Voxel-based analysis of T2 hyperintensities in white matter during treatment of childhood leukemia

Progression of brain injuries associated with methotrexate chemotherapy in childhood acute lymphoblastic leukemia

BACKGROUND

Brain bases and progression of methotrexate-associated neurotoxicity and cognitive disturbances remain unknown. We tested whether brain abnormalities worsen in proportion to intrathecal methotrexate(IT-MTX) doses.

METHODS

In this prospective, longitudinal study, we recruited 19 patients with newly diagnosed acute lymphoblastic leukemia 4-to-20 years of age and 20 matched controls. We collected MRI and neuropsychological assessments at a pre-methotrexate baseline and at week 9, week 22, and year 1 during treatment.

RESULTS

Patients had baseline abnormalities in cortical and subcortical gray matter(GM), white matter(WM) volumes and microstructure, regional cerebral blood flow, and neuronal density. Abnormalities of GM, blood flow, and metabolites worsened in direct proportions to IT-MTX doses. WM abnormalities persisted until week 22 but normalized by year 1. Brain injuries were localized to dorsal and ventral attentional and frontoparietal cognitive networks. Patients had cognitive deficits at baseline that persisted at 1-year follow-up.

CONCLUSIONS

Baseline abnormalities are likely a consequence of neuroinflammation and oxidative stress. Baseline abnormalities in WM microstructure and volumes, and blood flow persisted until week 22 but normalized by year 1, likely due to treatment and its effects on reducing inflammation. The cytotoxic effects of IT-MTX, however, likely contributed to continued, progressive cortical thinning and reductions in neuronal density, thereby contributing to enduring cognitive deficits.

IMPACT

Brain abnormalities at a pre-methotrexate baseline likely are due to acute illness. The cytotoxic effects of intrathecal MTX contribute to progressive cortical thinning, reductions in neuronal density, and enduring cognitive deficits. Baseline white matter abnormalities may have normalized via methotrexate treatment and decreasing neuroinflammation. Corticosteroid and leucovorin conferred neuroprotective effects. Our findings suggest that the administration of neuroprotective and anti-inflammatory agents should be considered even earlier than they are currently administered. The neuroprotective effects of leucovorin suggest that strategies may be developed that extend the duration of this intervention or adapt it for use in standard risk patients.

Cortical thinning and altered functional brain coherence in survivors of childhood sarcoma

High-dose chemotherapy is increasingly evidenced to be neurotoxic and result in long-term neurocognitive sequelae. However, research investigating grey matter alterations in childhood cancer patients remains limited. As childhood sarcoma patients receive high-dose chemotherapy, we aimed to investigate cortical brain alterations in adult survivors. We analyzed high-resolution structural (T1-weighted) MRI and resting-state functional MRI (rsfMRI), to derive structural and functional cortical information in survivors of childhood sarcoma, treated with high-dose intravenous chemotherapy (n = 33). These scans were compared to age- and gender- matched controls (n = 34). Cortical volume and thickness were investigated using voxel-based morphometry and vertex-wise surface-based morphometry. Brain regions showing significant group differences in volume or thickness were implemented as seeds of interest to estimate their resting state co-activity with other areas (i.e. functional coherence). We explored whether structural measures were associated with potential risk factors, such as age at diagnosis, and cumulative doses of chemotherapeutic agents (methotrexate, ifosfamide). Finally, we investigated the link between functional regional strength, neurocognitive assessments and daily life complaints. In patients relative to controls we observed lower grey matter volumes in cerebellar and frontal areas, as well as frontal cortical thinning. Cerebellar volume and orbitofrontal thickness appeared dose- and age-related, respectively. Cortical thickness of the parahippocampal area appeared lower, only if the group comparison was not adjusted for depression. This region specifically showed lower functional coherence, which was associated with lower processing speed. This study suggests cortical thinning as well as decreased functional coherence in survivors of childhood sarcoma, which could be important for both long-term attentional functioning and emotional distress in daily life. Frontal areas might be specifically vulnerable during adolescence.

Characterization of Leukoencephalopathy and Association With Later Neurocognitive Performance in Pediatric Acute Lymphoblastic Leukemia

OBJECTIVES

The most common form of pediatric cancer is acute lymphoblastic leukemia (ALL). Magnetic resonance (MR) neuroimaging studies have revealed leukoencephalopathy (LE) in pediatric ALL, but the impact of LE on long-term neurocognitive performance remains unknown. This study aims to objectively characterize the prevalence, extent, and intensity of LE, and their association with later neurocognitive performance.

MATERIALS AND METHODS

Pediatric patients (N = 377) treated for ALL without irradiation underwent MR neuroimaging at 4 time points throughout therapy (end of remission induction [MR1], end of consolidation [MR2], and week 31 [MR3] and week 120 [end therapy, MR4] of continuation treatment) and neurocognitive evaluations at the end of therapy and 2 years later. Generalized estimation equation models with logit link were developed to explore the association between LE prevalence and extent with time points throughout therapy, age at diagnosis (≤5 years or >5 years), treatment risk arm (low risk or standard/high risk), and sex. General linear models were also developed to investigate the association between neuroimaging metrics during treatment and neurocognitive performance at 2-year follow-up.

RESULTS

The prevalence of LE was greatest (22.8%, 74/324) after consolidation therapy. The prevalence of LE increased at MR2 relative to MR1 regardless of treatment risk arm (both P's < 0.001), age group (both P's < 0.001), or sex (male, P < 0.001; female, P = 0.013). The extent of white matter affected also increased at MR2 relative to MR1 regardless of treatment risk arm (standard/high risk, P < 0.001; low risk, P = 0.004), age group (both P's < 0.001), or sex (male, P < 0.001; female, P = 0.001). Quantitative relaxation rates were significantly longer in LE compared with that in normal-appearing white matter in the same examination (T1, P < 0.001; T2, P < 0.001). The LE prevalence early in therapy was associated with increased parent ratings of conduct problems (P = 0.039) and learning difficulties (P = 0.036) at 2-year follow-up compared with that at the end of therapy. A greater extent of LE early in therapy was associated with decreasing performance on a measure of processing speed (P = 0.003) from the end of therapy to 2-year follow-up. A larger extent of LE at the end of therapy was associated with decreased performance in reading (P = 0.004), spelling (P = 0.003), and mathematics (P = 0.019) at 2-year follow-up and increasing problems with attention (omissions, P = 0.045; β, P = 0.015) and memory (list A total recall, P = 0.010) at 2-year follow-up compared with that at the end of therapy.

CONCLUSIONS

In this large cohort of pediatric patients treated for ALL without irradiation, asymptomatic LE during therapy can be seen in almost a quarter of patients, involves as much as 10% of the white matter volume, and is associated with decreasing neurocognitive performance, increasing parent reports of conduct problems, and learning difficulties in survivors.

Cerebrospinal Fluid Biomarkers in Childhood Leukemias

Involvement of the central nervous system (CNS) in childhood leukemias remains a major cause of treatment failures. Analysis of the cerebrospinal fluid constitutes the most important diagnostic pillar in the detection of CNS leukemia and relies primarily on cytological and flow-cytometry studies. With increasing survival rates, it has become clear that treatments for pediatric leukemias pose a toll on the developing brain, as they may cause acute toxicities and persistent neurocognitive deficits. Preclinical research has demonstrated that established and newer therapies can injure and even destroy neuronal and glial cells in the brain. Both passive and active cell death forms can result from DNA damage, oxidative stress, cytokine release, and acceleration of cell aging. In addition, chemotherapy agents may impair neurogenesis as well as the function, formation, and plasticity of synapses. Clinical studies show that neurocognitive toxicity of chemotherapy is greatest in younger children. This raises concerns that, in addition to injury, chemotherapy may also disrupt crucial developmental events resulting in impairment of the formation and efficiency of neuronal networks. This review presents an overview of studies demonstrating that cerebrospinal fluid biomarkers can be utilized in tracing both CNS disease and neurotoxicity of administered treatments in childhood leukemias.

Brain Connectivity and Cognitive Flexibility in Nonirradiated Adult Survivors of Childhood Leukemia

Background

This study aimed to assess functional and structural brain connectivity in adult childhood leukemia survivors and the link with cognitive functioning and previously identified risk factors such as intrathecal methotrexate dose and age at start of therapy.

Methods

Thirty-one nonirradiated adult childhood leukemia survivors and 35 controls underwent cognitive testing and multimodal magnetic resonance imaging (resting state functional MRI, T1-weighted, diffusion-weighted, and myelin water imaging [MWI]). Analyses included dual regression, voxel-based morphometry, advanced diffusion, and MWI modeling techniques besides stepwise discriminant function analysis to identify the most affected executive cognitive domain. Correlations with discrete intrathecal MTX doses and (semi)continuous variables were calculated using Spearman's rank and Pearson's correlation, respectively. All correlation tests were two-sided. Positive and negative T-contrasts in functional and structural MRI analysis were one-sided.

Results

Survivors demonstrated lower functional connectivity between the default mode network (DMN) and inferior temporal gyrus (ITG; P < .008). Additionally, we observed higher fractional anisotropy (FA; P = .04) and lower orientation dispersion index (ODI; P = .008) at the left centrum semiovale, which could-given that several fiber bundles cross this region-suggest selective reduced integrity of the respective white matter tracts. Set shifting reaction time, a measure of cognitive flexibility, was mostly impaired and correlated with lower FA (r = -0.53, P = .003) and higher ODI (r = 0.40, P = .04) in survivors but not with DMN-ITG connectivity. There were no statistically significant differences between survivors and controls in WM or GM volume, nor was there a statistically significant correlation between imaging measurements and age at start of therapy or intrathecal methotrexate dose.

Conclusions

Adult, nonirradiated childhood leukemia survivors show altered brain connectivity, which is linked with cognitive flexibility.

Brain morphology and information processing at the completion of chemotherapy-only treatment for pediatric acute lymphoblastic leukemia

Background: Approximately 50% of survivors of childhood acute lymphoblastic leukemia (ALL) demonstrate cognitive impairments. However, the trajectory of change and contributing neuropathology is unclear, limiting our ability to tailor intervention content and timing. This study aimed to explore information processing abilities and brain morphology early post-treatment for pediatric ALL. Procedure: Twenty-one children at the end of ALL treatment and 18 controls underwent neuropsychological assessment. A subset also completed structural magnetic resonance imaging. Results: A principal component analysis generated two cognitive factors: information processing capacity and information processing speed. Compared to control group, the ALL group displayed deficits in capacity, but not speed. No group differences were identified in morphology. No relationship was identified between capacity or speed and morphology. Conclusion: Early cognitive intervention should target information processing abilities using a system-wide approach. Future studies should employ alternative imaging techniques sensitive to white-matter microstructure when exploring pathology underlying information processing deficits.

Reduced brain microstructural asymmetry in patients with childhood leukemia treated with chemotherapy compared with healthy controls

Microstructural asymmetry of the brain can provide more direct causal explanations of functional lateralization than can macrostructural asymmetry. We performed a cross-sectional diffusion imaging study of 314 patients treated for childhood acute lymphoblastic leukemia (ALL) at a single institution and 92 healthy controls. An asymmetry index based on diffusion metrics was computed to quantify brain microstructural asymmetry. The effects of age and the asymmetry metrics of the two cohorts were examined with t-tests and linear models. We discovered two new types of microstructural asymmetry. Myelin-related asymmetry in controls was prominent in the back brain (89% right), whereas axon-related asymmetry occurred in the front brain (67% left) and back brain (88% right). These asymmetries indicate that white matter is more mature and more myelinated in the left back brain, potentially explaining the leftward lateralization of language and visual functions. The asymmetries increase throughout childhood and adolescence (P = 0.04) but were significantly less in patients treated for ALL (P<0.01), especially in younger patients. Our results indicate that atypical brain development may appear long before patients treated with chemotherapy become symptomatic.

Magnetic Resonance Fingerprinting to Characterize Childhood and Young Adult Brain Tumors

OBJECT

Magnetic resonance fingerprinting (MRF) allows rapid, simultaneous mapping of T1 and T2 relaxation times and may be an important diagnostic tool to measure tissue characteristics in pediatric brain tumors. We examined children and young adults with primary brain tumors to determine whether MRF can discriminate tumor from normal-appearing white matter and distinguish tumor grade.

METHODS

MRF was performed in 23 patients (14 children and 9 young adults) with brain tumors (19 low-grade glioma, 4 high-grade tumors). T1 and T2 values were recorded in regions of solid tumor (ST), peritumoral white matter (PWM), and contralateral white matter (CWM). Nonparametric tests were used for comparison between groups and regions.

RESULTS

Median scan time for MRF and a sequence for tumor localization was 11 min. MRF-derived T1 and T2 values distinguished ST from CWM (T1: 1,444 ± 254 ms vs. 938 ± 96 ms, p = 0.0002; T2: 61 ± 22 ms vs. 38 ± 9 ms, p = 0.0003) and separated high-grade tumors from low-grade tumors (T1: 1,863 ± 70 ms vs. 1,355 ± 187 ms, p = 0.007; T2: 90 ± 13 ms vs. 56 ± 19 ms, p = 0.013). PWM was distinct from CWM (T1: 1,261 ± 359 ms vs. 933 ± 104 ms, p = 0.0008; T2: 65 ± 51 ms vs. 38 ± 8 ms, p = 0.008), as well as from tumor (T1: 1,261 ± 371 ms vs. 1,462 ± 248 ms, p = 0.047).

CONCLUSIONS

MRF is a fast sequence that can rapidly distinguish important tissue components in pediatric brain tumor patients. MRF-derived T1 and T2 distinguished tumor from normal-appearing white matter, differentiated tumor grade, and found abnormalities in peritumoral regions. MRF may be useful for rapid quantitative measurement of tissue characteristics and distinguish tumor grade in children and young adults with brain tumors.

Chemotherapy and the pediatric brain

Survival rates of children with cancer are steadily increasing. This urges our attention to neurocognitive and psychiatric outcomes, as these can markedly influence the quality of life of these children. Neurobehavioral morbidity in childhood cancer survivors affects diverse aspects of cognitive function, which can include attention, memory, processing speed, intellect, academic achievement, and emotional health. Reasons for neurobehavioral morbidity are multiple with one major contributor being chemotherapy-induced central nervous system (CNS) toxicity. Clinical studies investigating the effects of chemotherapy on the CNS in children with cancer have reported causative associations with the development of leukoencephalopathies as well as smaller regional grey and white matter volumes, which have been found to correlate with neurocognitive deficits.Preclinical work has provided compelling evidence that chemotherapy drugs are potent neuro- and gliotoxins in vitro and in vivo and can cause brain injury via excitotoxic and apoptotic mechanisms. Furthermore, chemotherapy triggers DNA (deoxyribonucleic acid) damage directly or through increased oxidative stress. It can shorten telomeres and accelerate cell aging, cause cytokine deregulation, inhibit hippocampal neurogenesis, and reduce brain vascularization and blood flow. These mechanisms, when allowed to operate on the developing brain of a child, have high potential to not only cause brain injury, but also alter crucial developmental events, such as myelination, synaptogenesis, neurogenesis, cortical thinning, and formation of neuronal networks.This short review summarizes key publications describing neurotoxicity of chemotherapy in pediatric cancers and potential underlying pathomechanisms.

Neurodevelopmental consequences of pediatric cancer and its treatment: applying an early adversity framework to understanding cognitive, behavioral, and emotional outcomes

Today, children are surviving pediatric cancer at unprecedented rates, making it one of modern medicine's true success stories. However, we are increasingly becoming aware of several deleterious effects of cancer and the subsequent "cure" that extend beyond physical sequelae. Indeed, survivors of childhood cancer commonly report cognitive, emotional, and psychological difficulties, including attentional difficulties, anxiety, and posttraumatic stress symptoms (PTSS). Cognitive late- and long-term effects have been largely attributed to neurotoxic effects of cancer treatments (e.g., chemotherapy, cranial irradiation, surgery) on brain development. The role of childhood adversity in pediatric cancer - namely, the presence of a life-threatening disease and endurance of invasive medical procedures - has been largely ignored in the existing neuroscientific literature, despite compelling research by our group and others showing that exposure to more commonly studied adverse childhood experiences (i.e., domestic and community violence, physical, sexual, and emotional abuse) strongly imprints on neural development. While these adverse childhood experiences are different in many ways from the experience of childhood cancer (e.g., context, nature, source), they do share a common element of exposure to threat (i.e., threat to life or physical integrity). Therefore, we argue that the double hit of early threat and cancer treatments likely alters neural development, and ultimately, cognitive, behavioral, and emotional outcomes. In this paper, we (1) review the existing neuroimaging research on child, adolescent, and adult survivors of childhood cancer, (2) summarize gaps in our current understanding, (3) propose a novel neurobiological framework that characterizes childhood cancer as a type of childhood adversity, particularly a form of early threat, focusing on development of the hippocampus and the salience and emotion network (SEN), and (4) outline future directions for research.

Brain structure, working memory and response inhibition in childhood leukemia survivors

INTRODUCTION

Survival rates for children with acute lymphoblastic leukemia (ALL) approach 95%. At the same time, there is growing concern that chemotherapy causes alterations in brain development and cognitive abilities. We performed MRI measurements of white and gray matter volume to explore how variation in brain structure may be related to cognitive abilities in ALL survivors and healthy controls.

METHODS

The sample included 24 male ALL survivors who had completed contemporary treatment 3-11 years prior, and 21 age- and sex-matched controls. Participants were between 8 and 18 years old. Working memory and motor response inhibition were measured with the N-Back and Stop Signal Tasks (SST), respectively. Participants underwent 3T structural MRI to assess white and gray matter volumes overall, lobe-wise, and in cortical and atlas-identified subcortical structures. Mental health was assessed with the Child Behavioral Checklist.

RESULTS

ALL survivors performed more poorly on measures of working memory and response inhibition than controls. Frontal and parietal white matter, temporal and occipital gray matter volume, and volumes of subcortical white and gray matter structures were significantly reduced in ALL survivors compared with controls. Significant structure-function correlations were observed between working memory performance and volume of the amygdala, thalamus, striatum, and corpus callosum. Response inhibition was correlated with frontal white matter volume. No differences were found in psychopathology.

CONCLUSIONS

Compared with controls, a reduction in volume across brain regions and tissue types, was detectable in ALL survivors years after completion of therapy. These structural alterations were correlated with neurocognitive performance, particularly in working memory. Confirming these observations in a larger, more representative sample of the population is necessary. Additionally, establishing the time course of these changes-and the treatment, genetic, and environmental factors that influence them-may provide opportunities to identify at-risk patients, inform the design of treatment modifications, and minimize adverse cognitive outcomes.

Chemotherapy Pharmacodynamics and Neuroimaging and Neurocognitive Outcomes in Long-Term Survivors of Childhood Acute Lymphoblastic Leukemia

PURPOSE

To examine associations among methotrexate pharmacodynamics, neuroimaging, and neurocognitive outcomes in long-term survivors of childhood acute lymphoblastic leukemia treated on a contemporary chemotherapy-only protocol.

PATIENTS AND METHODS

This longitudinal study linked pharmacokinetic assays collected during therapy to neurocognitive and brain imaging outcomes during long-term follow-up. A total of 218 (72.2%) of 302 eligible long-term survivors were recruited for outcome studies when they were more than 5 years post-diagnosis and older than 8 years of age. At long-term follow-up, survivors were an average of 13.8 years old and 7.7 years from diagnosis, and 51% were male. Neurocognitive testing, functional magnetic resonance imaging (MRI) during an executive function task, and structural MRI with diffusion tensor imaging were conducted. Generalized linear models were developed to identify predictors, and models were adjusted for age at diagnosis, sex, and parent education.

RESULTS

Intelligence was within normal limits (mean, 98; standard deviation, 14) compared with population expectations (mean, 100; standard deviation, 15), though measures of executive function, processing speed, and memory were less than population means (all P < .02 after correction for false discovery rates). Higher plasma concentration of methotrexate was associated with a poorer executive function score (P < .02). Higher plasma methotrexate was also associated with higher functional MRI activity, with thicker cortices in dorsolateral prefrontal brain regions, and with white matter microstructure in the frontostriatal tact. Neurocognitive impairment was associated with these imaging findings as well. Associations did not change after adjustment for age or dose of leucovorin rescue.

CONCLUSION

Survivors of childhood acute lymphoblastic leukemia treated on contemporary chemotherapy-only protocols demonstrate executive dysfunction. A higher plasma concentration of methotrexate was associated with executive dysfunction as well as with a thicker cortex and higher activity in frontal brain regions, regions often associated with executive function.

MR Imaging Evaluation of Intracerebral Hemorrhages and T2 Hyperintense White Matter Lesions Appearing after Radiation Therapy in Adult Patients with Primary Brain Tumors

The purpose of our study was to determine the frequency and severity of intracerebral hemorrhages and T2 hyperintense white matter lesions (WMLs) following radiation therapy for brain tumors in adult patients. Of 648 adult brain tumor patients who received radiation therapy at our institute, magnetic resonance (MR) image data consisting of a gradient echo (GRE) and FLAIR T2-weighted image were available three and five years after radiation therapy in 81 patients. Intracerebral hemorrhage was defined as a hypointense dot lesion appearing on GRE images after radiation therapy. The number and size of the lesions were evaluated. The T2 hyperintense WMLs observed on the FLAIR sequences were graded according to the extent of the lesion. Intracerebral hemorrhage was detected in 21 (25.9%) and 35 (43.2) patients in the three- and five-year follow-up images, respectively. The number of intracerebral hemorrhages per patient tended to increase as the follow-up period increased, whereas the size of the intracerebral hemorrhages exhibited little variation over the course of follow-up. T2 hyperintense WMLs were observed in 27 (33.3%) and 32 (39.5) patients in the three and five year follow-up images, respectively. The age at the time of radiation therapy was significantly higher (p < 0.001) in the patients with T2 hyperintense WMLs than in those without lesions. Intracerebral hemorrhages are not uncommon in adult brain tumor patients undergoing radiation therapy. The incidence and number of intracerebral hemorrhages increased over the course of follow-up. T2 hyperintense WMLs were observed in more than one-third of the study population.

Cortical surface area and thickness in adult survivors of pediatric acute lymphoblastic leukemia

BACKGROUND

Advances in the treatment of acute lymphoblastic leukemia (ALL) have led to great improvements in survival rates and outcomes, but there is concern about cognitive late effects. We aimed to determine whether ALL survivors have smaller cortical surface area and/or thickness, and test whether this is related to disease and treatment variables and self-reported executive functioning in everyday life.

PROCEDURE

Magnetic resonance imaging (MRI) scans from 130 adult long-term survivors of childhood ALL (age: 18-46 years; age at diagnosis: 0-16 years; years since diagnosis: 7-40) and 130 healthy controls were assessed to estimate and compare regional cortical surface area and thickness. Information on disease and treatment factors were obtained from patients' records, and executive functioning in survivors was measured using a validated questionnaire (BRIEF-A).

RESULTS

Smaller cortical surface area was observed in several regions in both cerebral hemispheres in ALL survivors. In these regions, mean surface area was 4.1-5.5% smaller in ALL survivors compared to healthy controls. In contrast, only one region showed lower cortical thickness in ALL survivors. There were no significant associations between cortical surface area/thickness in these regions and disease or treatment variables. In ALL survivors, smaller surface area in prefrontal regions, encompassing parts of the superior frontal gyri and the left anterior cingulate cortex, was associated with problems in executive functioning, specifically with emotional control and self-monitoring.

CONCLUSIONS

ALL survivors had smaller surface area in several cortical regions and smaller surface area in prefrontal regions was associated with reported problems in executive functioning.

Altered resting state functional connectivity in young survivors of acute lymphoblastic leukemia

BACKGROUND

Chemotherapy treatment for pediatric acute lymphoblastic leukemia (ALL) has been associated with long-term cognitive impairments in some patients. However, the neurobiologic mechanisms underlying these impairments, particularly in young survivors, are not well understood. This study aimed to examine intrinsic functional brain connectivity in pediatric ALL and its relationship with cognitive status.

PROCEDURE

We obtained resting state functional magnetic resonance imaging (rsfMRI) and cognitive testing data from 15 ALL survivors age 8-15 years and 14 matched healthy children. The ALL group had a history of intrathecal chemotherapy treatment but were off-therapy for at least 6 months at the time of enrollment. We used seed-based analyses to compare intrinsic functional brain network connectivity between the groups. We also explored correlations between connectivity and cognitive performance, demographic, medical, and treatment variables.

RESULTS

We demonstrated significantly reduced connectivity between bilateral hippocampus, left inferior occipital, left lingual gyrus, bilateral calcarine sulcus, and right amygdala in the ALL group compared to controls. The ALL group also showed regions of functional hyperconnectivity including right lingual gyrus, precuneus, bilateral superior occipital lobe, and right inferior occipital lobe. Functional hypoconnectivity was associated with reduced cognitive function as well as younger age at diagnosis in the ALL group.

CONCLUSIONS

This is the first study to demonstrate that intrinsic functional brain connectivity is disrupted in pediatric ALL following chemotherapy treatment. These results help explain cognitive dysfunction even when objective test performance is seemingly normal. Children diagnosed at a younger age may show increased vulnerability to altered functional brain connectivity.

Impact of chemotherapy for childhood leukemia on brain morphology and function

OBJECTIVE

Using multidisciplinary treatment modalities the majority of children with cancer can be cured but we are increasingly faced with therapy-related toxicities. We studied brain morphology and neurocognitive functions in adolescent and young adult survivors of childhood acute, low and standard risk lymphoblastic leukemia (ALL), which was successfully treated with chemotherapy. We expected that intravenous and intrathecal chemotherapy administered in childhood will affect grey matter structures, including hippocampus and olfactory bulbs, areas where postnatal neurogenesis is ongoing.

METHODS

We examined 27 ALL-survivors and 27 age-matched healthy controls, ages 15-22 years. ALL-survivors developed disease prior to their 11th birthday without central nervous system involvement, were treated with intrathecal and systemic chemotherapy and received no radiation. Volumes of grey, white matter and olfactory bulbs were measured on T1 and T2 magnetic resonance images manually, using FIRST (FMRIB's integrated Registration and Segmentation Tool) and voxel-based morphometry (VBM). Memory, executive functions, attention, intelligence and olfaction were assessed.

RESULTS

Mean volumes of left hippocampus, amygdala, thalamus and nucleus accumbens were smaller in the ALL group. VBM analysis revealed significantly smaller volumes of the left calcarine gyrus, both lingual gyri and the left precuneus. DTI data analysis provided no evidence for white matter pathology. Lower scores in hippocampus-dependent memory were measured in ALL-subjects, while lower figural memory correlated with smaller hippocampal volumes.

INTERPRETATION

Findings demonstrate that childhood ALL, treated with chemotherapy, is associated with smaller grey matter volumes of neocortical and subcortical grey matter and lower hippocampal memory performance in adolescence and adulthood.

Brain volume and cognitive function in adult survivors of childhood acute lymphoblastic leukemia

The survival rate for childhood acute lymphoblastic leukemia (ALL) is greater than 80%. However, many of these survivors develop long-term chronic health conditions, with a relatively common late effect being neurocognitive dysfunction. Although neurocognitive impairments have decreased in frequency and severity as treatment has evolved, there is a subset of survivors in the current treatment era that are especially vulnerable to the neurotoxic effects of ALL and its treatment. Additionally, little is known about long-term brain development as survivors mature into adulthood. A recent study by Zeller et al. compared neurocognitive function and brain volume in 130 adult survivors of childhood ALL to 130 healthy adults matched on age and sex. They identified the caudate as particularly sensitive to the neurotoxic effects of chemotherapy. We discuss the implications and limitations of this study, including how their findings support the concept of individual vulnerability to ALL and its treatment.

Accelerated aging, decreased white matter integrity, and associated neuropsychological dysfunction 25 years after pediatric lymphoid malignancies

PURPOSE

CNS-directed chemotherapy (CT) and cranial radiotherapy (CRT) for childhood acute lymphoblastic leukemia or lymphoma have various neurotoxic properties. This study aimed to assess their impact on the maturing brain 20 to 30 years after diagnosis, providing a much stronger perspective on long-term quality of life than previous studies.

PATIENTS AND METHODS

Ninety-three patients treated between 1978 and 1990 at various intensities, with and without CRT, and 49 healthy controls were assessed with magnetic resonance diffusion tensor imaging (DTI) and neuropsychological tests. Differences in fractional anisotropy (FA)-a DTI measure describing white matter (WM) microstructure-were analyzed by using whole brain voxel-based analysis.

RESULTS

CRT-treated survivors demonstrated significantly decreased FA compared with controls in frontal, parietal, and temporal WM tracts. Trends for lower FA were seen in the CT-treated survivors. Decreases in FA correlated well with neuropsychological dysfunction. In contrast to the CT group and controls, the CRT group showed a steep decline of FA with age at assessment. Younger age at cranial irradiation and higher dosage were associated with worse outcome of WM integrity.

CONCLUSION

CRT-treated survivors show decreased WM integrity reflected by significantly decreased FA and associated neuropsychological dysfunction 25 years after treatment, although effects of CT alone seem mild. Accelerated aging of the brain and increased risk of early onset dementia are suspected after CRT, but not after CT.

Effects of chemotherapy on the brain in childhood: diffusion tensor imaging of subtle white matter damage

INTRODUCTION

With reducing mortality in children with hematological malignancies, the survivors' quality of life regarding development of chronic neurological disturbances is important. We aimed to determine whether chemotherapy affects white matter (WM).

METHODS

Using brain diffusion tensor imaging, we evaluated 17 patients (15 with acute lymphoblastic leukemia, 2 with non-Hodgkin's lymphoma; 9 male, 8 female; age, 1.6-13 years) before and after chemotherapy. We measured the quantitative values of fractional anisotropy (FA) and apparent diffusion coefficient (ADC) at the regions of interest (ROIs) such as periventricular WM, corona radiata, posterior limb of the internal capsule, and corpus callosum. We assessed sensorimotor and callosal tracts by tractography.

RESULTS

Reduction in FA and increase in ADC were significant at the ROIs of the left and right anterior periventricular WM and corona radiata and at the tract passing through the genu. A significant reduction in FA with a nonsignificant increase in ADC was seen at the ROI of the genu and at the tracts passing through the body and isthmus.

CONCLUSION

Chemotherapy in children with hematological malignancies predominantly affects the frontal WM. This finding might indicate a negative effect of chemotherapy on neurological development in children with hematological malignancies.

Translational research: the changing landscape of drug discovery

Drug discovery represents the first step in the creation of new drugs, and takes place in academic institutions, biotech companies, and large pharmaceutical corporations. Until recently, these sectors have each operated independently with little collaboration between those at the forefront of discovery research and those with experience in developing drugs. With the rise of translational research these relationships are shifting and new hubs are emerging, as key players seek to pool the expertise necessary to generate new therapies by linking laboratory discoveries directly to unmet clinical needs. In this article I discuss how the increasing adoption of translational research is leading to novel integrated discovery nexuses that may change the landscape of drug discovery.

Evidence of change in brain activity among childhood cancer survivors participating in a cognitive remediation program

Increased understanding of the underlying mechanisms of cognitive remediation is needed to facilitate development of intervention strategies for childhood cancer survivors experiencing cognitive late effects. Accordingly, a pilot functional magnetic resonance imaging (fMRI) study was conducted with 14 cancer survivors (12.02 ± 0.09 years old), who participated in a cognitive remediation clinical trial, and 28 healthy children (12.7 ± 0.6 years old). The ventral visual areas, cerebellum, supplementary motor area, and left inferior frontal cortex were significantly activated in the healthy participants during a continuous performance task. In survivors, brain activation in these regions was diminished at baseline, and increased upon completion of remediation and at a 6-month follow-up. The fMRI activation index for each region of interest was inversely associated with the Conners' Clinical Competence Index (p<.01). The pilot study suggests that fMRI is useful in evaluating neural responses to cognitive remediation.

GAT: a graph-theoretical analysis toolbox for analyzing between-group differences in large-scale structural and functional brain networks

In recent years, graph theoretical analyses of neuroimaging data have increased our understanding of the organization of large-scale structural and functional brain networks. However, tools for pipeline application of graph theory for analyzing topology of brain networks is still lacking. In this report, we describe the development of a graph-analysis toolbox (GAT) that facilitates analysis and comparison of structural and functional network brain networks. GAT provides a graphical user interface (GUI) that facilitates construction and analysis of brain networks, comparison of regional and global topological properties between networks, analysis of network hub and modules, and analysis of resilience of the networks to random failure and targeted attacks. Area under a curve (AUC) and functional data analyses (FDA), in conjunction with permutation testing, is employed for testing the differences in network topologies; analyses that are less sensitive to the thresholding process. We demonstrated the capabilities of GAT by investigating the differences in the organization of regional gray-matter correlation networks in survivors of acute lymphoblastic leukemia (ALL) and healthy matched Controls (CON). The results revealed an alteration in small-world characteristics of the brain networks in the ALL survivors; an observation that confirm our hypothesis suggesting widespread neurobiological injury in ALL survivors. Along with demonstration of the capabilities of the GAT, this is the first report of altered large-scale structural brain networks in ALL survivors.

Cognitive reserve and brain volumes in pediatric acute lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) is associated with long-term, progressive cognitive deficits and white matter injury. We measured global and regional white and gray matter as well as cognitive function and examined relationships between these variables and cognitive reserve, as indicated by maternal education level, in 28 young survivors of ALL and 31 healthy controls. Results indicated significantly reduced white matter volumes and cognitive testing scores in the ALL group compared to controls. Maternal education was inversely related to both global and regional white matter and directly related to gray matter in ALL and was directly related to both gray and white matter in controls, consistent with the cognitive reserve hypothesis. Cognitive performance was associated with different brain regions in ALL compared to controls. Maternal education was significantly positively correlated with working and verbal memory in ALL as well as processing speed and verbal memory in controls, improving models of cognitive outcome over medical and/or demographic predictors. Our findings suggest that cognitive reserve may be an important factor in brain injury and cognitive outcome in ALL. Additionally, children with ALL may experience some neural reorganization related to cognitive outcome.

Attention and working memory abilities in children treated for acute lymphoblastic leukemia

BACKGROUND

To extend investigation beyond global cognitive measures prevalent in the literature, this study examined attention and working memory (WM) abilities of survivors of childhood acute lymphoblastic leukemia (ALL), the separate contributions of attention and WM to intelligence quotient (IQ), and their association with neuroimaging changes.

METHODS

Ninety-seven children with ALL received risk-directed therapy based on presenting clinical and biological factors. During consolidation therapy, low-risk patients received half the dose of intravenous methotrexate that standard-risk/high-risk patients received, and fewer doses of triple intrathecal therapy. Patients were classified according to end of consolidation magnetic resonance imaging scans (normal or leukoencephalopathy), and continuous measures of white matter structure were computed. As part of the protocol study, children completed cognitive assessment 2 years later (completion of therapy), using Digit Span Forward (DSF) for attention and Digit Span Backward (DSB) for WM.

RESULTS

For the total sample and the standard-/high-risk group, Total Digit Span (TDS), DSF, and DSB were impaired relative to norms (P<.05). In the low-risk group, only DSB was impaired (P<.0001). Across groups, a higher percentage of patients performed below the average range (scale score<7) on DSB (66%) compared with the DSF (14%) or TDS (18%). Regression analysis indicated that DSB predicted estimated IQ (P<.05), after accounting for DSF. Leukoencephalopathy was predictive of lower TDS (P<.05).

CONCLUSIONS

WM appears to be especially sensitive to treatment-related changes in ALL survivors, detecting difficulties potentially missed by global intelligence measures. These findings may facilitate the identification of vulnerable neural pathways and the development of targeted cognitive interventions.