Biochemical and clinical aspects of methotrexate neurotoxicity

Iron(III) chloride hexahydrate does not enhance methotrexate cytotoxicity on Saccharomyces cerevisiae

Methotrexate is a potent inhibitor of dihydropholate reductase that has been used as effective antineoplastic treatment due to its capacity to inhibit cell growth. In a previous work published in Bioelectrochemistry 2003;60:81-86, we reported a statistically significant increment of 40.1 and 29.4% in methotrexate potency when MCF-7 breast cancer cells were exposed simultaneously to iron(III) chloride hexahydrate (FeCl(3).6H(2)O) and methotrexate. The aim of this study was to investigate whether iron(III) could produce, on a Saccharomyces cerevisiae wild-type strain, alterations on methotrexate potency by the drop test survival assay and proliferation studies measured after 24 and 96 h of exposure. The data presented in the current report indicate that FeCl(3).6H(2)O (1, 10, 100 and 500 microg/ml) does not induce modulation of the action of methotrexate (10, 100 and 500 microg/ml) in S. cerevisiae yeast cells when they are exposed simultaneously for 24 and 96 h.

Methotrexate-immobilized poly(ethylene glycol) magnetic nanoparticles for MR imaging and drug delivery

We report the development of a biostable methotrexate-immobilized iron oxide nanoparticle drug carrier that may potentially be used for real-time monitoring of drug delivery through magnetic resonance imaging. Methotrexate (MTX) was immobilized on the nanoparticle surface via a poly(ethylene glycol) self-assembled monolayer (PEG SAM). The cytotoxicity of the nanoparticle-drug conjugate (NP-PEG-MTX) to target cells was studied with 9L glioma cells. Cellular uptake experiments showed that the uptake of NP-PEG-MTX conjugates by glioma cells was considerably higher than that of control nanoparticles. Magnetic resonance imaging in 9L cells cultured with NP-PEG-MTX of various concentrations showed significant contrast enhancement. NP-PEG-MTX demonstrated higher cytotoxicity in 9L cells to free MTX in vitro. Leucovorin, an MTX antidote, was used to rescue the cells that had been exposed to NP-PEG-MTX or free MTX, and the experiment verified the biocompatibility of NP-PEG-MTX conjugates and the MTX on NP-PEG-MTX conjugates to be the true source of the cytotoxicity to the target cells. TEM results showed that NP-PEG-MTX conjugates were internalized into the 9L cellular cytoplasm and retained its crystal structure therein for up to 144 h, as identified by electron diffraction. This prolonged particle retention may allow physicians to image tumor cells exposed to the NP-PEG-MTX conjugate over an extended therapeutic time course.

The Activities of Antioxidant Enzymes and the Level of Malondialdehyde in Cerebellum of Rats Subjected to Methotrexate: Protective Effect of Caffeic Acid Phenethyl Ester

Methotrexate (MTX), a folic acid antagonist, is widely used as a cytotoxic chemotherapeutic agent. MTX-associated neurotoxicity is an important clinical problem. The aim of this study was to investigate the role of caffeic acid phenethyl ester (CAPE) on cerebellar oxidative stress induced by MTX in rats. A total of 19 adult male rats were divided into three experimental groups as follows: MTX group (MTX treated), MTX+CAPE group (MTX+CAPE treated), and control group. MTX was administered intraperitoneally (i.p.) with a single dose of 20 mg kg(-1) on the second day of experiment. CAPE was administered i.p. with a dose of 10 micromol kg(-1) day(-1) for 7 days. Malondialdehyde (MDA) levels and activities of superoxide dismutase (SOD) and catalase (CAT) were determined in cerebellar tissue of rats. MTX caused to significant increase in MDA levels (an important marker of lipid peroxidation) in the MTX group compared with the controls (p = 0.006). CAPE significantly reduced the MTX induced lipid peroxidation in the MTX+CAPE group compared to the MTX (p = 0.007). The activities of SOD and CAT were significantly increased in the MTX group when compared with the control group (p = 0.0001, p = 0.004, respectively). The increased activities of these enzymes were significantly reduced by CAPE treatment (p = 0.004, p = 0.034, respectively). As a result, CAPE may protect from oxidative damage caused by MTX treatment in rat cerebellum.

Diffusion-weighted MRI correlates of subacute methotrexate-related neurotoxicity

OBJECTIVES

A delayed stroke-like leukoencephalopathy has been observed in patients receiving methotrexate (MTX) for childhood leukemia. Diffusion-weighted MRI (DWI) may help to distinguish between ischemic stroke and chemotherapy-related leukoencephalopathy. Although conventional MRI correlates have been described for this stroke-like syndrome, DWI data are largely unavailable. Our objective is to present a retrospective analysis of the DWI findings in four patients who suffered subacute neurotoxicity after intrathecal MTX.

DESIGN

We reviewed the medical records of four patients, who were seen by us between July 2000 and February 2004 for sudden onset of a central neurological syndrome within days of intrathecal MTX. Patients underwent standardized MRI within 48 h of symptom onset; MRI included DWI and apparent diffusion coefficient (ADC) maps.

RESULTS

DWI of all patients revealed well-demarcated hyperintense lesions within the subcortical white matter corresponding to areas of restricted proton diffusion on ADC maps. Lesions exceeded the confines of adjacent vascular territories. Complete resolution of symptoms within 1-4 days was accompanied by normalization of ADC abnormalities.

CONCLUSIONS

DWI findings in this cohort seem to reflect cytotoxic edema within cerebral white matter suggesting a reversible metabolic derangement, rather than ischemia, as the basis for this syndrome.

Diffusion-weighted MRI correlates of subacute methotrexate-related neurotoxicity

OBJECTIVES

A delayed stroke-like leukoencephalopathy has been observed in patients receiving methotrexate (MTX) for childhood leukemia. Diffusion-weighted MRI (DWI) may help to distinguish between ischemic stroke and chemotherapy-related leukoencephalopathy. Although conventional MRI correlates have been described for this stroke-like syndrome, DWI data are largely unavailable. Our objective is to present a retrospective analysis of the DWI findings in four patients who suffered subacute neurotoxicity after intrathecal MTX.

DESIGN

We reviewed the medical records of four patients, who were seen by us between July 2000 and February 2004 for sudden onset of a central neurological syndrome within days of intrathecal MTX. Patients underwent standardized MRI within 48 h of symptom onset; MRI included DWI and apparent diffusion coefficient (ADC) maps.

RESULTS

DWI of all patients revealed well-demarcated hyperintense lesions within the subcortical white matter corresponding to areas of restricted proton diffusion on ADC maps. Lesions exceeded the confines of adjacent vascular territories. Complete resolution of symptoms within 1-4 days was accompanied by normalization of ADC abnormalities.

CONCLUSIONS

DWI findings in this cohort seem to reflect cytotoxic edema within cerebral white matter suggesting a reversible metabolic derangement, rather than ischemia, as the basis for this syndrome.

Neuropsychological function in high-risk breast cancer survivors after stem-cell supported high-dose therapy versus standard-dose chemotherapy: evaluation of long-term treatment effects

BACKGROUND

Studies on cognitive functioning in breast cancer patients point out that a subset of women exhibit chemotherapy-related neuropsychological impairment. Thereby, high-dose therapy may elevate the risk of cognitive dysfunctions. The primary purpose of the study was to evaluate the impact of high-dose versus standard-dose chemotherapy on the late neuropsychological outcome in randomized assigned high-risk breast cancer survivors. Next to focusing prevalence, function specificity and extent of cognitive impairment, the question as to whether doses-dependent group differences occur was investigated.

PATIENTS AND METHODS

Twenty-four high-dose and 23 standard-dose patients 5 years, on average, after treatment underwent a comprehensive neuropsychological assessment. In addition, 29 early-stage breast cancer patients matched for age, education and time since treatment were recruited as a comparison group.

RESULTS

Global cognitive impairment was observed in 8% of high-dose versus 13% of standard-dose compared with 3% of early-stage breast cancer patients. Compared with normative data, all patient groups performed worse on one attention subtest measuring the simple reaction time (P < 0.001 in each case). By contrast, no significant between-group differences on the late neuropsychological outcome were found.

CONCLUSIONS

Five years after treatment, standard-dose patients were slightly, but not significantly, more impaired in cognitive performance than high-dose patients.

Delayed neurotoxicity associated with therapy for children with acute lymphoblastic leukemia

Most children diagnosed today with acute lymphoblastic leukemia (ALL) will be cured. However, treatment entails risk of neurotoxicity, causing deficits in neurocognitive function that can persist in the years after treatment is completed. Many of the components of leukemia therapy can contribute to adverse neurologic sequelae, including craniospinal irradiation, nucleoside analogs, corticosteroids, and antifolates. In this review, we describe the characteristic radiographic findings and neurocognitive deficits seen among survivors of childhood ALL. We summarize what is known about the pathophysiology of delayed treatment-related neurotoxicity, with a focus on the toxicity resulting from pharmacologic disruption of folate physiology within the central nervous system. Finally, we suggest testable strategies to ameliorate the symptoms of treatment-related neurotoxicity or decrease its incidence.

Whole brain magnetization transfer histogram analysis of pediatric acute lymphoblastic leukemia patients receiving intrathecal methotrexate therapy

BACKGROUND AND PURPOSE

The purpose of this prospective study was to evaluate the hypothesis that magnetization transfer ratio (MTR) histogram analysis of the whole brain could detect early and subtle brain changes nonapparent on conventional magnetic resonance imaging (MRI) in children with acute lymphoblastic leukemia (ALL) receiving methotrexate (MTX) therapy.

MATERIALS AND METHODS

Subjects in this prospective study comprised 10 children with ALL (mean age, 6 years; range, 0-16 years). In addition to conventional MRI, magnetization transfer images were obtained before and after intrathecal and intravenous MTX therapy. MTR values were calculated and plotted as a histogram, and peak height and location were calculated. Differences in peak height and location between pre- and post-MTX therapy scans were statistically analyzed. Conventional MRI was evaluated for abnormal signal area in white matter.

RESULTS

MTR peak height was significantly lower on post-MTX therapy scans than on pre-MTX therapy scans (p = 0.002). No significant differences in peak location were identified between pre- and post-chemotherapy imaging. No abnormal signals were noted in white matter on either pre- or post-MTX therapy conventional MRI.

CONCLUSIONS

This study demonstrates that MTR histogram analysis allows better detection of early and subtle brain changes in ALL patients who receive MTX therapy than conventional MRI.

Prognostic factors in primary central nervous system lymphomas

Efforts to identify survival predictors in primary central nervous system lymphoma (PCNSL) have produced isolated, unconfirmed observations in small retrospective and prospective series. Age and performance status are two unanimously accepted prognostic factors. These and other independent predictors of survival were used by the International Extranodal Lymphoma Study Group (IELSG) to establish a prognostic scoring system able to distinguish risk groups in PCNSL. The IELSG score will improve further with better knowledge of these malignancies, especially with the inclusion of molecular and pharmacogenetic variables able to identify lymphomas with different chemosensitivities or degrees of aggressiveness. In the years ahead, a well-established prognostic score will allow the separation of patients into risk groups, which could result in the application of risk-tailored therapeutic strategies.

Treatment-related neurotoxicity

Two challenges need to be addressed to improve the outcome of patients with primary central nervous system lymphoma. The first challenge is to develop therapies that result in less toxicity and improved long-term outcome. The second challenge is to develop interventions to help those patients who develop treatment-related neurotoxicity; ongoing collaborative efforts are required to improve communication and understanding of this complication. Long-term follow up of prospective therapeutic studies should report on both disease control and the development of neurotoxicity. New protocols should include prospective longitudinal measures of neurocognitive function.

Pharmacodynamic properties of methotrexate and Aminotrexate during weekly therapy

4-Amino-pteroyl-glutamic acid (Aminotrexate; AMT) has several advantages over the related antifolate methotrexate (MTX), including greater potency, complete oral bioavailability, and greater accumulation by leukemic blasts in vitro. We compared the pharmacodynamic properties of AMT (given orally at 4 mg/m2 in two divided doses per week) and MTX (100 mg/m2 in four divided doses per week) among children with acute lymphoblastic leukemia. We find AMT and MTX to have equivalent penetration into the bone marrow compartment of these patients, as indicated by the steady-state concentrations within mature red blood cells (RBCs). However, MTX concentrations in the cerebrospinal fluid after oral dosage are significantly greater than AMT. To confirm these clinical observations, mice were treated four weekly injections of AMT or MTX, at a 1:20 dosage ratio, and tissue antifolate content was then determined over the subsequent 22 days. We confirm the selective exclusion of AMT from the CNS compartment, while showing equivalent accumulation of AMT and MTX in the RBCs, liver, spleen, kidneys and testes. Finally, we demonstrate that AMT, MTX, and their predominant polyglutamate species are equipotent inhibitors of their target intracellular enzyme dihydrofolate reductase, emphasizing the critical nature of steady-state tissue accumulation in determining the relative cytotoxic potency of these two antifolates.

Visuomotor control in survivors of childhood acute lymphoblastic leukemia treated with chemotherapy only

Treatment for childhood acute lymphoblastic leukemia (ALL), which includes CNS prophylaxis, is associated with central and peripheral neurotoxicity. The purpose of the present study was to analyze the effects of chemotherapy on various levels of visuomotor control in survivors of childhood ALL treated without cranial irradiation, and to identify risk factors for possible deficits. Visuomotor function was compared between children after treatment for ALL (n = 34), children after treatment for Wilms tumor, which consists of non-CNS directed chemotherapy (n = 38), and healthy controls (n = 151). Three tasks were administered: a simple visual reaction time task and two tasks measuring visuomotor control with one requiring a higher level of cognitive control than the other. Visuomotor deficits were detected only in the ALL group, with poorer performance restricted to the condition requiring the highest level of control. Significant risk factors for poorer performance were female gender and a short time since end of treatment, and a trend was found for a young age at diagnosis. A high cumulative methotrexate dose was an adverse predictive factor in girls. The results indicate that chemotherapy-induced central neurotoxicity in childhood ALL treatment is associated with higher order visuomotor control deficits. Girls appear to be particularly vulnerable.

Approaching an individual methotrexate regimen in leptomeningeal carcinomatosis

BACKGROUND

Chemotherapeutic effects in leptomeningeal carcinomatosis (LC) vary widely between patients, presumably in part because drug elimination from cerebrospinal fluid (CSF) differs between individuals. An individual dosing, adapted to elimination, may improve treatment efficacy.

OBJECTIVE

To discuss the feasibility of easily accessible elimination parameters for an individual dosing of chemotherapy in LC.

MATERIALS AND METHODS

The elimination of intrathecally applied methotrexate (Mtx) was tested in 14 LC patients and compared to the literature data. Plasma drug levels and CSF albumin levels are suggested as elimination parameters.

RESULTS AND DISCUSSION

Mtx disappeared from CSF and appeared in plasma with an expected wide variation (interindividual range of coefficients of variation (CV) of CSF Mtx levels 158-189%, intraindividual range of CV of plasma Mtx levels 35-64%). Our data together with reported data suggest that plasma Mtx levels mirror closely the Mtx elimination from CSF. The levels of CSF albumin and of plasma Mtx at defined sample times correlated negatively (r=-0.7), which reflects their largely common elimination from CSF.

CONCLUSION

Both parameters seem appropriate to describe the Mtx elimination from CSF. They should allow to individually adapt Mtx dosing towards an improvement of Mtx availability in CSF and of treatment efficacy.

Acute Cardiac Toxicity Associated with High-Dose Intravenous Methotrexate Therapy: Case Report and Review of the Literature

A 36-year-old woman was hospitalized for preoperative chemotherapy for osteosarcoma. She received intravenous fluids for 12 hours for volume expansion, then methotrexate 24 g (12 g/m2) over 6 hours. This was followed by intravenous leucovorin 200 mg over 1 hour. Two hours after the methotrexate infusion the patient developed chest pain and bradycardia. An electrocardiogram revealed sinus pauses, and telemetry recordings indicated a 4-beat run of ventricular tachycardia. A cardiac work-up consisting of cardiac enzyme level determination, two-dimensional echocardiography, and an adenosine technetium-99m tetrofosmin stress test was negative for structural and ischemic heart disease. The patient recovered without treatment and, approximately 2 weeks later, received a second course of methotrexate at half the dose without complication. One month later the patient received treatment with doxorubicin and cisplatin; 2 days later she died unexpectedly at home. Clinicians should be aware that high-dose methotrexate can cause cardiac symptoms and arrhythmias in previously healthy adults. This complication warrants attention and needs additional clinical investigation.

Intrathecal methotrexate neurotoxicity: clinical correlates and antidotal treatment

The neurotoxicity of methotrexate (MTX) is more severe when administered intrathecally (IT) than by the oral and intravenous (IV) routes, and has been reported even with a single administration of therapeutic doses of 12 or 15mg. Prompt recognition and treatment are essential to improve the outcome after massive IT-MTX overdose. Treatment options include CSF drainage or CSF exchange, ventriculolumbar perfusion, IT corticosteroids to reduce CSF inflammation and IV leucovorin to reduce systemic toxicity. Toxicity resulting from IT injection of leucovorin is controversial. CSF drainage and exchange are particularly effective if performed soon after the overdose. In this paper we describe a protocol of treatment for severe cases of IT-MTX overdose in excess of 100mg. The mainstay of treatment is dilution and removal from CSF of excessive methotrexate alongside with specific antidotal therapy.

Homocysteine: exploring its potential as a pharmacodynamic biomarker of antifolate chemotherapy

For decades it has been well known that elevated levels of homocysteine are harmful to humans on the basis of clinical observations derived from classical model diseases, such as inherited metabolic disorders. This group of diseases includes classical homocystinuria and several other inherited diseases affecting the so-called 'transsulfuration pathways'. Homocysteine lies in a metabolic checkpoint that interconnects one-carbon-transferring reactions with metabolism of sulfur-containing amino acids, since every molecule of 5-methyltetrahydrofolate derived either from plasma or generated from other folate species must be demethylated to liberate the reduced tetrahydrofolate. This unidirectional mechanism operates in every cell and has no alternative in eukaryotic cells. Antifolates are a group of anticancer agents targeting various metabolic steps within folate metabolism. They exert an indirect influence on the rate of appearance/disappearance of homocysteine from cellular and plasma compartments. Recently, it has been postulated that homocysteine may be a marker of the 'pharmacodynamic effect' of methotrexate, but studies attesting to this role are only now emerging. Here, we explore the genetic disease of folate and homocysteine metabolism and discuss the links between these model disorders with pharmacology and pharmacogenetics of folate antagonists used in the clinic. We outline possible ways of how homocysteine may be used as a biomarker of antifolate therapy.

Treatment of early childhood medulloblastoma by postoperative chemotherapy alone

BACKGROUND

The prognosis for young children with medulloblastoma is poor, and survivors are at high risk for cognitive deficits. We conducted a trial of the treatment of this brain tumor by intensive postoperative chemotherapy alone.

METHODS

After surgery, children received three cycles of intravenous chemotherapy (cyclophosphamide, vincristine, methotrexate, carboplatin, and etoposide) and intraventricular methotrexate. Treatment was terminated if a complete remission was achieved. Leukoencephalopathy and cognitive deficits were evaluated.

RESULTS

Forty-three children were treated according to protocol. In children who had complete resection (17 patients), residual tumor (14), and macroscopic metastases (12), the five-year progression-free and overall survival rates (+/-SE) were 82+/-9 percent and 93+/-6 percent, 50+/-13 percent and 56+/-14 percent, and 33+/-14 percent and 38+/-15 percent, respectively. The rates in 31 patients without macroscopic metastases were 68+/-8 percent and 77+/-8 percent. Desmoplastic histology, metastatic disease, and an age younger than two years were independent prognostic factors for tumor relapse and survival. Treatment strategies at relapse were successful in 8 of 16 patients. There were no major instances of unexpected toxicity. In 19 of 23 children, asymptomatic leukoencephalopathy was detected by magnetic resonance imaging. After treatment, the mean IQ was significantly lower than that of healthy controls within the same age group but higher than that of patients in a previous trial who had received radiotherapy.

CONCLUSIONS

Postoperative chemotherapy alone is a promising treatment for medulloblastoma in young children without metastases.

Effects of intraventricular methotrexate on folate, adenosine, and homocysteine metabolism in cerebrospinal fluid

Methotrexate (MTX) is an antifolate that affects many metabolic pathways. MTX may cause neurologic toxicity, but the biochemical effects of MTX on the central nervous system (CNS) are poorly characterized. The authors studied serial cerebrospinal fluid (CSF) samples from a child during two courses of intraventricular MTX and found a rapid and reproducible depletion in CSF of reduced folates and S-adenosylmethionine that was accompanied by marked increases in homocysteine and adenosine. No sulfur-containing excitatory amino acids were detected. This study demonstrates multiple profound effects of MTX on CNS metabolism and provides insight to the pathogenesis of MTX neurotoxicity.

Fatal Acute Encephalomyelitis After a Single Dose of Intrathecal Methotrexate

A 40-year-old Hispanic man with acute lymphoblastic leukemia was treated with a single dose of intrathecal methotrexate 12 mg for prophylaxis against leptomeningeal spread of tumor. The day after methotrexate administration, the patient complained of severe back pain and urinary retention. The diagnosis of encephalomyelitis was made on day 3 after methotrexate administration, and by day 6 mechanical ventilation was begun secondary to ascending paralysis. By day 8 the patient was comatose, with minimal signs of brain activity and little hope for recovery; on day 12 he died. Although neurotoxicity is a frequent complication of methotrexate therapy, fatal acute neurotoxicity is extremely uncommon, especially in adults. The mechanisms of methotrexate toxicity remain unclear, and no effective treatment exists to prevent its occurrence. This patient rapidly progressed from mild neurotoxicity to fatal encephalopathy after one dose of intrathecal methotrexate during his third cycle of chemotherapy. Clinicians should be aware of the signs and symptoms of neurotoxicity during treatment, as well as predisposing factors that put patients receiving methotrexate at risk for neurotoxic effects.

Genetic and Plasma Markers of Venous Thromboembolism in Patients with High Grade Glioma

PURPOSE

Deep venous thrombosis/pulmonary embolism (DVT/PE) is a frequent complication in the course of cancer, particularly in brain tumors. We investigated genetic and plasma factors possibly associated with risk of DVT/PE in patients with high-grade glioma.

EXPERIMENTAL DESIGN

In a case-control study, we studied polymorphisms of the genes coding for factor II (G20210A), factor V (G1691A), methylenetetrahydrofolate-reductase (C677T), tissue-type plasminogen activator (tPA; insertion/deletion), plasminogen activator inhibitor-1 (PAI-1; 4G/5G), and vascular endothelial growth factor (VEGF; C936T). We also measured plasma levels of D-dimer, lipoprotein (lp) (a), homocysteine, VEGF, tPA, and PAI-1, comparing healthy control patients with patients with glioma or with patients with neurological nonneoplastic disease (multiple sclerosis).

RESULTS

Genotype frequencies of polymorphisms analyzed were similar in patients with glioma and in healthy matched population. D-dimer, lp (a), homocysteine, VEGF, tPA, and PAI-1 plasma levels were significantly higher in patients with glioma than in healthy controls, whereas patients having neurological nonneoplastic disease had plasma values of these molecules not significantly different from healthy controls. VEGF, tPA, and PAI-1 were also found at high-plasma levels in patients carrying genotypes that, in healthy controls, were associated with "low-producing" phenotypes.

CONCLUSIONS

Genetic risk factors alone did not explain the high incidence of DVT/PE observed in patients with glioma. Higher plasma levels of molecules influencing the coagulation pathways indicate that the tumor itself might confer an increased risk of DVT/PE; thus, D-dimer, homocysteine, lp (a), VEGF, tPA, and PAI-1 look like good candidates to be evaluated as DVT/PE prognostic factors.