Radiomimetic Cell Cycle Delay Induced by Tetranodecanoyl Phorbol Acetate is Enhanced by Caffeine and by the Protein Kinase Inhibitor 2-aminopurine

The tumour promoter and protein kinase C agonist, 12-O-tetranodecanoyl-phorbol-13-acetate (TPA), has been reported to show a radiomimetic action because it transiently delays the passage of HeLa cells through the G2 phase, as do ionizing radiation and other DNA damaging agents. Caffeine is known to override the G2 delay imposed by DNA damage; it is shown here that caffeine does not override the radiomimetic delay imposed by TPA in HeLa, but instead enhances it, without affecting G2 progression in control cells. Most of the other agents which more specifically affect some of the diverse range of caffeine targets either do not affect G2 progression after TPA, or delay G2 progression in control cells and exert a further delay in the presence of TPA. The exception is 2-aminopurine, a protein kinase inhibitor which has been shown to have an action similar to that of caffeine is allowing progression of the cell cycle to mitosis after the inhibition of DNA synthesis, without affecting normal cycle progression through G2. This agent, like caffeine, also has the contrary action of retarding cycle progression after TPA. It is concluded that the G2 delays induced by ionizing radiation and by TPA operate by different mechanisms, which are modulated in opposite senses by mechanisms involving protein kinase inhibition.

VTE prophylaxis across the continuum of care in U.S. cancer patients

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Background: The period of VTE risk in cancer patients extends beyond the hospital stay. This analysis evaluated VTE prophylaxis patterns for US cancer patients across the continuum of care. Methods: Premier's Perspective inpatient data were cross-matched with Ingenix LabRx outpatient data from the I3 database (January 2005-December 2007) to assess VTE prophylaxis patterns in medical cancer patients at risk of VTE (according to the American College of Chest Physicians 2004 guidelines) and with no contraindications for anticoagulation. Inpatient anticoagulant groups were assigned based on the drug the patient received during hospital stay and were followed by their outpatient prophylaxis use. Patients were evaluated on drug utilization, diagnoses and clinical practice patterns during and after hospitalization. Results: Overall, 75.3% of 2,337 cancer patients did not receive anticoagulation during their hospital stay. Of the 577 patients receiving prophylaxis, 66% received UFH and 25% received enoxaparin ( Table ). The mean length of hospital stay was 3 days after which 97.9% of patients did not receive any prophylaxis within the following 30 days. Of the 50 patients who received outpatient prophylaxis, 60% received warfarin alone and 22% received both enoxaparin and warfarin. Conclusions: This unique analysis presents VTE prophylaxis patterns across the continuum of care. Most cancer patients did not receive anticoagulation in the inpatient or outpatient settings. Further efforts are needed to identify optimal VTE prevention in cancer patients, namely the duration of prophylaxis and how healthcare providers can increase awareness. Financial and editorial support was provided by sanofi-aventis US, Inc.

[Table: see text]

[Table: see text]

Defining hybrid poplar (Populus deltoides x Populus trichocarpa) tolerance to ozone: identifying key parameters

This study examined whether two genotypes of hybrid poplar (Populus deltoides x Populus trichocarpa), previously classified as ozone tolerant and ozone sensitive, had differing physiological and biochemical responses when fumigated with 120 nL L(-1) ozone for 6 h per day for eight consecutive days. Isoprene emission rate, ozone uptake and a number of physiological and biochemical parameters were investigated before, during and after fumigation with ozone. Previous studies have shown that isoprene protects plants against oxidative stress. Therefore, it was hypothesized that these two genotypes would differ in either their basal isoprene emission rates or in the response of isoprene to fumigation by ozone. Our results showed that the basal emission rates of isoprene, physiological responses and ozone uptake rates were all similar. However, significant differences were found in visible damage, carotenoids, hydrogen peroxide (H(2)O(2)), thiobarbituric acid reactions (TBARS) and post-fumigation isoprene emission rates. It is shown that, although the classification of ozone tolerance or sensitivity had been previously clearly and carefully defined using one particular set of parameters, assessment of other key variables does not necessarily lead to the same conclusions. Thus, it may be necessary to reconsider the way in which plants are classified as ozone tolerant or sensitive.

The use of irinotecan, oxaliplatin and raltitrexed for the treatment of advanced colorectal cancer: systematic review and economic evaluation

OBJECTIVES

To evaluate three technologies for the management of advanced colorectal cancer: (1) first-line irinotecan combination [with 5-fluorouracil (5-FU)] or second-line monotherapy; (2) first- or second-line oxaliplatin combination (again, with 5-FU); and (3) raltitrexed, where 5-FU is inappropriate. To examine the role of irinotecan and oxaliplatin in reducing the extent of incurable disease before curative surgery (downstaging).

SOURCES

Ten electronic bibliographic databases covering the period up to August 2004.

METHODS

Searches identified existing studies of the effectiveness and economics of the technologies and any studies that evaluated any of the indications outlined above were included. Data were extracted and assessed generic components of methodological quality. Survival outcomes were meta-analysed.

RESULTS

Seventeen trials were found, of varying methodological quality. Compared with 5-FU, first-line irinotecan improved overall survival (OS) by 2-4 months (p=0.0007), progression-free survival (PFS) by 2-3 months (p<0.00001) and response rates (p<0.001). It offered a different toxicity profile and no quality of life (QoL) advantage. However, second-line irinotecan compared with 5-FU improved OS by 2 months (p=0.035) and PFS by 1 month (p=0.03), and provided a better partial response rate, but with more toxicities and no QoL advantage. Compared with second-line best supportive care, irinotecan improved OS by 2 months (p=0.0001), had a different toxicity profile and maintained baseline QoL longer, but with no overall difference. The addition of oxaliplatin to second-line 5-FU is associated with a borderline significant improvement in overall survival (p<0.07); a significantly higher response rate (<0.0001); and more serious toxicities. There is no evidence for a significant difference in QoL. Schedules with treatment breaks may not reduce clinical effectiveness but reduce toxicity. The addition of oxaliplatin to second-line 5-FU also saw no improvement in OS (p<0.07), better PFS (by 2.1 months, p=0.0001), an 8.9% higher response rate (p<0.0001), more toxicities and no QoL advantage. There was no significant difference in OS or PFS between first-line irinotecan and oxaliplatin combinations except when 5-FU was delivered by bolus injection, when oxaliplatin provided better OS (p=0.032) and response rates (p=0.032), but not PFS (p=0.169). The regimens had different toxicity profiles and neither conferred a QoL advantage. When compared to 5-FU, raltitrexed is associated with no significant difference in overall or progression-free survival; no significant difference in response rates; more vomiting and nausea, but less diarrhoea and mucositis; no significant difference in, or worse QoL. Raltitrexed treatment was cut short in two out of four included trials due to excess toxic deaths. 5-FU followed by irinotecan was inferior to any other sequence. First-line irinotecan/5-FU combination improved OS and PFS, although further unplanned therapy exaggerated the OS effect size. Staged combination therapy (combination oxaliplatin followed by combination irinotecan or vice versa) provided the best OS and PFS, although there was no head-to-head comparison against other treatment plans. In the only trial to use three active chemotherapies in any staged combination, median OS was over 20 months. In another study, the longest median OS from a treatment plan using two active agents was 16.2 months. Where irinotecan or oxaliplatin were used with 5-FU to downstage people with unresectable liver metastases, studies consistently showed response rates of around 50%. Resection rates ranged from 9 to 35% with irinotecan and from 7 to 51% with oxaliplatin. In the one study that compared the regimens, oxaliplatin enabled more resections (p=0.02). Five-year OS rates of 5-26% and disease-free survival rates of 3-11% were reported in studies using oxaliplatin. Alone or in combination, 5-FU was more effective and less toxic when delivered by continuous infusion. Existing economic models were weak because of the use of unplanned second-line therapies in their trial data: the survival benefits in patients on such trials cannot be uniquely attributed to the allocated therapy. Consequently, the economic analyses are either limited to the use of PES (at best, a surrogate outcome) or are subject to confounding. Weaknesses in cost components, the absence of direct in-trial utility estimates and the limited use of sensitivity analysis were identified. Improvements to the methodologies used in existing economic studies are presented. Using data from two trials that planned treatment sequences, an independent economic evaluation of six plans compared with first-line 5-FU followed on progression by second-line irinotecan monotherapy (NHS standard treatment) is presented. 5-FU followed on progression by irinotecan combination cost 13,174 pounds per life-year gained (LYG) and 10,338 pounds per quality-adjusted life-year (QALY) gained. Irinotecan combination followed on progression by additional second-line therapies was estimated to cost 12,418 pounds per LYG and 13,630 pounds per QALY gained. 5-FU followed on progression by oxaliplatin combination was estimated to cost 23,786 pounds per LYG and 31,556 pounds per QALY gained. Oxaliplatin combination followed on progression by additional second-line therapies was estimated to cost 43,531 pounds per LYG and 67,662 pounds per QALY gained. Evaluations presented in this paragraph should be interpreted with caution owing to missing information on the costs of salvage therapies in the trial from which data were drawn. Irinotecan combination followed on progression by oxaliplatin combination cost 12,761 pounds per LYG and 16,663 pounds per QALY gained. Oxaliplatin combination followed on progression by irinotecan combination cost 16,776 pounds per LYG and 21,845 pounds per QALY gained. The evaluation suggests that these two sequences have a cost-effectiveness profile that is favourable in comparison to other therapies currently funded by the NHS. However, the differences in OS observed between the two trials from which data were taken may be a result of heterogeneous patient populations, unbalanced protocol-driven intensity biases or other differences between underlying health service delivery systems.

CONCLUSIONS

Treatment with three active therapies appears most clinically effective and cost-effective. NHS routine data could be used to validate downstaging findings and a meta-analysis using individual patient-level data is suggested to validate the optimal treatment sequence.

Exploring the role and perspectives of mental health nurse practitioners following psychosocial interventions training

Psychosocial interventions (PSI) offer a range of problem-centred activities designed to improve the health and quality of life of clients and their carers. The paper reports the findings of a study on the roles and perspectives of mental health nurse practitioners towards clients with enduring mental illness and their carers following completion of PSI training. Focus groups interviews were conducted with PSI mental health nurse practitioners (n = 8) and data were analysed for thematic content. The results of the study indicated that PSI practitioners developed positive attitudes towards their client following PSI training and this attitudinal change enabled clients to develop more confidence and autonomy in managing the symptoms of their illness in a more empowered way. Focus group participants observed reduced levels of anxiety among clients and their carers. This was attributed to the 'sense of hope' within the caring milieu which was established as a result of collaborative working with the client and family. The findings suggest that there is a need for further exploration of the PSI practitioner role with a particular focus on the centrality of positive attitudes on the development of the therapeutic milieu for clients with severe and enduring mental ill health.

A systematic review and economic evaluation of statins for the prevention of coronary events

OBJECTIVES

To evaluate the clinical effectiveness and cost-effectiveness of statins for the primary and secondary prevention of cardiovascular events in adults with, or at risk of, coronary heart disease (CHD).

DATA SOURCES

Electronic databases were searched between November 2003 and April 2004.

REVIEW METHODS

A review was undertaken to identify and evaluate all literature relating to the clinical and cost effectiveness of statins in the primary and secondary prevention of CHD and cardiovascular disease (CVD) in the UK. A Markov model was developed to explore the costs and health outcomes associated with a lifetime of statin treatment using a UK NHS perspective.

RESULTS

Thirty-one randomised studies were identified that compared a statin with placebo or with another statin, and reported clinical outcomes. Meta-analysis of the available data from the placebo-controlled studies indicates that, in patients with, or at risk of, CVD, statin therapy is associated with a reduced relative risk of all cause mortality, cardiovascular mortality, CHD mortality and fatal myocardial infarction (MI), but not of fatal stroke. It is also associated with a reduced relative risk of morbidity [non-fatal stroke, non-fatal MI, transient ischaemic attack (TIA), unstable angina] and of coronary revascularisation. It is hardly possible, on the evidence available from the placebo-controlled trials, to differentiate between the clinical efficacy of atorvastatin, fluvastatin, pravastatin and simvastatin. However, there is some evidence from direct comparisons between statins to suggest that atorvastatin may be more effective than pravastatin in patients with symptomatic CHD. There is limited evidence for the effectiveness of statins in different subgroups. Statins are generally considered to be well tolerated and to have a good safety profile. This view is generally supported both by the evidence of the trials included in this review and by postmarketing surveillance data. Increases in creatine kinase and myopathy have been reported, but rhabdomyolysis and hepatotoxicity are rare. However, some patients may receive lipid-lowering therapy for as long as 50 years, and long-term safety over such a timespan remains unknown. In secondary prevention of CHD, the incremental cost-effectiveness ratios (ICERs) increase with age varying between pound 10,000 and pound 17,000 per quality adjusted life year (QALY) for ages 45 and 85 respectively. Sensitivity analyses show these results are robust. In primary prevention of CHD there is substantial variation in ICERs by age and risk. The average ICERs weighted by risk range from pound 20,000 to pound 27,500 for men and from pound 21,000 to pound 57,000 for women. The results are sensitive to the cost of statins, discount rates and the modelling time frame. In the CVD analyses, which take into account the benefits of statins on reductions in stroke and TIA events, the average ICER weighted by risk level remains below pound 20,000 at CHD risk levels down to 0.5%. Limitations of the analyses include the requirement to extrapolate well beyond the timeframe of the trial period, and to extrapolate effectiveness results from higher risk primary prevention populations to the treatment of populations at much lower risk. Consequently, the results for the lower age bands and lower risks are subject to greater uncertainty and need to be treated with caution.

CONCLUSIONS

There is evidence to suggest that statin therapy is associated with a statistically significant reduction in the risk of primary and secondary cardiovascular events. As the confidence intervals for each outcome in each prevention category overlap, it is not possible to differentiate, in terms of relative risk, between the effectiveness of statins in primary and secondary prevention. However, the absolute risk of CHD death/non-fatal MI is higher, and the number needed to treat to avoid such an event is consequently lower, in secondary than in primary prevention. The generalisability of these results is limited by the exclusion, in some studies, of patients who were hypersensitive to, intolerant of, or known to be unresponsive to, statins, or who were not adequately compliant with study medication during a placebo run-in phase. Consequently, the treatment effect may be reduced when statins are used in an unselected population. The results of the economic modelling show that statin therapy in secondary prevention is likely to be considered cost-effective. In primary prevention, the cost-effectiveness ratios are dependent on the level of CHD risk and age, but the results for the CVD analyses offer support for the more aggressive treatment recommendation issued by recent guidelines in UK. Evidence on clinical endpoints for rosuvastatin is awaited from on-going trials. The potential targeting of statins at low-risk populations is however associated with major uncertainties, particularly the likely uptake and long-term compliance to lifelong medication by asymptomatic younger patients. The targeting, assessment and monitoring of low-risk patients in primary care would be a major resource implication for the NHS. These areas require further research.

Distribution of radioactivity and metabolite profiling in tumour and plasma following intravenous administration of a colchicine derivative (14C-ZD6126) to tumour-bearing mice

The main aim of the study was to investigate the distribution of radioactivity in the tissues and tumours using quantitative whole-body autoradiography (QWBA), together with a more detailed investigation of plasma and tumour samples, following administration of a single intravenous dose at 200 mg kg(-1) of 14C-ZD6126 to mice bearing subcutaneous Hras5 tumour xenografts. The study also included an assessment of tumour necrosis following administration of a single intravenous dose of non-labelled ZD6126 at 200 mgkg(-1). QWBA analysis showed that drug-related material was widely distributed to the tissues and tumour. In the majority of tissues, concentrations of radioactivity were highest at 15 min and declined rapidly thereafter. The tumour-to-plasma ratio was 0.6:1 at 0.25 h and increased to 6:1 at 48 h, indicating that drug-related material persisted in the tumour longer than in plasma. ZD6126, a phosphate ester, is rapidly hydrolysed to ZD6126 phenol, the active metabolite. The major metabolite in plasma (36% of the sample radioactivity) and all tumour samples (58-83% of the sample radioactivity) was confirmed as ZD6126 phenol. Extensive tumour necrosis was noted by 24h, which was still evident at 48 h, although there was some evidence of tumour regrowth.

Role of EGFR but not HER2 or HER3 gene copy number in predicting sensitivity of head and neck squamous cell carcinoma (SCCHN) cell lines to EGFR tyrosine kinase inhibitors

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Background: EGFR gene copy number has previously been reported to predict for improved overall survival in NSCLC patients treated with gefitinib (IRESSA) or erlotinib compared with placebo [JCO 2006;24:5034–42 & N Engl J Med 2005;353:133–44]. The utility of EGFR gene copy number as a predictive biomarker in other tumour types such as squamous cell carcinoma of the head and neck (SCCHN) is currently under clinical investigation. The present study examined a panel of 20 SCCHN cell lines to identify potential biomarkers predicting in vitro sensitivity to EGFR tyrosine kinase inhibitors (TKIs). Methods: A panel of 20 SCCHN cell lines was screened for sensitivity to gefitinib, vandetanib or erlotinib using a viable cell number endpoint, with G150 values determined for each cell line (inhibitor concentration required to give 50% growth inhibition). Cell lines were blinded and assessed for EGFR, HER2 and HER3 protein expression by ELISA, mutation status by dye-terminator sequencing, and gene copy number by fluorescence in situ hybridisation (FISH). Results: A broad range in sensitivity was observed for all compounds across the panel of 20 SCCHN cell lines (G150 ranging from 0.001uM to =10uM). 12 cell lines were positive for EGFR genomic gain. Sensitivity (GI50 <1uM) to all EGFR TKIs was seen in 11 lines and resistance (GI50 >8uM) in 5 lines. Of the sensitive cell lines, 9 were positive for EGFR genomic gain compared with only 1 of the resistant lines. Furthermore, EGFR protein expression also had a direct association with EGFR TKI sensitivity. In contrast, only 4 cell lines were positive for HER2 or HER3 genomic gain and there was no correlation with sensitivity. The most sensitive cell line was positive for EGFR genomic gain and was the only line to have an EGFR TK mutation (S768I in exon 20). Conclusions: EGFR gene copy number and protein expression appeared to have predictive value in identifying SCCHN cell lines sensitive to EGFR TKIs.

No significant financial relationships to disclose.

Vaginal vault smears after hysterectomy for reasons other than malignancy: a systematic review of the literature

BACKGROUND

Vaginal vault smears are used to detect persisting neoplasia of the lower genital tract after hysterectomy. Recent data suggest both widespread use and uncertain evidence of their effectiveness.

OBJECTIVES

To identify and synthesise evidence on the use and effectiveness of vaginal vault smears and to assess the quality. SEARCH STRATEGY 'vault smear' OR 'vaginal vault smear' OR 'cervical vault smear' OR ('Hysterectomy') AND ('Follow up' OR 'Smear'). SELECTION CRITERIA Primary research, women who had a hysterectomy and were followed up by vault cytology.

DATA COLLECTION AND ANALYSIS

Systematic search (eight electronic databases), supplemented by contact with experts and review of bibliographies. Two independent reviewers determined eligibility/validity and extracted data concerning test performance characteristics. Quality was assessed according to the established criteria.

RESULTS

Of 441 unique references, only 19 were suitable. Quality of studies varied considerably and few were of 'high' methodological quality. Studies were geographically diverse, and were published over more than 40 years in 16 journals. From the higher scoring papers, there were 11 659 hysterectomies [6546, benign; 76, cervical intraepithelial neoplasia (CIN) I/CIN II; 5037, CIN III]. Proportions of abnormal vault smears and abnormal biopsies during follow up increased with worsening histology at hysterectomy (P < 0.0001 and P = 0.0001). There was only one report of vaginal cancer subsequent to hysterectomy for CIN and insufficient data to allow for reliable meta-analysis.

CONCLUSIONS

Vault smears cause anxiety, consume resources and their value is largely unproven. Inconsistency of study design and limited methodological quality means that the value of vault smears could not be established. High-quality research is required to ensure that the guidelines are evidence based.

Measurement of the clinical and cost-effectiveness of non-invasive diagnostic testing strategies for deep vein thrombosis

OBJECTIVES

To estimate the diagnostic accuracy of non-invasive tests for proximal deep vein thrombosis (DVT) and isolated calf DVT, in patients with clinically suspected DVT or high-risk asymptomatic patients, and identify factors associated with variation in diagnostic performance. Also to identify practical diagnostic algorithms for DVT, and estimate the diagnostic accuracy, clinical effectiveness and cost-effectiveness of each.

DATA SOURCES

Electronic databases (to April 2004). A postal survey of hospitals in the UK.

REVIEW METHODS

Selected studies were assessed against validated criteria. A postal survey of hospitals in the UK was undertaken to describe current practice and availability of tests, and identify additional diagnostic algorithms. Pooled estimates of sensitivity, specificity and likelihood ratios were obtained for each test using random effects meta-analysis. The effect of study-level covariates was explored using random effects metaregression. A decision-analytic model was used to combine estimates from the meta-analysis and estimate the diagnostic performance of each algorithm in a theoretical population of outpatients with suspected DVT. The net benefit of using each algorithm was estimated from a health service perspective, using cost--utility analysis, assuming thresholds of willingness to pay of pound 20,000 and pound 30,000 per quality-adjusted life-year (QALY). The model was analysed probabilistically and cost-effectiveness acceptability curves were generated to reflect uncertainty in estimated cost-effectiveness.

RESULTS

Individual clinical features are of limited diagnostic value, with most likelihood ratios being close to 1. Wells clinical probability score stratifies proximal, but not distal, DVT into high-, intermediate- and low-risk categories. Unstructured clinical assessment by experienced clinicians may have similar performance to Wells score. In patients with clinically suspected DVT, D-dimer has 91% sensitivity and 55% specificity for DVT, although performance varies substantially between assays and populations. D-dimer specificity is dependent on pretest clinical probability, being higher in patients with a low clinical probability of DVT. Plethysmography and rheography techniques have modest sensitivity for proximal DVT, poor sensitivity for distal DVT, and modest specificity. Ultrasound has 94% sensitivity for proximal DVT, 64% sensitivity for distal DVT and 94% specificity. Computed tomography scanning has 95% sensitivity for all DVT (proximal and distal combined) and 97% specificity. Magnetic resonance imaging has 92% sensitivity for all DVT and 95% specificity. The diagnostic performance of all tests is worse in asymptomatic patients. The most cost-effective algorithm discharged patients with a low Wells score and negative D-dimer without further testing, and then used plethysmography alongside ultrasound, with venography in selected cases, to diagnose the remaining patients. However, the cost-effectiveness of this algorithm was dependent on assumptions of test independence being met and the ability to provide plethysmography at relatively low cost. Availability of plethysmography and venography is currently limited at most UK hospitals, so implementation would involve considerable reorganisation of services. Two algorithms were identified that offered high net benefit and would be feasible in most hospitals without substantial reorganisation of services. Both involved using a combination of Wells score, D-dimer and above-knee ultrasound. For thresholds of willingness to pay of pound 10,000 or pound 20,000 per QALY the optimal strategy involved discharging patients with a low or intermediate Wells score and negative D-dimer, ultrasound for those with a high score or positive D-dimer, and repeat scanning for those with positive D-dimer and a high Wells score, but negative initial scan. For thresholds of pound 30,000 or more a similar strategy, but involving repeat ultrasound for all those with a negative initial scan, was optimal.

CONCLUSIONS

Diagnostic algorithms based on a combination of Wells score, D-dimer and ultrasound (with repeat if negative) are feasible at most UK hospitals and are among the most cost-effective. Use of repeat scanning depends on the threshold for willingness to pay for health gain. Further diagnostic testing for patients with a low Wells score and negative D-dimer is unlikely to represent a cost-effective use of resources. Recommendations for research include the evaluation of the costs and outcomes of using the optimal diagnostic algorithms in routine practice, the development and evaluation of algorithms appropriate for specific groups of patients with suspected DVT, such as intravenous drug abusers, pregnant patients and those with previous DVT, the evaluation of the role of plethysmography: interaction with other diagnostic tests, outcome of low-risk patients with negative plethysmography and measurement of the costs of providing plethysmography, and methodological research into the incorporation of meta-analytic data into decision-analytic modelling.

Range of self-tests available to buy in the United Kingdom: an Internet survey

We aimed to describe the availability in the United Kingdom of self-tests that are used to diagnose or screen for conditions without involving a health professional. A systematic Internet search identified 104 unique self-tests related to 24 named conditions including cancers, chronic conditions and infections. These self-tests require various samples including blood obtained using a lancet. The samples are processed at home with results available in minutes or sent to a laboratory for processing with results returned to the individual by e-mail or post. Prices per self-test and condition range from < Pounds 1 to Pounds 76. Self-tests are readily available, and further work is needed to assess their impact.

Fatal toxic leukoencephalopathy: clinical, radiological, and necropsy findings in two patients

BACKGROUND

Toxic leukoencephalopathy has been described with inhalation and intravenous consumption of heroin and cocaine. The clinical picture varies widely but the imaging and histological features are characteristic. Magnetic resonance imaging (MRI) typically reveals diffuse bihemispheric white matter lesions. Histologically there is extensive spongiform degeneration of the cerebral white matter.

OBJECTIVE

To report two cases of fatal toxin associated leukoencephalopathy, along with detailed imaging and neuropathological studies.

RESULTS

MRI revealed diffuse white matter changes. Histologically there was widespread confluent vacuolar degeneration of the deep white matter. In both cases, there was sparing of the brain stem and cerebellar white matter. There was evidence of severe and extensive axonal injury.

CONCLUSIONS

This pattern of radiological involvement and histological findings has not previously been reported and may reflect the presence of a yet unidentified impurity.