into account for therapeutic strategies designed for the management of meningeal leukaemia.