Neurophysiological evaluation of late effects of adjuvant high-dose chemotherapy on cognitive function

Advances of neuroimaging in chemotherapy related cognitive impairment (CRCI) of patients with breast cancer

BACKGROUND

Chemotherapy related cognitive impairment (CRCI) has seriously affected the quality of life (QOL) of patients with breast cancer (BCs), thus the neurobiological mechanism of CRCI attracted widespread attention. Previous studies have found that chemotherapy causes CRCI through affecting brain structure, function, metabolism, and blood perfusion.

FINDINGS

A variety of neuroimaging techniques such as functional magnetic resonance imaging (fMRI), event-related potential (ERP), near-infrared spectroscopy (NIRS) have been widely applied to explore the neurobiological mechanism of CRCI.

CONCLUSION

This review summarized the progress of neuroimaging research in BCs with CRCI, which provides a theoretical basis for further exploration of CRCI mechanism, disease diagnosis and symptom intervention in the future. Multiple neuroimaging techniques for CRCI research.

Cognitive adverse effects of chemotherapy and immunotherapy: are interventions within reach?

One in three people will be diagnosed with cancer during their lifetime. The community of cancer patients is growing, and several common cancers are becoming increasingly chronic; thus, cancer survivorship is an important part of health care. A large body of research indicates that cancer and cancer therapies are associated with cognitive impairment. This research has mainly concentrated on chemotherapy-associated cognitive impairment but, with the arrival of immunotherapies, the focus is expected to widen and the number of studies investigating the potential cognitive effects of these new therapies is rising. Meanwhile, patients with cognitive impairment and their healthcare providers are eagerly awaiting effective approaches to intervene against the cognitive effects of cancer treatment. In this Review, we take stock of the progress that has been made and discuss the steps that need to be taken to accelerate research into the biology underlying cognitive decline following chemotherapy and immunotherapy and to develop restorative and preventive interventions. We also provide recommendations to clinicians on how to best help patients who are currently experiencing cognitive impairment.

Four decades of chemotherapy-induced cognitive dysfunction: comprehensive review of clinical, animal and in vitro studies, and insights of key initiating events

Cognitive dysfunction has been one of the most reported and studied adverse effects of cancer treatment, but, for many years, it was overlooked by the medical community. Nevertheless, the medical and scientific communities have now recognized that the cognitive deficits caused by chemotherapy have a strong impact on the morbidity of cancer treated patients. In fact, chemotherapy-induced cognitive dysfunction or 'chemobrain'  (also named also chemofog) is at present a well-recognized effect of chemotherapy that could affect up to 78% of treated patients. Nonetheless, its underlying neurotoxic mechanism is still not fully elucidated. Therefore, this work aimed to provide a comprehensive review using PubMed as a database to assess the studies published on the field and, therefore, highlight the clinical manifestations of chemobrain and the putative neurotoxicity mechanisms.In the last two decades, a great number of papers was published on the topic, mainly with clinical observations. Chemotherapy-treated patients showed that the cognitive domains most often impaired were verbal memory, psychomotor function, visual memory, visuospatial and verbal learning, memory function and attention. Chemotherapy alters the brain's metabolism, white and grey matter and functional connectivity of brain areas. Several mechanisms have been proposed to cause chemobrain but increase of proinflammatory cytokines with oxidative stress seem more relevant, not excluding the action on neurotransmission and cellular death or impaired hippocampal neurogenesis. The interplay between these mechanisms and susceptible factors makes the clinical management of chemobrain even more difficult. New studies, mainly referring to the underlying mechanisms of chemobrain and protective measures, are important in the future, as it is expected that chemobrain will have more clinical impact in the coming years, since the number of cancer survivors is steadily increasing.

Chemo-brain: An activation likelihood estimation meta-analysis of functional magnetic resonance imaging studies

Adults with non-central nervous system (CNS) cancers frequently report problems in attention, memory and executive function during or after chemotherapy, referred to as cancer-related cognitive dysfunction (CRCD). Despite numerous studies investigating CRCD, there is no consensus regarding the brain areas implicated. We sought to determine if there are brain areas that consistently show either hyper- or hypo-activation in people treated with chemotherapy for non-CNS cancer (Chemo+). Using activation likelihood estimation on brain coordinates from 14 fMRI studies yielding 25 contrasts from 375 Chemo+ and 429 chemotherapy-naive controls while they performed cognitive tasks, the meta-analysis yielded two significant clusters which are part of the frontoparietal attention network, both showing lower activation in Chemo+. One cluster peaked in the left superior parietal cortex, extending into precuneus, inferior parietal lobule, and angular gyrus. The other peaked in the right superior prefrontal areas, extending into inferior prefrontal cortex. We propose that these observed lower activations reflect a dysfunction in mobilizing and/or sustaining attention due to depletion of cognitive resources. This could explain higher level of mental fatigue reported by Chemo+ and why cancer survivors report problems in a wide variety of cognitive domains.

Prospective evaluation of functional brain activity and oxidative damage in breast cancer: changes in task-induced deactivation during a working memory task

Cancer-related cognitive dysfunction is an important issue for breast cancer survivors. Previous research has identified both cross-sectional and longitudinal alterations in brain function related to cancer status and treatment. In this study, we prospectively collected functional magnetic resonance imaging data in breast cancer cases treated with adjuvant chemotherapy and in controls with no cancer history during a working memory task. Data and blood specimens were collected immediately prior to the start of treatment (baseline) and following completion of treatment (follow-up), and at yoked intervals for controls. In secondary analysis we assessed the levels of oxidative DNA damage in peripheral blood lymphocytes of cases and controls using the Comet assay. A significant group*time interaction revealed reduced deactivation in the superior frontal gyrus in the controls at follow-up, in contrast to cases, who exhibited similar magnitude of deactivation at baseline and follow-up. Working memory performance indicated a significant improvement in the controls at follow-up, and no change in performance in cases. In secondary analyses, oxidative DNA damage levels were elevated in the cases at follow-up compared to controls, but no associations were found between the Comet assay variables and functional imaging at either time-point or group. In light of previous reports on task induced deactivations, our findings reflect continuing effortful processing at follow-up in the breast cancer group, with relatively less effortful processing in the control group given the reduced novelty and practice effects from the baseline to follow-up.

Protective effect of nanocurcumin against neurotoxicity induced by doxorubicin in rat's brain

Cognitive impairment is one of the serious side effects that cancer-treated patients suffer from after treatment by doxorubicin (DOX). Investigating the mechanisms underlying this impairment is crucial for its treatment or prevention. The current study investigates the cortical and hippocampal neurochemical changes induced by an acute dose of DOX (20 mg/kg, i.p.) and evaluates the neuroprotective effect of nanocurcumin (NC) (50 mg/kg, p.o.) against these changes. Animals were randomly divided into four groups, control, rats treated with either NC or DOX, and the fourth group treated with NC prior to DOX. Cortical dopamine level has significantly increased (71.88 %) after DOX injection. This was associated with a significant rise in the levels of lipid peroxidation (183.99 %, 201.4 %) and nitric oxide (36.54 %, 55 %) and a significant reduction in reduced glutathione (13 %, 21.44 %) in the cortex and hippocampus, respectively. In addition, DOX inhibited the cortical and hippocampal activities of acetylcholinesterase (94.82 %, 62.75 %) and monoamine oxidase (64.40 %, 68.84 %), respectively. Protection with NC mitigates the changes induced in the oxidative stress parameters by DOX. However, the effect on the activities of AchE and MAO was insignificant. This was reflected in the level of dopamine that showed non-significant changes in comparison to control and DOX-treated rats. The present findings indicate that oxidative stress, inhibition in AchE, MAO, and the subsequent elevation in dopamine could have a crucial role in mediating the chemo-brain adverse effects induced by DOX. In addition, protection with NC mitigated some of these adverse effects thus rendering DOX more tolerable.

Measurement, outcomes and interventions of cognitive function after breast cancer treatment: A narrative review

Cancer-related cognitive impairment (CRCI) is a common complaint in breast cancer patients, especially related to chemotherapy. It is characterized as cognitive disorders in areas of memory, attention and executive function, which can negatively affect patients' quality of life and their ability to work. While various assessment methods of CRCI cause highly diverse results in CRCI-related studies. Currently, it is not clear how cerebral structure and function change in breast cancer patients and underlying mechanisms of developing CRCI are still undefined. Intervention research is limited. This article reviews the results of CRCI-related studies and research progress and discusses the advantages and limits of various methods. Besides, the mechanisms and intervention strategies are reviewed.

Cognitive impairments in breast cancer survivors treated with chemotherapy: a study based on event-related potentials

PURPOSE

Chemotherapy-related cognitive impairments in breast cancer patients were usually reported through cognitive questionnaires or scales which may be subjective and insensitive. This study is to assess the effect of chemotherapy on cognitive function in breast cancer patients stratified by age using objective electrophysiological measure, the P300 component of event-related potentials (ERPs) with a large sample size.

METHODS

Totally, 529 primary breast cancer patients, including 178 cases at initial diagnosis stage and before chemotherapy (Group1), 167 cases during chemotherapy (Group2), and 184 cases post chemotherapy and during follow-up period (Group3), were examined with ERPs (P300 component) to assess the effect of chemotherapy on their cognitive function.

RESULTS

There were significant differences of P300 latency in Group2 (364.74 ± 15.73 ms) and Group3 (364.02 ± 17.12 ms, mean follow-up period of 2.42 years) compared with Group1 (355.13 ± 19.47 ms, P < 0.001), respectively. With further age stratification: in patients of < 50 years, P300 latency was significantly prolonged in Group2 and Group3 compared with Group1 (P < 0.001), respectively; in patients of 50-59 years, P300 latency was significantly prolonged in Group2 compared with Group1 (P < 0.05), but without difference in Group1 and Group3 (P>0.05); In patients of ≥ 60 years, there were no differences of P300 latency among three the groups (P>0.05).

CONCLUSIONS

It is first suggested by our objective detection data that the side effect of chemotherapy on cognitive functions in breast cancer patients may decrease with age. Electrophysiological cognitive impairments mainly occur in younger breast cancer patients undergoing chemotherapy and would last for years after chemotherapy, which highlights the importance of early intervention for those patients, especially in younger patients.

Psychiatric, behavioral, and cognitive disorders in patients with extracranial cancers

Patients with cancer may report neuropsychiatric abnormalities including cognitive impairment, behavioral disturbances, and psychiatric disorders that potentially worsen their quality of life, reduce their treatment response, and aggravate their overall prognosis. Neuropsychiatric disturbances have a different pathophysiology, including immuno-inflammatory and neuroendocrine mechanisms, as a consequence of oncologic treatments (chemo- and radio-therapy). Among clinicians involved in the management of such patients, psychiatrists need to pay particular attention in recognizing behavioral disturbances that arise in oncologic patients, and determining those that may be effectively treated with psychotropic medications, psychotherapeutic interventions, and an integration of them. Through the contribution of different clinicians actively involved in the management of oncological patients, the present review is ultimately aimed at updating psychiatrists in relation to the pathophysiological mechanisms responsible for the onset of cognitive, affective, and behavioral syndromes in these patients, along with epidemiologic and clinical considerations and therapeutic perspectives.

[White matter alterations after chemotherapy and radiation]

Nowadays chemotherapy and radiotherapy are fundamental therapy concepts in the guidelines of malignant tumors of the central nervous system. Both therapy concepts can cause neurological symptoms or white matter alterations can occur, which can be classified into acute, subacute and chronic. Both symptoms and white matter alterations during acute and subacute phases are in most cases completely reversible, whereas chronic white matter alterations can lead to severe neurological limitations and further impair the quality of life of cancer patients.

Do Patients With Advanced Cancer Have the Ability to Make Informed Decisions for Participation in Phase I Clinical Trials?

Purpose Patients with advanced cancer (ACPs) participating in phase I clinical trials inadequately understand many elements of informed consent (IC); however, the prevalence and impact of cognitive impairment has not been described. Patients and Methods ACPs enrolled onto phase I trials underwent neuropsychological assessment to evaluate cognitive functioning (CF) covering the following domains: memory (Hopkins Verbal Learning Test), executive functioning (Trail Making Test B), language (Boston Naming Test-Short Version and Controlled Oral Word Association Test), attention (Trail Making Test A and Wechsler Adult Intelligenence Scale-IV Digit Span), comprehension (Wechsler Adult Intelligence Scale-IV), and quality of life (Functional Assessment of Cancer Therapy-Cognitive Function). Structured interviews evaluated IC and decisional capacity. Psychological measures included distress (Hospital Anxiety Depression Scale) and depression (Beck Depression Inventory-II). Results One hundred eighteen ACPs on phase I trials were evaluated, with CF ranging from mild impairment to superior performance. Only 45% of ACPs recalled physician disclosure of the phase I trial purpose. The 50% of ACPs who correctly identified the phase I research purpose had greater CF compared with ACPs who did not, as revealed by the mean T scores for memory (37.2 ± 5.6 v 32.5 ± 5.1, respectively; P = .001), attention (29 ± 2.7 v 26.9 ± 2.4, respectively; P < .001), visual attention (35.2 ± 6.6 v 31.5 ± 6.2, respectively; P = .001), and executive function (38.9 ± 7.5 v 34 ± 7.1, respectively; P < .001). Older ACPs (≥ 60 years) were less likely to recall physician disclosure of phase I purpose than younger ACPs (30% v 70%, respectively; P = .02) and had measurable deficits in total memory (34.2 ± 5.0 v 37.3 ± 5.6, respectively; P = .002), attention (24.5 ± 2.6 v 28 ± 2.8, respectively; P < .001), and executive function (32.8 ± 7.3 v 36.4 ± 7.6, respectively; P = .01). Older ACPs, compared with younger ACPs, also had greater depression scores (10.6 ± 9.2 v 8.1 ± 5.2, respectively; P = .03) and lower quality-of-life scores (152 ± 29.6 v 167 ± 20, respectively; P = .03). After adjustment by age, no psychological or neuropsychological variable was further significantly associated with likelihood of purpose identification. Conclusion CF seems to play a role in ACP recall and comprehension of IC for early-phase clinical trials, especially among older ACPs.

Ginsenoside Rb1 ameliorates cisplatin-induced learning and memory impairments

Background

Ginsenoside Rb1 (Rb1), a dominant component from the extract of Panax ginseng root, exhibits neuroprotective functions in many neurological diseases. This study was intended to investigate whether Rb1 can attenuate cisplatin-induced memory impairments and explore the potential mechanisms.

Methods

Cisplatin was injected intraperitoneally with a dose of 5 mg/kg/wk, and Rb1 was administered in drinking water at the dose of 2 mg/kg/d to rats for 5 consecutive wk. The novel objects recognition task and Morris water maze were used to detect the memory of rats. Nissl staining was used to examine the neuron numbers in the hippocampus. The activities of superoxide dismutase, glutathione peroxidase, cholineacetyltransferase, acetylcholinesterase, and the levels of malondialdehyde, reactive oxygen species, acetylcholine, tumor necrosis factor-α, interleukin-1β, and interleukin-10 were measured by ELISA to assay the oxidative stress, cholinergic function, and neuroinflammation in the hippocampus.

Results

Rb1 administration effectively ameliorates the memory impairments caused by cisplatin in both novel objects recognition task and Morris water maze task. Rb1 also attenuates the neuronal loss induced by cisplatin in the different regions (CA1, CA3, and dentate gyrus) of the hippocampus. Meanwhile, Rb1 is able to rescue the cholinergic neuron function, inhibit the oxidative stress and neuroinflammation in cisplatin-induced rat brain.

Conclusion

Rb1 rescues the cisplatin-induced memory impairment via restoring the neuronal loss by reducing oxidative stress and neuroinflammation and recovering the cholinergic neuron functions.

Predictors of cognitive decline in people with cancer undergoing chemotherapy

PURPOSE

The purpose of this study was to investigate the impact of demographic factors, disease/treatment-related factors, and psychological factors on cognitive function.

METHOD

A cross-sectional study was conducted. Participants were recruited from the oncology inpatient units of two hospitals. A convenience sample of 175 patients with cancer who underwent chemotherapy were recruited. The Everyday Cognition Scale (ECog), the Korean version of the Mini Mental State Examination (K-MMSE), Functional Assessment of Cancer Therapy-Fatigue (FACT-F) scale, Hospital Anxiety and Depression Scale (HADS), and a questionnaire to collect information about demographic, disease, and treatment information were completed.

RESULTS

More participants showed a mild decline in cognitive function and self-reported cognitive decline (39.4%) than had objectively confirmed decline (20%). Notably, 53.7-62.9% of the participants showed memory loss and a decline in divided attention. Demographic factors (age, sex), disease/treatment-related factors (chemotherapy cycles, fatigue), and psychological factors (depression) were predictors of cognitive decline in 49.6% of participants.

CONCLUSIONS

Old age and cumulative chemotherapy cycles were the main influential factors for objectively confirmed cognitive decline, and fatigue was the most common predictor of self-reported cognitive decline. Depression was one of the predictors of perceived cognitive decline, but it was not significant for objectively measured cognitive function. Thus, treatment-related factors such as fatigue had a greater impact on cognitive decline than psychological factors.

Naringin and Rutin Alleviates Episodic Memory Deficits in Two Differentially Challenged Object Recognition Tasks

Background:

Cognitive decline or dementia is a debilitating problem of neurological disorders such as Alzheimer's and Parkinson's disease, including special conditions like chemobrain. Dietary flavonoids proved to be efficacious in delaying the incidence of neurodegenerative diseases. Two such flavonoids, naringin (NAR) and rutin (RUT) were reported to have neuroprotective potential with beneficial effects on spatial and emotional memories in particular. However, the efficacy of these flavonoids is poorly understood on episodic memory, which comprises an important form of autobiographical memory.

Objective:

This study objective is to evaluate NAR and RUT to reverse time-delay-induced long-term and scopolamine-induced short-term episodic memory deficits in Wistar rats.

Materials and Methods:

We have evaluated both short-term and long-term episodic memory forms using novel object recognition task. Open field paradigm was used to assess locomotor activity for any confounding influence on memory assessment. Donepezil was used as positive control and was effective in both models at 1 mg/kg, i.p.

Results:

Animals treated with NAR and RUT at 50 and 100 mg/kg, p.o. spent significantly more time exploring novel object compared to familiar one, whereas control animals spent almost equal time with both objects in choice trial. NAR and RUT dose-dependently increased recognition and discriminative indices in time-induced long-term as well as scopolamine-induced short-term episodic memory deficit models without interfering with the locomotor activity.

Conclusion:

We conclude that, NAR and RUT averted both short- and long-term episodic memory deficits in Wistar rats, which may be potential interventions for neurodegenerative diseases as well as chemobrain condition.

SUMMARY

Incidence of Alzheimer's disease is increasing globally and the current therapy is only symptomatic. Curative treatment is a major lacuna. NAR and RUT are natural flavonoids proven for their pleiotropic pharmacological effects with potential neuroprotective benefits. The study evaluated these flavonoids for their potential to improve the most common form of episodic memory (memory of autobiographical events in relation to time, places etc.) in two differential animal models assessing short-term and long-term memory, respectively. We also found that NAR and RUT were able to reverse both short-term and long-term memory deficits dose dependently in female Wistar rats.

Abbreviations used: AD: Alzheimer's disease, AChE: Acetylcholinesterase, COX: Cyclooxygenase, DI: Discriminative index, ITI: Inter trial interval, NAR: Naringin, RUT: Rutin, NORT: Novel object recognition task, NOS: Nitric oxide synthase, QOL: Quality of life, RI: Recognition index, WFI: Water for injection

Sustained attention abnormalities in breast cancer survivors with cognitive deficits post chemotherapy: An electrophysiological study

OBJECTIVE

Many breast cancer survivors (BCS) report cognitive problems following chemotherapy, yet controversy remains concerning which cognitive domains are affected. This study investigated a domain crucial to daily function: the ability to maintain attention over time.

METHODS

We examined whether BCS who self-reported cognitive problems up to 3 years following cancer treatment (n=19) performed differently from healthy controls (HC, n=12) in a task that required sustained attention. Participants performed a target detection task while periodically being asked to report their attentional state. Electroencephalogram was recorded during this task and at rest.

RESULTS

BCS were less likely to maintain sustained attention during the task compared to HC. Further, the P3 event-related potential component elicited by visual targets during the task was smaller in BCS relative to HC. BCS also displayed greater neural activity at rest.

CONCLUSIONS

BCS demonstrated an abnormal pattern of sustained attention and resource allocation compared to HC, suggesting that attentional deficits can be objectively observed in breast cancer survivors who self-report concentration problems.

SIGNIFICANCE

These data underscore the value of EEG combined with a less traditional measure of sustained attention, or attentional states, as objective laboratory tools that are sensitive to subjective complaints of chemotherapy-related attentional impairments.

A meta-analysis of cognitive impairment and decline associated with adjuvant chemotherapy in women with breast cancer

A meta-analysis was performed to quantify the magnitude and nature of the association between adjuvant chemotherapy and performance on a range of cognitive domains among breast cancer patients. A total of 27 studies (14 cross-sectional, 8 both cross-sectional and prospective, and 5 prospective) were included in the analyses, involving 1562 breast cancer patients who had undergone adjuvant chemotherapy and 2799 controls that included breast cancer patients who did not receive adjuvant chemotherapy. A total of 737 effect sizes (Cohen's d) were calculated for cross-sectional and prospective longitudinal studies separately and classified into eight cognitive domains. The mean effect sizes varied across cross-sectional and prospective longitudinal studies (ranging from -1.12 to 0.62 and -0.29 to 1.12, respectively). Each cognitive domain produced small effect sizes for cross-sectional and prospective longitudinal studies (ranging from -0.25 to 0.41). Results from cross-sectional studies indicated a significant association between adjuvant chemotherapy and cognitive impairment that held across studies with varied methodological approaches. For prospective studies, results generally indicated that cognitive functioning improved over time after receiving adjuvant chemotherapy. Greater cognitive impairment was reported in cross-sectional studies comparing chemotherapy groups with healthy control groups. Results suggested that cognitive impairment is present among breast cancer patients irrespective of a history of chemotherapy. Prospective longitudinal research is warranted to examine the degree and persisting nature of cognitive impairment present both before and after chemotherapy, with comparisons made to participants' cognitive function prior to diagnosis. Accurate understanding of the effects of chemotherapy is essential to enable informed decisions regarding treatment and to improve quality of life among breast cancer patients.

Assessment of the feasibility of a rehabilitation intervention program for breast cancer survivors with cognitive complaints

To assess the feasibility of a cognitive rehabilitation program in breast cancer survivors (BCS) with persistent post-treatment cognitive complaints. BCS with cognitive complaints, 18-months to 5-years post-treatment, were recruited for a once-weekly, five-week, group cognitive training intervention. Outcome measures included self-reported mood and cognitive function, and neurocognitive tests administered at pre-intervention, immediate-, two-month and four-month post-intervention. A sub-study in eight participants evaluated resting state quantitative electroencephalography (qEEG) changes from pre- to immediate post-intervention in relationship to post-intervention changes in cognitive complaints. Twenty-seven BCS completed the protocol and tolerated the intervention well. We observed significant reductions in total and memory-specific cognitive complaints from pre-intervention to immediate post-intervention (p = 0.031 and p = 0.009, respectively) and at four-months post-intervention (p < 0.0001 and p < 0.001, respectively). Significant improvement in neurocognitive tests were found for Symbol Digit, Stroop, and Trails A tests (df = 26, all p's <0.05). Effect sizes for changes from pre-intervention to immediate and to four-month post intervention ranged from 0.429 to 0.607, and from 0.439 to 0.741, respectively. Increase in qEEG absolute alpha power over the course of the intervention was associated with reduced complaints at immediate post-intervention (r = -0.78, p = 0.021), two-months (r range = -0.76 to -0.82, p-value range 0.004 to 0.03), and four-months (r = -0.71, p = 0.048). A five-week group cognitive training intervention is feasible and well tolerated. Cognitive complaints and neurocognitive test performances showed positive changes. qEEG may serve as a potential biomarker for improvement in self-reported complaints. A randomized clinical trial is underway to test the efficacy of the intervention.

Integrating imaging findings in evaluating the post-chemotherapy brain

Cognitive complaints following cancer and cancer therapy are common. Many studies have investigated the effects of chemotherapy on the brain. However, the mechanisms for the associated cognitive impairment are not well understood. Some studies have also included brain imaging to investigate potential neurological substrates of cognitive changes. This review examines recent neuroimaging studies on cancer- and chemotherapy-related cognitive dysfunction in non-central nervous system cancers and compares findings across imaging modalities. Grey matter volume reductions and decreases in white matter integrity are seen after exposure to adjuvant chemotherapy for breast cancer, and functional studies have illuminated both hypo- and hyperactivations in many of the same regions months to years following therapy. These comparisons can assist in further characterizing the dysfunction reported by patients and contribute to a better understanding of the mechanisms involved.

Neural correlates of chemotherapy-related cognitive impairment

Cancer survivors frequently experience cognitive deficits following chemotherapy. The most commonly affected functions include memory, attention and executive control. The present paper reviews animal research and clinical studies including event-related potential (ERP) and neuroimaging investigations of chemotherapy-related changes of brain structure and function. In rodents, chemotherapeutic substances have been shown to damage neural precursor cells and white matter tracts and are associated with impairments of learning and memory. Structural and functional changes associated with chemotherapy have also been observed in humans. Structural imaging has revealed gray and white matter volume reductions and altered white matter microstructure. Functional studies using either ERPs or hemodynamic imaging have shown that chemotherapy alters the activation patterns of cortical networks involved in higher cognitive functions. Collectively, these findings support the existence of the "chemobrain" phenomenon beyond the patients' subjective reports. However, the rather small number of studies and methodological limitations of some of the pioneering investigations call for further research of high methodological quality, including larger numbers of subjects with appropriate controls to delineate the temporal and spatial pattern of chemotherapy-associated central nervous system (CNS) toxicity. Brain activation studies in humans might systematically vary task difficulty levels to distinguish between compensatory hyper-activations on the one hand and deficient recruitment of resources on the other hand. Integrative functions could be tested by connectivity analyses using both electrophysiological and hemodynamic measures. The ultimate goal should be the development of cognitive-behavioral and pharmacological interventions to reduce the cognitive side effects of the medically indispensable but neurotoxic chemotherapeutic treatments.

Clearing the air: a review of our current understanding of "chemo fog"

An increasing number of cancer survivors has led to a greater interest in the long-term side effects of cancer treatments and their impact on quality of life. In particular, cognitive impairments have been frequently reported by cancer survivors as an adverse effect which they attribute to the neurotoxicity of chemotherapy and have dubbed "chemobrain" or "chemo fog." Research within the past 15-20 years has explored the many factors thought to contribute to cancer-related cognitive decline in an attempt to determine a potential cause. In spite of many confounding factors, there is growing evidence that the neurotoxicity of chemotherapy does contribute to cognitive changes. This review examines the evolution of "chemo fog" research with a look at methodological issues, the status of our current understanding, and suggestions for future research.

Relationship between exercise behavior, cardiorespiratory fitness, and cognitive function in early breast cancer patients treated with doxorubicin-containing chemotherapy: a pilot study

The purpose of this study was to examine the relationship between self-reported exercise behavior, cardiorespiratory fitness (CRF), and cognitive function in early breast cancer patients. Thirty-seven breast cancer patients following completion of chemotherapy (median 16 months) and 14 controls were studied. Cognitive function was assessed using the Central Nervous System (CNS) Vital Signs software (CNS Vital Signs, LLC, Morrisville, N.C., USA), a computerized test battery consisting of 9 cognitive subtests. Exercise behavior was evaluated using the Godin Leisure Time Exercise Questionnaire, and CRF was assessed via a cardiopulmonary exercise test to assess peak oxygen consumption. Patients' mean total exercise was 184 ± 141 min·week(-1) compared with 442 ± 315 min·week(-1) in controls (p < 0.001). Significantly fewer patients (32%) were meeting exercise guidelines (i.e., ≥150 min of moderate-intensity or vigorous exercise per week) compared with 57% of controls (p = 0.014). Patients' peak oxygen consumption averaged 23.5 ± 6.3 mL·kg(-1)·min(-1) compared with 30.6 ± 7.0 mL·kg(-1)·min(-1) in controls (p < 0.01). Scores on the cognitive subdomains were generally lower in patients compared with controls, although only the difference in verbal memory was significant (unadjusted p = 0.041). In patients, weak to moderate correlations were indicated between exercise, peak oxygen consumption, and the majority of cognitive subdomain scores; however, there was a significant positive correlation between exercise and visual memory (r = 0.47, p = 0.004). In conclusion, breast cancer patients following the completion of primary adjuvant chemotherapy exhibit, in general, worse cognitive performance than healthy women from the general population, and such performance may be related to their level of exercise behavior.

Cognitive impairment in gynecologic cancers: a systematic review of current approaches to diagnosis and treatment

PURPOSE

To review the etiology and assessment of chemotherapy-related cognitive impairment (CRCI). To explore current treatment and prevention strategies for CRCI and propose future research goals in the field of gynecologic oncology.

METHODS

Computerized searches in PubMed of cognitive impairment in cancer between 2000 and 2012 were conducted. The inclusion criteria were randomized control trials evaluating treatment of CRCI and search terms 'cognitive function, cognitive impairment, cognitive decline, chemobrain, chemofog, and cancer'.

RESULTS

To date, numerous modalities have been utilized for assessing CRCI in patients undergoing therapy. It has been proposed to move towards web-based assessment modalities as a possible standard. Few studies have aimed to elucidate possible treatment and prevention options for CRCI; even less in the field of gynecologic oncology. Only seven of these studies were subjected to randomized control trials. Only one of these studies looked at treatment in patients with gynecologic cancers.

CONCLUSIONS

The etiology of CRCI is multi-factorial. Following from this, there is no consensus on the best way to assess CRCI although objective measures are more reliable. One must extrapolate data from the non-gynecologic cancer literature, even venturing to non-cancer literature, to explore the treatment and prevention of CRCI. The methods found in these areas of research have not yet been applied to CRCI in gynecologic oncology.

Cognitive complaints after breast cancer treatments: examining the relationship with neuropsychological test performance

BACKGROUND

Cognitive complaints are reported frequently after breast cancer treatments. Their association with neuropsychological (NP) test performance is not well-established.

METHODS

Early-stage, posttreatment breast cancer patients were enrolled in a prospective, longitudinal, cohort study prior to starting endocrine therapy. Evaluation included an NP test battery and self-report questionnaires assessing symptoms, including cognitive complaints. Multivariable regression models assessed associations among cognitive complaints, mood, treatment exposures, and NP test performance.

RESULTS

One hundred eighty-nine breast cancer patients, aged 21-65 years, completed the evaluation; 23.3% endorsed higher memory complaints and 19.0% reported higher executive function complaints (>1 SD above the mean for healthy control sample). Regression modeling demonstrated a statistically significant association of higher memory complaints with combined chemotherapy and radiation treatments (P = .01), poorer NP verbal memory performance (P = .02), and higher depressive symptoms (P < .001), controlling for age and IQ. For executive functioning complaints, multivariable modeling controlling for age, IQ, and other confounds demonstrated statistically significant associations with better NP visual memory performance (P = .03) and higher depressive symptoms (P < .001), whereas combined chemotherapy and radiation treatment (P = .05) approached statistical significance.

CONCLUSIONS

About one in five post-adjuvant treatment breast cancer patients had elevated memory and/or executive function complaints that were statistically significantly associated with domain-specific NP test performances and depressive symptoms; combined chemotherapy and radiation treatment was also statistically significantly associated with memory complaints. These results and other emerging studies suggest that subjective cognitive complaints in part reflect objective NP performance, although their etiology and biology appear to be multifactorial, motivating further transdisciplinary research.

Association between chemotherapy and cognitive impairments in a large cohort of patients with colorectal cancer

No population-based study has been conducted on the relationship between chemotherapy and the risk of cognitive impairments in patients with colorectal cancer. This study aimed to determine this association in a large population-based cohort of patients. We studied 72,374 men and women who were diagnosed with stages I-III colorectal cancer at age ≥ 65 years from 1991 through 2002 from 16 regions in the Surveillance, Epidemiology and End Results program who were free of cognitive impairments at baseline with up to 17 years of follow-up and also studied 15,921 matched cohorts based on the propensity of receiving chemotherapy. The cumulative incidence of drug-induced dementia at 5 years was 16.2 cases per 1,000 persons for the chemotherapy group and 12.4 cases per 1,000 persons for the no chemotherapy group. Overall, patients who received chemotherapy were 24% significantly more likely to develop drug-induced dementia compared to those without chemotherapy after adjusting for patient and tumor characteristics (hazard ratio 1.24, 95% confidence interval 1.05-1.47). The significantly increased risk was only observed in those without mood disorder who received chemotherapy in the entire cohort (1.26, 1.06-1.50) and in the matched cohort (1.29, 1.04-1.59). The risk of developing Alzheimer's disease, vascular dementia or other dementias was significantly lower in patients receiving chemotherapy compared to those without chemotherapy regardless of mood disorder status. In conclusion, there was a significant association between chemotherapy and the risk of developing drug-induced dementia in patients with colorectal cancer without mood disorder, but chemotherapy was associated with a decreased risk of other dementias.

Cognitive effects of chemotherapy in breast cancer patients: a dose-response study

OBJECTIVE

The purpose of this study was to determine if cognition progressively worsens with cumulative chemotherapy exposure. We reasoned that the demonstration of such a 'dose-response' relationship would help to establish whether cognitive changes are caused by neurotoxic effects of chemotherapy or whether they are due to other confounding factors such as mood and pre-treatment differences in cognition.

METHODS

Sixty women with early stage breast cancer, aged 65 years or younger with no previous history of cancer or chemotherapy, were matched to 60 healthy women on age and education. Neuropsychological assessment was conducted after surgery but prior to commencing chemotherapy and then again following each chemotherapy cycle in patients and at yoked intervals in healthy controls. We used multilevel modeling to assess change over time in an overall cognitive summary score as well as domain-specific cognitive scores.

RESULTS

After controlling for baseline performance, age, education, and mood, the chemotherapy group showed a significant progressive decline over time relative to a matched healthy control group in an overall cognitive summary score, as well as in working memory, processing speed, verbal memory, and visual memory scores. A linear model best fit the trajectory of cognitive change over the course of treatment in the chemotherapy group supporting a dose-response hypothesis.

CONCLUSIONS

These results are in keeping with a dose-response relationship and provide the most compelling clinical evidence to date that cognitive decline is caused by chemotherapy exposure.

Meta-analysis of cognitive functioning in breast cancer survivors previously treated with standard-dose chemotherapy

PURPOSE

Evidence is mixed regarding long-term cognitive deficits in patients treated with chemotherapy. Previous meta-analyses have not focused specifically on the postchemotherapy period and have not incorporated several recent studies. The goal of the current study was to conduct a meta-analysis of cognitive functioning in breast cancer survivors who were treated with chemotherapy ≥ 6 months previously.

METHODS

A search of PubMed, PsycInfo, Cumulative Index to Nursing and Allied Health Literature, and Cochrane Library yielded 2,751 abstracts, which were independently evaluated by pairs of raters. Meta-analysis was conducted on 17 studies of 807 patients previously treated with standard-dose chemotherapy for breast cancer. Neuropsychological tests were categorized according to eight cognitive domains: attention, executive functioning, information processing, motor speed, verbal ability, verbal memory, visual memory, and visuospatial ability.

RESULTS

Deficits in cognitive functioning were observed in patients treated with chemotherapy relative to controls or prechemotherapy baseline in the domains of verbal ability (g = -0.19; P < .01) and visuospatial ability (g = -0.27; P < .01). Patients treated with chemotherapy performed worse than noncancer controls in verbal ability and worse than patients treated without chemotherapy in visuospatial ability (both P < .01). Age, education, time since treatment, and endocrine therapy did not moderate observed cognitive deficits in verbal ability or visuospatial ability (all P ≥ .51).

CONCLUSION

Results indicate that, on average, observed cognitive deficits in patients with breast cancer previously treated with chemotherapy are small in magnitude and limited to the domains of verbal ability and visuospatial ability. This information can be used to inform interventions to educate patients with breast cancer regarding the long-term impact of chemotherapy on cognitive functioning.

An evaluation on the neuropsychological tests used in the assessment of postchemotherapy cognitive changes in breast cancer survivors

OBJECTIVES

The choice of appropriate neuropsychological tests is important in evaluating the onset, severity, duration, and site of cognitive changes in postchemotherapy breast cancer survivors. This literature review is designed to evaluate and provide a summary of suitable neuropsychological tests to determine cognitive changes in breast cancer survivors.

METHOD

A literature search restricted to publications in English before June 2011 was performed using the following combination of keywords: "neuropsychological assessments," "breast cancer," "chemotherapy," and "cognitive impairment." Only observational studies that performed cognitive assessments on breast cancer survivors were included. The neuropsychological assessments were grouped as "objective" (traditional batteries and screening tests), "subjective," or "computerized."

RESULTS

Of the 43 studies extracted, memory (88 %) and attention/concentration (88 %) are the two most commonly assessed domains. A majority (63 %) employed the use of Wechsler Adult Intelligent Scale (an objective test), while only 49 % incorporated subjective assessments to assess perceived cognitive impairment. Computerized tests received low popularity (28 %) despite their numerous advantages, which include overcoming the language- and cultural-dependent limitations of traditional objective tests.

CONCLUSIONS

In the selection of a suitable neuropsychological tool to determine the onset, severity, site, and duration of cognitive changes in breast cancer survivors, incorporation of both subjective and objective tests is essential to facilitate a comprehensive assessment. With more validation work performed in future studies, it may be feasible to employ computerized neuropsychological assessments in both clinical and research settings.

Global effects of adriamycin treatment on mouse splenic protein levels

Adriamycin (ADR) is a potent anticancer drug used to treat a variety of cancers. Patients treated with ADR have experienced side effects such as heart failure, cardiomyopathy, and "chemobrain", which have been correlated to changes in protein expression in the heart and brain. In order to better understand cellular responses that are disrupted following ADR treatment in immune tissues, this work focuses on spleen. Significantly reduced spleen sizes were found in ADR-treated mice. Global isotopic labeling of tryptic peptides and nanoflow reversed-phase liquid chromatography-tandem mass spectrometry (LC-MS/MS) were employed to determine differences in the relative abundances of proteins from ADR-treated mice relative to controls. Fifty-nine proteins of the 388 unique proteins identified showed statistically significant differences in expression levels following acute ADR treatment. Differentially expressed proteins are involved in processes such as cytoskeletal structural integrity, cellular signaling and transport, transcription and translation, immune response, and Ca(2+) binding. These are the first studies to provide insight to the downstream effects of ADR treatment in a peripheral immune organ such as spleen using proteomics.

Longitudinal assessment of chemotherapy-induced structural changes in cerebral white matter and its correlation with impaired cognitive functioning

PURPOSE

To uncover the neural substrate of cognitive impairment related to adjuvant chemotherapy, we studied cerebral white matter (WM) integrity before and after chemotherapy by using magnetic resonance diffusion tensor imaging (DTI) in combination with detailed cognitive assessment.

PATIENTS AND METHODS

Thirty-four young premenopausal women with early-stage breast cancer who were exposed to chemotherapy underwent neuropsychologic testing and DTI before the start of chemotherapy (t1) and 3 to 4 months after treatment (t2). Sixteen patients not exposed to chemotherapy and 19 age-matched healthy controls underwent the same assessment at matched intervals. In all groups, we used paired t tests to study changes in neuropsychologic test scores and whole-brain voxel-based paired t tests to study changes in WM fractional anisotropy (FA; a DTI measure that reflects WM tissue organization), with depression scores and intelligence quotient as included covariates. We correlated changes of neuropsychologic test scores with the mean change of FA for regions that survived the paired t tests in patients treated with chemotherapy.

RESULTS

In contrast to controls, the chemotherapy-treated group performed significantly worse on attention tests, psychomotor speed, and memory at t2 compared with t1 (P < .05). In the chemotherapy-treated group, we found significant decreases of FA in frontal, parietal, and occipital WM tracts after treatment (familywise error P < .05), whereas for both control groups, FA values were the same between t1 and t2. Furthermore, performance changes in attention and verbal memory correlated with mean regional FA changes in chemotherapy-treated patients (P < .05).

CONCLUSION

We report evidence of longitudinal changes in cognitive functioning and cerebral WM integrity after chemotherapy as well as an association between both.

The effect of cigarette smoking on cancer treatment-related side effects

BACKGROUND

Cigarette smoking has long been implicated in cancer development and survival. However, few studies have investigated the impact of smoking on symptom burden in cancer survivors during treatment and at survivorship stage. This study examines the influence of cigarette smoking on side effects among 947 cancer patients during and 6 months following treatment.

METHODS

Patients diagnosed with cancer and scheduled to receive chemotherapy and/or radiation therapy reported on current smoking status (yes, no) and total symptom burden [the sum of 12 common symptoms (fatigue, hair loss, memory, nausea, depression, sleep, pain, concentration, hot flashes, weight loss, skin problems, and dyspnea) scored on an 11-point scale ranging from 0 = "not present" to 10 = "as bad as you can imagine"] during treatment and at 6-month follow-up. The adjusted mean total symptom burden by smoking status was determined by analysis of covariance controlling for age, gender, race, education, occupation, treatment, cancer site, and Karnofsky performance score.

RESULTS

During treatment, smokers (S) had a significantly higher total symptom burden than nonsmokers (NS) (S = 46.3 vs. NS = 41.2; p < 0.05). At 6-month follow-up, smokers continued to report a higher total symptom burden than nonsmokers (S = 27.7 vs. NS = 21.9; p < 0.05). Participants who quit smoking before treatment levels had a total symptom burden similar to nonsmokers.

CONCLUSION

Smoking was associated with an increased symptom burden during and following treatments for cancer. Targeted cessation efforts for smokers to decrease symptom burden may limit the likelihood of treatment interruptions and increase quality of life following treatment.

Long-term cognitive impairment in older adult twins discordant for gynecologic cancer treatment

BACKGROUND

Research has found that patients treated for cancer generally have an increased risk for cognitive problems. However, many studies have focused on cognitive performance of cancer patients under the age of 65 who received chemotherapy treatment. Less studied is the extent to which cancer diagnosis may be associated with cognitive impairment as a late effect for older adults.

METHODS

In this retrospective, co-twin design study, twin pairs 65 years of age and older discordant for cancer were identified from the Swedish Twin Registry. A pair was included if both twins participated in cognitive screening, and the twin with the cancer history was screened at least 3 years after cancer diagnosis and treatment.

RESULTS

Female, but not male, survivors of cancer were significantly (odds ratio = 2.42, 95% confidence interval = 1.23-4.74) more likely to exhibit cognitive impairment 3 or more years after cancer diagnosis and treatment as their co-twin without a history of cancer. In particular, risk was higher among survivors of gynecologic cancers (odds ratio = 10.00, 95% confidence interval = 1.28-78.11) and those who had treatments directly or potentially affecting ovarian functioning (odds ratio = 13.00, 95% confidence interval = 1.70-99.36) compared with their respective co-twins.

CONCLUSIONS

These findings suggest that localized treatments and other cancer-related factors should be explored as determinants that underlie the association between cancer diagnosis and long-term cognitive impairment.

An update on cancer- and chemotherapy-related cognitive dysfunction: current status

The purpose of this review is to summarize the current literature on the effects of cancer treatment-related cognitive difficulties, with a focus on the effects of chemotherapy. Numerous patients have cognitive difficulties during and after cancer treatments and, for some, these effects last years after treatment. We do not yet fully understand which factors increase susceptibility to cognitive difficulties during treatment and which cause persistent problems. We review possible contributors, including genetic and biological factors. Mostly we focus is on cognitive effects of adjuvant chemotherapy for breast cancer; however, cognitive effects of chemotherapy on the elderly and brain tumor patients are also discussed.

Either called "chemobrain" or "chemofog," the long-term chemotherapy-induced cognitive decline in cancer survivors is real

CONTEXT

In recent years, there is growing evidence in the medical literature to support an association between administration of commonly used chemotherapeutic agents and an increased risk for cognitive impairment.

OBJECTIVES

We herein critically summarize data relating to the pathophysiological mechanisms by which chemotherapy may induce cognitive impairment in patients surviving from solid tumors. The clinical and epidemiological characteristics and the proposed management strategies to counter chemotherapy-induced cognitive impairment (CICI) also are presented.

METHODS

References for this review were identified by searches of PubMed from 1995 until December 2009 with related terms.

RESULTS

Both the pathogenetic mechanisms and the overall clinical nature of CICI remain vaguely defined. Findings indicate that CICI is a relatively common event that, in most of the cases, remains underdiagnosed, thereby adversely affecting the quality of life of patients with cancer. Effective pharmacological interventions toward the symptomatic or prophylactic management of CICI also are lacking.

CONCLUSION

Either called "chemobrain" or "chemofog," the long-term CICI in cancer survivors is real. The need for multidisciplinary care interventions toward a timely diagnosis and management of CICI is clearly warranted.

Doxorubicin-induced central nervous system toxicity and protection by xanthone derivative of Garcinia mangostana

Doxorubicin (Dox) is a potent, broad-spectrum chemotherapeutic drug used around the world. Despite its effectiveness, it has a wide range of toxic side effects, many of which most likely result from its inherent pro-oxidant activity. It has been reported that Dox has toxic effects on normal tissues, including brain tissue. The present study tested the protective effect of a xanthone derivative of Garcinia Mangostana against Dox-induced neuronal toxicity. Xanthone can prevent Dox from causing mononuclear cells to increase the level of tumor necrosis factor-alpha (TNFα). We show that xanthone given to mice before Dox administration suppresses protein carbonyl, nitrotyrosine and 4-hydroxy-2'-nonenal (4HNE)-adducted proteins in brain tissue. The levels of the pro-apoptotic proteins p53 and Bax and the anti-apoptotic protein Bcl-xL were significantly increased in Dox-treated mice compared with the control group. Consistent with the increase of apoptotic markers, the levels of caspase-3 activity and TUNEL-positive cells were also increased in Dox-treated mice. Pretreatment with xanthone suppressed Dox-induced increases in all indicators of injury tested. Together, the results suggest that xanthone prevents Dox-induced central nervous system toxicity, at least in part, by suppression of Dox-mediated increases in circulating TNFα. Thus, xanthone is a good candidate for prevention of systemic effects resulting from reactive oxygen generating anticancer therapeutics.

Breast cancer treatment and cognitive function: the current state of evidence, underlying mechanisms and potential treatments

Within the last decade, several studies have investigated whether adjuvant treatment of breast cancer affects cognitive function. A number of prospective studies have demonstrated inconsistent results regarding whether chemotherapy affects cognitive function. Approximately half of the studies demonstrated subtle cognitive decline in a wide range of domains among some breast cancer patients following chemotherapy, and half did not. Concomitant changes in brain structure and function have been identified in neuroimaging and neurophysiologic studies. Estrogenic therapy has been specifically associated with deterioration in verbal memory and processing speed. However, evidence is mostly based on smaller studies with cross-sectional data. Breast cancer patients who underwent both chemotherapy and estrogenic therapy showed the most deterioration and the most persistent decline in cognitive function. Since cognitive impairment is subtle, if evident at all, discrepant findings are due to hormonal, physiological, psychological or temporal confounding variables and differences in study design. Neuropsychological training has been demonstrated to improve cognitive dysfunction experienced by breast cancer patients after chemotherapy. Future research may examine the unique impact of endocrine therapy on cognitive function with prospective, controlled trials, as well as the role of further confounding variables (e.g., menopausal status, cytokine deregulation, cortisol and concurrent medication).

Cerebral hyporesponsiveness and cognitive impairment 10 years after chemotherapy for breast cancer

Chemotherapy is associated with cognitive impairment in a subgroup of breast cancer survivors, but the neural circuitry underlying this side effect is largely unknown. Moreover, long-term impairment has not been studied well. In the present study, functional magnetic resonance imaging (fMRI) and neuropsychological testing were performed in breast cancer survivors almost 10 years after high-dose adjuvant chemotherapy (chemo group, n = 19) and in breast cancer survivors for whom chemotherapy had not been indicated (control group, n = 15). BOLD activation and performance were measured during an executive function task involving planning abilities (Tower of London) and a paired associates task for assessment of episodic memory. For the chemo group versus the control group, we found hyporesponsiveness of dorsolateral prefrontal cortex in the Tower of London, and of parahippocampal gyrus in the paired associates task. Also, the chemo group showed significantly impaired planning performance and borderline significantly impaired recognition memory as compared to findings in the control group. Whole-brain analyses demonstrated hyporesponsiveness of the chemo versus the control group in very similar regions of bilateral posterior parietal cortex during both the Tower of London and the paired associates task. Neuropsychological testing showed a relatively stable pattern of cognitive impairment in the chemo group over time. These results indicate that high-dose adjuvant chemotherapy is associated with long-term cognitive impairments. These impairments are underpinned by (a) task-specific hyporesponsiveness of dorsolateral prefrontal cortex and parahippocampal gyrus, and (b) a generalized hyporesponsiveness of lateral posterior parietal cortex encompassing attentional processing.

Alterations in brain antioxidant enzymes and redox proteomic identification of oxidized brain proteins induced by the anti-cancer drug adriamycin: implications for oxidative stress-mediated chemobrain

Adriamycin (ADR) is a chemotherapeutic for the treatment of solid tumors. This quinone-containing anthracycline is well known to produce large amounts of reactive oxygen species (ROS) in vivo. A common complaint of patients undergoing long-term treatment with ADR is somnolence, often referred to as "chemobrain." While ADR itself does not cross the blood brain barrier (BBB), we recently showed that ADR administration causes a peripheral increase in tumor necrosis factor alpha (TNF-alpha), which migrates across the BBB and leads to inflammation and oxidative stress in brain, most likely contributing to the observed decline in cognition. In the current study, we measured levels of the antioxidant glutathione (GSH) in brains of mice injected intraparitoneally (i.p.) with ADR, as well as the levels and activities of several enzymes involved in brain GSH metabolism. We observed significantly decreased GSH levels, as well as altered GSH/GSSG ratio in brains of ADR treated mice relative to saline-treated controls. Also observed in brains of ADR treated mice were increased levels of glutathione peroxidase (GPx), glutathione-S-transferase (GST), and glutathione reductase (GR). We also observed increased activity of GPx, but a significant reduction in GST and GR activity in mice brain, 72 h post i.p. injection of ADR (20 mg/kg body weight). Furthermore, we used redox proteomics to identify specific proteins that are oxidized and/or have differential levels in mice brains as a result of a single i.p. injection of ADR. Visinin like protein 1 (VLP1), peptidyl prolyl isomerase 1 (Pin1), and syntaxin 1 (SYNT1) showed differential levels in ADR treated mice relative to saline-treated controls. Triose phosphate isomerase (TPI), enolase, and peroxiredoxin 1 (PRX-1) showed significantly increased specific carbonylation in ADR treated mice brain. These results further support the notion ADR induces oxidative stress in brain despite not crossing the BBB, and that antioxidant intervention may prevent ADR-induced cognitive dysfunction.

Chemo brain (chemo fog) as a potential side effect of doxorubicin administration: role of cytokine-induced, oxidative/nitrosative stress in cognitive dysfunction

Doxorubicin (ADRIAMYCIN, RUBEX) is a chemotherapeutic agent that is commonly administered to breast cancer patients in standard chemotherapy regimens. As true of all such therapeutic cytotoxic agents, it can damage normal, noncancerous cells and might affect biochemical processes in a manner that might lead to, or contribute to, chemotherapy-induced cognitive deficits when administered either alone or in combination with other agents.