Neurotoxicity of antineoplastic agents

Aspects of vincristine-induced neuropathy in hematologic malignancies: a systematic review

PURPOSE

Vincristine is widely used as anticancer therapy for a variety of hematological malignancies. The treatment is limited by progressive vincristine-induced neuropathy, possibly including both peripheral sensory and motor nerves, autonomic nervous functions, and the central nervous system. This dose-limiting side-effect can diminish quality of life and, furthermore, cause discontinuation of vincristine treatment. The present review elucidates the current knowledge regarding vincristine-induced neuropathy in hematologic malignancies, focusing on neuropathy assessment, clinical and molecular predictive markers, drug-drug interference, prevention, and treatment.

METHODS

This review is conducted by a systematic search strategy for the identification of relevant literature in the PubMed and Embase databases.

RESULTS

No clinical parameters displayed convincing potential as predictors of vincristine-induced neuropathy; however, preexisting neuropathy was consistently reported to be associated with an increased risk of neurotoxicity. In contrast, molecular markers, including polymorphisms in genes involved in the pharmacodynamics and pharmacokinetics of vincristine, displayed great potential as predictive markers of neuropathy incidence and severity. Furthermore, antifungal drugs, such as itraconazole and voriconazole, decrease the metabolism of vincristine and consequently lead to severe neuropathy when co-administered with vincristine, underscoring why fluconazole should be the antifungal drug of choice.

CONCLUSION

Reports from the 71 included studies clearly emphasize the lack of consistency in neuropathy assessment, grading systems, and reporting, making it difficult to interpret results between studies. Thus, truer clinical and molecular markers could emerge if the consistency of neuropathy detection and reporting increases by the use of conventional standardized neuropathy assessment tools and grading scales.

A comprehensive model of the development of mental handicap in children treated for acute lymphoblastic leukaemia: A synthesis of the literature

Most clinical studies addressing sequelae in children with leukaemia are not theory-driven. Nonetheless, the role of different mediating biological (e.g. cranial irradiation, chemotherapy) and psychosocial variables (e.g. family functioning) has been empirically acknowledged. In these studies, a cause-effect relationship between biological variables and cognitive deficits, sometimes complex due to multiple agents, has been hypothesised. As for the psychosocial consequences, adaptation to the cancer-related stress has been the main focus, at both the individual and family levels. In this paper, we advocate the use of a global model for the development of handicap, derived from the International Classification of Impairments, Disabilities and Handicaps (ICIDH) by the World Health Organisation. This revised model proposes that handicap is the result of complex interactions between the characteristics of a person’s impairment, disabilities, and the characteristics of the environment. At each of these levels, risk/resilience factors are defined. This means that depending on the environmental obstacles they face, persons with an impairment or a disability may or may not experience a situation creating a handicap which is no longer seen as a stable status resulting from a disease to which the individual must adapt. By reviewing animal and clinical studies, current knowledge pertaining to leukaemia sequelae are integrated into the different levels defined by the model: organic impairment, disabilities, environmental obstacles, and handicap situation. Practical implications for research, policies, and individual treatments, and comparisons with existing models, are also outlined.

Toxic leukoencephalopathies, including drug, medication, environmental, and radiation-induced encephalopathic syndromes

Toxic leukoencephalopathies can be secondary to the exposure to a wide variety of exogenous agents, including cranial irradiation, chemotherapy, antiepileptic agents, drugs of abuse, and environmental toxins. There is no typical clinical picture, and patients can present with a wide array of signs and symptoms. Involvement of white matter is a key finding in this scenario, although in some circumstances other high metabolic areas of the central nervous system can also be affected. Magnetic resonance (MR) imaging usually discloses bilateral and symmetric white matter areas of hyperintense signal on T2-weighted and fluid-attenuated inversion recovery images, and signs of restricted diffusion are associated in the acute stage. In most cases, the changes are reversible, especially with prompt recognition of the disease and discontinuation of the noxious agent. Either the MR or clinical features may be similar to several nontoxic entities, such as demyelinating diseases, leukodystrophies, hepatic encephalopathy, vascular disease, hypoxic-ischemic states, and others. A high index of suspicion should be maintained whenever a patient presents recent onset of neurologic deficit, searching the risk of exposure to a neurotoxic agent. Getting to know the most frequent MR appearances and mechanisms of action of causative agents may help to make an early diagnosis and begin therapy, improving outcome. In this review, some of the most important causes of leukoencephalopathies are presented; as well as other 2 related conditions: strokelike migraine attacks after radiation therapy syndrome and reversible splenial lesions.

Pharmacokinetic evaluation of vincristine for the treatment of lymphoid malignancies

INTRODUCTION

Vincristine is a key agent for the treatment of acute lymphoblastic leukemia (ALL) and other lymphoid malignancies. The strong antineoplastic activity of vincristine has been limited by its pharmacological characteristics.

AREAS COVERED

This paper reviews the role of vincristine in the treatment of lymphoid malignancies. This review summarizes its efficacy and toxicity, and focuses on the pharmacokinetic features of vincristine that affect clinical outcomes.

EXPERT OPINION

As a single agent, vincristine is associated with brief and incomplete responses, but in combination with other agents, vincristine has dramatically improved the outcomes of lymphoid malignancies such as ALL. Vincristine is a key drug of hyper-fractionated cyclophosphamide, vincristine, doxorubicin and dexamethasone, an intensive chemotherapeutic regimen for the treatment of ALL, and of cyclophosphamid, adriamycin, vincristine and prednisone, which has been used extensively in the treatment of patients with aggressive or indolent lymphomas and Richter syndrome. The strong antileukemic activity of vincristine has been limited by its variable and unpredictable pharmacological characteristics, narrow therapeutic index and neurotoxicity profile. These characteristics prompted the development of liposomal vincristine, which has optimized its clinical application. Liposomal vincristine has promising antileukemic activity, and it is approved by the FDA as a single agent for the treatment of relapsed/refractory Philadelphia chromosome-negative ALL.

Indole molecules as inhibitors of tubulin polymerization: potential new anticancer agents

Agents that interfere with tubulin function have a broad anti-tumor spectrum and they represent one of the most significant classes of anticancer agents. In the past few years, several small synthetic molecules that have an indole nucleus as a core structure have been identified as tubulin inhibitors. Among these, several aroylindoles, arylthioindoles, diarylindoles and indolylglyoxyamides have shown good inhibition towards the tubulin polymerization. This article reviews the synthesis, biological activities and SARs of these main classes of indoles. Brief mention has also been made about the fused indole analogs as tubulin inhibitors.

A tubulin binding peptide targets glioma cells disrupting their microtubules, blocking migration, and inducing apoptosis

Despite aggressive treatment regimes, glioma remains a largely fatal disease. Current treatment limitations are attributed to the precarious locations within the brain where such tumors grow, their highly infiltrative nature precluding complete resection and lack of specificity among agents capable of attenuating their growth. Here, we show that in vitro, glioma cells of diverse origins internalize a peptide encompassing a tubulin-binding site (TBS) on the neurofilament light protein. The internalized peptide disrupts the microtubule network, inhibits migration and proliferation, and leads to apoptosis. Using an intracerebral transplant model, we show that most, if not all, of these responses to peptide exposure also occur in vivo. Notably, a single intratumor injection significantly attenuates tumor growth, while neither peptide uptake nor downstream consequences are observed elsewhere in the host nervous system. Such preferential uptake suggests that the peptide may have potential as a primary or supplementary glioblastoma treatment modality by exploiting its autonomous microtubule-disrupting activity or engaging its capacity to selectively target glioma cells with other cell-disrupting cargos.

Vinflunine: review of a new vinca alkaloid and its potential role in oncology

Objective: To review the pharmacology, pharmacokinetics, in vitro and in vivo efficacy, and safety profile of vinflunine in the treatment of various solid tumors.

Data sources: A literature search was conducted using keywords included vinflunine, vinca alkaloid, Javlor, and solid tumor in PubMed/MEDLINE (1950—January 2009) and International Pharmaceutical Abstracts (1950—January 2009). Study selection and data extraction: Published studies, posters, and meeting abstracts evaluating the in vitro and in vivo efficacy of vinflunine were reviewed.

Data synthesis: Vinflunine is the newest member of the vinca alkaloid family. It has the weakest affinity to tubulins, but is shown to have unique receptor-independent antiangiogenesis, and antimetastasis properties. After administration, it is distributed extensively into tissues, metabolized via the CYP3A4 system, and eventually excreted in urine and feces. Phase II/III trials reported activities of vinflunine in advanced stage nonsmall-cell lung cancer, metastatic breast cancer, metastatic renal cell carcinoma, transitional cell carcinomas of the urothelium, small-cell lung cancer, and malignant pleural mesothelioma as monotherapy and in combination with other chemotherapy agents. More ongoing trials are evaluating its use in other solid tumors and in combination regimens. The most common adverse events in these trials were hematological (anemia and neutropenia), constipation, fatigue, abdominal pain, and myalgia.

Conclusions: Vinflunine is a new vinca alkaloid for the treatment of advanced staged solid tumors. Available data showed promising activities in various malignancies. Further studies are needed to further define vinflunine’s role in oncology.

Medulloblastoma in childhood: revisiting intrathecal therapy in infants and children

INTRODUCTION

Intrathecal chemotherapy is being explored in medulloblastoma in pre-school children as part of brain-sparing strategies and as an alternative to unacceptably neurotoxic cranio-spinal radiotherapy. The range of drugs suitable for this route of administration is restricted by the lack of research evidence of pharmacological suitability and efficacy of other drugs in medulloblastoma.

METHODS

Ideal clinical, biological, physicochemical and pharmaceutical properties for intrathecal administration were defined through literature review of pharmaceutical texts, Medline, Embase and consulting the manufacturers. A total of 126 chemotherapy agents were assessed against these criteria by searching the academic domain of pharmaceutical texts, computer databases and consultation with manufacturers.

RESULTS

Of the 126 candidate drugs, 99 were rejected because of documentation of their irritant nature, neurotoxicity and requirement for hepatic activation in standard pharmaceutical texts. Fifty were rejected for a single identifiable reason including, neurotoxicity (n = 24), irritant (n = 15), needs enzyme activation (n = 5), clinical evidence of intrathecal neurotoxicity (n = 4) and no evidence of tumour-specific efficacy (n = 2). Where two reasons were cited the justifications were: neurotoxic and irritant (n = 3) and needs activation and systemic administration results in equivalent concentration (n = 1). Twenty-seven drugs remained of which 12 were selected as eligible for further clinical investigation, and 15 were selected for further pre-clinical investigation.

CONCLUSIONS

The pre-determined criteria were not applicable, in their entirety, in the majority of drugs, due to lack of information in the academic domain, emphasising the importance of a more open approach for sharing basic drug information. The prioritised list of 12 candidate drugs for clinical trial and 15 for pre-clinical investigation justify that a concerted research effort in this area of practice is made.

Dose-finding and pharmacokinetic study of orally administered indibulin (D-24851) to patients with advanced solid tumors

Indibulin (ZIO-301/D-24851) is an orally applied small molecule with antitumor activity based upon destabilization of microtubule polymerization. The purpose of this phase I study was to determine the maximum tolerated dose (MTD) as well as the dose limiting toxicity (DLT), the pharmacokinetics, safety and tolerability of orally administered indibulin as capsule formulation in patients with advanced solid tumors. Patients received a single dose of indibulin. Seven dose-levels were evaluated: 100 mg, 150 mg, 250 mg, 350 mg and 600 mg once daily (QD), 450 mg and 600 mg twice daily (BID). After a washout period, patients received indibulin at the pre-defined daily dose for 14 days every 3 weeks (multiple dose part). A total of 28 patients entered the study. Indibulin administered as capsules was generally well tolerated. The MTD was not reached. There was a disproportionate increase of the area under the plasma concentration-time curve (AUC) with dose, with declining AUC corrected for dose starting at the 250 mg dose-level. There was no significant difference in AUC of indibulin after multiple dosing (day 1-14) compared to single administration (day-4). Inter-patient variability in AUC (102% CV) was high. A plateau in drug exposure was observed prior to reaching the MTD. Continued dose-escalation was unlikely to yield any increase in exposure of indibulin. The formulation needs optimization to increase the systemic exposure upon oral administration.

Anticancer, neuroprotective activities and computational studies of 2-amino-1,3,4-thiadiazole based compound

Anticancer activity studies of 2-(4-fluorophenylamino)-5-(2,4-dihydroxyphenyl)-1,3,4-thiadiazole (FABT), as one of the most promising derivatives from the N-substituted 2-amino-5-(2,4-dihydroxyphenyl)-1,3,4-thiadiazole set, have been continued. The tested compound inhibited proliferation of tumor cells derived from cancers of nervous system (medulloblastoma/rhabdosarcoma, neuroblastoma, and glioma) and peripheral cancers including colon adenocarcinoma and lung carcinoma. The anticancer effect of FABT was attributed to decreased cell division and inhibited cell migration. Furthermore, in anticancer concentrations it exerted a trophic effect in neuronal cell culture and had no influence on viability of normal cells including astrocytes, hepatocytes, and skin fibroblasts. Moreover, a prominent neuroprotective activity of FABT was observed in the neuronal cultures exposed to neurotoxic agents like serum deprivation and glutamate. To determine probability of tautomeric transition and indicate potential sites of interactions of FABT molecule with the receptor, quantum-chemical calculations with the ab initio Hartree-Fock model were made.

Phase I dose-finding and pharmacokinetic trial of orally administered indibulin (D-24851) to patients with solid tumors

Indibulin is a synthetic small molecule which antitumor activity is based upon destabilization of microtubules. The primary study objectives were to determine the impact of fasted and fed condition on pharmacokinetic parameters, as well as the maximum tolerated dose of the oral drinking solution of indibulin administered once daily for 14 days every 3 weeks in patients with solid tumors. In the pilot food effect part, patients received a single dose of 20 mg indibulin on day-8 and -4, fasted or fed, in a randomized crossover design. In the dose-escalation part, patients received a single dose of indibulin on day-4. Three dose levels were evaluated: 20, 40 and 80 mg. After a washout period, patients received indibulin once daily for 14 days every 3 weeks (multiple dose part). Blood samples were collected in the pilot food effect- and in the dose escalation study. A total of 14 patients entered, of which 6 completed the food effect study. The ratio of indibulin (fed/fasted) in the food effect study for AUC(0-72) was estimated as 1.24 (P=0.082, 95%CI 0.96-1.41) and C(max) ratio was 0.89 (P=0.54, 95%CI 0.55-1.44). Interpatient variability was high. Higher peak plasma concentrations were reached under fasting conditions which was undesired regarding tolerability. Therefore the dose escalation study was continued under fed conditions. Dose limiting toxicities, nausea and vomiting, appeared to be related to the increased volume of the solvent lactic acid. This study is continued, evaluating indibulin administered as capsules on the recommended dose level of 60 mg daily for 14 days.

Anticancer agents are potent neurotoxins in vitro and in vivo

Neurotoxicity of anticancer agents complicates treatment of children with cancer. We investigated neurotoxic effects of common cytotoxic drugs in neuronal cultures and in the developing rat brain. When neurons were exposed to cisplatin (5-100 microM), cyclophosphamide (5-100 microM), methotrexate (5-100 microM), vinblastin (0.1-1 microM), or thiotepa (5-100 microM), a concentration-dependent neurotoxic effect was observed. Neurotoxicity was potentiated by nontoxic glutamate concentrations. The N-methyl-D-aspartate receptor antagonist MK 801 (10 microM), the AMPA receptor antagonists GYKI 52466 (10 microM) and NBQX (10 microM), and the pancaspase inhibitor Ac-DEVD-CHO (1 nM) ameliorated neurotoxicity of cytotoxic drugs. To investigate neurotoxicity in vivo, we administered to 7-day-old rats the following: cisplatin (5-15 mg/kg i.p.), cyclophosphamide (200-600 mg/kg i.p.), thiotepa (15-45 mg/kg), or ifosfamide (100-500 mg/kg) and their brains were analyzed at 4 to 24 hours. Cytotoxic drugs produced widespread lesions within cortex, thalamus, hippocampal dentate gyrus, and caudate nucleus in a dose-dependent fashion. Early histological analysis demonstrated dendritic swelling and relative preservation of axonal terminals, which are morphological features indicating excitotoxicity. After longer survival periods, degenerating neurons displayed morphological features consistent with active cell death. These results demonstrate that anticancer drugs are potent neurotoxins in vitro and in vivo; they activate excitotoxic mechanisms but also trigger active neuronal death.

Chemotherapy-evoked painful peripheral neuropathy

Vincristine and paclitaxel, two of the most effective drugs in the battle against cancer, produce a dose-limiting neurotoxicity that sometimes presents as a painful peripheral neuropathy. For the first time, investigators have been able to produce these chemotherapy-evoked painful peripheral neuropathies in the laboratory rat. These new models have already begun to elucidate the causes of the neuropathic pain associated with these antineoplastic drugs, which will now make it possible to search for effective ways to prevent and treat it.

Recent advances in the field of tubulin polymerization inhibitors

In recent years, enormous progress has been made in the field of tubulin targeting agents. Several companies and academic laboratories have entered this field and competition has become very strong. Nevertheless, clinically promising compounds often face substantial limitations, such as high systemic toxicity, poor water solubility and bioavailability, as well as complex synthesis and isolation procedures. As a drawback of established drugs, like paclitaxel or the vinca alkaloids, the outcome of cancer chemotherapy is often affected by the emergence of the multidrug resistance phenotype. Among the recently disclosed tubulin polymerization inhibitors, there are several interesting low molecular weight compounds with improved oral bioavailability and demonstrated activity against multi-drug resistance positive phenotypes. As documented by the imidazole-based combretastatin analogs, to name just one example, chemical optimization of a lead structure resulted in compounds with potent in vitro and in vivo activity along with appropriate pharmacodynamic and pharmacokinetic requirements for a potential therapeutic candidate. Currently, several compounds are undergoing Phase I or Phase II clinical trials, among them orally bioavailable sulfonamides or dolastatin 10. Several other compounds are close to entering Phase I trials. The purpose of this review is to focus on the most recent advances in tubulin polymerization inhibitors from a survey of the published patent literature and related publications between late 1999 and April 2002. However, biological data, especially for the inhibition of tubulin polymerization, obtained from different laboratories cannot easily be compared.

Analysis of handwriting of children during treatment for acute lymphoblastic leukemia

BACKGROUND

Children treated for acute lymphoblastic leukemia (ALL) often complain about handwriting problems.

PROCEDURE

Using a computerized writing task, we have prospectively studied the processes necessary for the production of handwriting movements in 11 children (5-12 years old) during treatment for ALL. Children were tested at time points closely related to the vincristine administration.

RESULTS AND CONCLUSIONS

Children treated for ALL drew slower, with longer pause durations and increased drawing pressure. Children were able to overcome the problems, except for a consistently increased drawing pressure. This increased drawing pressure may be an attempt of the children to obtain sufficient kinesthetic information and thus can be seen as an adequate adaptation mechanism in case of peripheral neuropathy due to the neurotoxic effects of vincristine. However, neurotoxic effects of other cytostatic drugs cannot be excluded.

Influence of age and comorbidities on the chemotherapeutic management of lung cancer

More than 60% of all patients with cancer are currently older than 65 years. Correspondingly, the peak of lung cancer incidence is reached in the age group between 75 and 80 years. As a consequence to this ageing patient population, three factors become of major importance for the chemotherapeutic management of lung cancer, namely functional status, age-specific phenomenon and the presence of comorbidities. While the functional status is dependent on physiological changes in organ function, ageing-specific phenomena include depression, alterations of mental status, reduced nutritional status and missing social support. Comorbidities frequently have a risk profile comparable to that of lung cancer. Clinical studies with a special focus on elderly patients are still rare. In small-cell lung cancer retrospective analyses have demonstrated that age alone is not a major prognostic factor compared to performance status, tumor stage or gender. Nevertheless elderly patients with lung cancer are still frequently excluded from clinical trials, and receive less optimal or even no chemotherapeutic treatment at all. Studies evaluating less aggressive treatment figured out that single agent therapy with etoposide is inferior compared to combination chemotherapy in patients with small cell lung cancer (SCLC). In elderly patients with non-small cell lung cancer (NSCLC), single agent treatment with vinorelbine plus 'Best Supportive Care' was significantly superior to 'Best Supportive Care (BSC)' alone; with respect to survival and symptom palliation.

Assessment of the older cancer patient

The correct assessment of a cancer patient is a key step in the treatment process. In older people, this assessment entails not only the patient's basic medical history and the standard cancer staging, but also much more comprehensive evaluation of the various facets of the patient's health and environment that may interfere with his or her therapy. Patient fitness for elective surgery, radiation therapy, and chemotherapy must be considered. Geriatricians have defined the relevant aspects of the general evaluation of the older person, and now this work is being adapted to cancer patients. This article reviews the various aspects of a comprehensive assessment applicable to the cancer patient in settings such as academic oncology programs, cooperative group studies, and private oncology practice.

Cisplatin-based therapy: a neurological and neuropsychological review

The present paper reviews research in the area of the broad-spectrum chemotherapeutic agent cisplatin (cis-diamminedichloro-platinum II) and examines the implications for clinical neuropsychology arising from the neurological disruption associated with cisplatin-based therapy. The paper begins with a brief review of cisplatin treatment in terms other than survival alone, and examines the side-effects and the potential central nervous system (CNS) dysfunction in terms of neurological symptoms and concomitant implications for neuropsychology. Two main implications for clinical neuropsychology arising from cisplatin therapy are identified. First, cisplatin therapy impacts upon the psychological well-being of the patient, particularly during and in the months following treatment. It is suggested that during this time, a primary role for neuropsychology is to focus upon the monitoring and the active enhancement of the patient's social, psychological and spiritual resources. Second, with regard to neurocognitive changes, the review suggests that (1) neurocognitive assessment may not yield stable results within 8 months following treatment and (2) while perceptual, memory, attentional and executive dysfunction may be predicted following cisplatin treatment, little systematic research has been carried out to investigate such a possibility. Future research might profitably address this issue and also specifically examine the effects of low dosage cisplatin-based therapy and the effects of recently developed neuroprotective agents. Finally, there is some evidence to suggest that women may be more susceptible to neurotoxicity during cisplatin therapy, but no gender-related cognitive effects are reported in the cisplatin literature. Future research could usefully investigate gender differences in association with cisplatin chemotherapy.

Motor performance of children during treatment for acute lymphoblastic leukemia

BACKGROUND

Daily life motor skills of children with acute lymphoblastic leukemia (ALL) were studied during treatment using the Movement Assessment Battery for Children (Movement ABC). In addition, the possible relation with vincristine treatment was investigated.

PROCEDURE

Seventeen children treated for ALL, aged 4-12 years, were compared to an age- and sex-matched control group.

RESULTS

The leukemia group performed more poorly than the control group on both fine and gross motor skills. In looking at the number of children with ALL who scored in the clinical range of the different subtests, problems in balance skills were found to be most pronounced at the end of induction therapy. Remarkably, half a year after reinduction therapy, problems with balance had decreased, whereas the number of children with fine motor problems had increased.

CONCLUSIONS

A relation between the gross motor problems and vincristine neurotoxicity seems plausible based on a descriptive analysis of the data, but this was not supported statistically.

Fine motor and handwriting problems after treatment for childhood acute lymphoblastic leukemia

Motor skills were investigated in 18 children 2 years after treatment for acute lymphoblastic leukemia (ALL). Gross and fine motor functioning were examined with the Movement Assessment Battery for Children. Handwriting as a specific fine motor skill was studied with a computerized writing task. We conclude that 2 years after cessation of treatment motor problems in ALL survivors were still present. Dysfunctions were mainly pronounced in handwriting and fine motor skills.

Reproductive effects of chronic administration of murine interferon-gamma

Daily subcutaneous doses of 0.02, 0.2, or 2 mg/kg/d of recombinant murine interferon-gamma (rmuIFN-gamma) were given to mice on postnatal days 8 through 60 to determine effects on maturation, behavioral/ functional development, and reproductive capacity. Male mice receiving 2 mg/kg/d rmuIFN-gamma had delayed sexual maturation, reduced epididymal and testes weights, reduced sperm count and concentration, and sperm abnormalities (crimped flagellum). Mating performance and fertility were also reduced in the absence of altered histopathology of the testes. Males given 0.2 and 2 mg/kg/d had swelling and ulcerative dermatitis around the urogenital area, which were observed after sexual contact and attributed to a bacterial infection. Motor activity (time spent in movement) was decreased in all mice receiving 2 mg/kg/d. No microscopic changes observed in any organs were attributed to rmuIFN-gamma administration.

Delayed, transient encephalopathy after marrow transplantation: case reports and MRI findings in four patients

Subacute encephalopathy developed in four patients within one to two months after undergoing high-dose chemotherapy and bone marrow transplantation or peripheral blood progenitor (stem) cell transplantation for breast cancer, acute myeloid leukemia, and non-Hodgkin's lymphoma. None of the patients had previously known neurologic disorders, central nervous tumor or infection. Two patients presented with generalized tonic, clonic seizures, and two with confusion and lethargy. In all patients lumbar puncture and CT scans of the brain were normal, while magnetic resonance imaging (MRI) demonstrated multifocal predominantly white matter lesions. Phenytoin therapy was given to the two patients with seizures and all four patients improved without specific therapeutic intervention. Repeat MRIs became normal within three months. We report a delayed and transient encephalopathy which appears to be a unique complication of high-dose cytotoxic chemotherapy. The corresponding brain lesions may not be appreciated on CT scans, suggesting an expanded role for MRI studies in patients who develop neurologic findings while undergoing high-dose cytotoxic therapy.