Cognitive impairments and cancer chemotherapy: translational research at a crossroads

The effect of doxorubicin or cyclophosphamide treatment on auditory brainstem response in mice

Clinical studies suggest that chemotherapy is associated with long-term cognitive impairment in some patients. Several underlying mechanisms have been proposed; however, the etiology of chemotherapy-related cognitive dysfunction remains relatively unknown. There is evidence that oligodendrocytes and white matter tracts within the CNS may be particularly vulnerable to chemotherapy-related damage and dysfunction. Auditory brainstem responses (ABRs) have been used to detect and measure functional integrity of myelin in a variety of animal models of autoimmune disorders and demyelinating diseases. Limited evidence suggests that increases in interpeak latencies, associated with disrupted impulse conduction, can be detected in ABRs following 5-fluorouracil administration in mice. It is unknown if similar functional disruptions can be detected following treatment with other chemotherapeutic compounds and the extent to which alterations in ABR signals represent robust and long-lasting impairments associated with chemotherapy-related cognitive impairment. Thus, C57BL/6 J mice were treated every 3rd day for a total of 3 injections with low or high dose cyclophosphamide, or doxorubicin. ABRs of mice were assessed on days 1, 7, 14, 56 and 6 months following completion of chemotherapy administration. There were timing and amplitude differences in the ABRs of the doxorubicin and the high dose cyclophosphamide groups relative to the control animals. However, despite significant toxic effects as assessed by weight loss, the changes in the ABR were transient.

The validation of a newly developed Arabic scale to assess patient-reported side-effects of antineoplastic agents

Background

Multiple scales in different languages were developed to measure patient-reported side effects of antineoplastics. However, these scales vary in their coverage of antineoplastics’ side effects, and none of them address both the severity and impact of antineoplastics’ side effects on patient quality of life. Hence, there is a need to develop a comprehensive, concise, and general scale to assess patients’ perceptions of both severity and impact of the commonly reported side effects of antineoplastics on patients’ activities of daily living and make it available in Arabic.

Objectives

To develop and validate a new scale in Arabic to assess patient-reported antineoplastics’ side-effects among Arabic-speaking patients undergoing chemotherapy.

Methods

A new scale was developed in Arabic that addresses 40 different emotional, cognitive, and physical side-effects of antineoplastics. The Antineoplastic Side effects Scale (ASES) contained three subscales focused on the side effects frequency, severity, and interference with patients’ activities of daily living. Seventy-eight patients with different cancer types were recruited from the oncology clinics of a university-affiliated tertiary care hospital in Riyadh, Saudi Arabia. The reliability of the questionnaire was examined using Cronbach’s alpha method. The construct validity was examined using principal component analysis with varimax rotation. The association between the scores of ASES subscales and various patient medical and sociodemographic characteristics were also examined.

Results

The mean age of participants was 53.8 (12.5) years and most of them were female (65.3%) and married (84.6%). The ASES demonstrated good internal consistency (Cronbach’s alpha = 0.91). The severity of the perceived side effects and their impact on activities of daily living were positively associated with female gender.

Conclusion

The newly developed ASES demonstrated good validity and reliability. This tool will hopefully help healthcare providers and patients to identify commonly reported antineoplastic side effects.

Future considerations for pediatric cancer survivorship: Translational perspectives from developmental neuroscience

Breakthroughs in modern medicine have increased pediatric cancer survival rates throughout the last several decades. Despite enhanced cure rates, a subset of pediatric cancer survivors exhibit life-long psychological side effects. A large body of work has addressed potential mechanisms for secondary symptoms of anxiety, post-traumatic stress, impaired emotion regulation and cognitive deficits in adults. Yet, absent from many studies are the ways in which cancer treatment can impact the developing brain. Additionally, it remains less known whether typical neurobiological changes during adolescence and early adulthood may potentially buffer or exacerbate some of the known negative cancer survivorship outcomes. This review highlights genetic, animal, and human neuroimaging research across development. We focus on the neural circuitry associated with aversive learning, which matures throughout childhood, adolescence and early adulthood. We argue that along with other individual differences, the precise timing of oncological treatment insults on such neural circuitry may expose particular vulnerabilities for pediatric cancer patients. We also explore other moderators of treatment outcomes, including genetic polymorphisms and neural mechanisms underlying memory and cognitive control. We discuss how neural maturation extending into young adulthood may also provide a sensitive period for intervention to improve psychological and cognitive outcomes in pediatric cancer survivors.

Impact of Cognitive Impairment in Patients with Gliomas

OBJECTIVES

To address the estimated rates of incidence, potential underlying etiologies, and cognitive domains affected from diagnosis and treatment. To describe potential cognitive function interventions.

DATA SOURCES

PubMed.

CONCLUSION

Adults with gliomas report that the most distressing, persistent, and greatest negative impact on their lives relates to the cognitive impairment they experience. However, there are several potential interventions that may prevent cognitive decline during treatment or maintain cognitive function long term.

IMPLICATIONS FOR NURSING PRACTICE

Awareness of cognitive sequela that adults with gliomas face can lead to early identification, full neurocognitive profiling, and implementation of evidence-based interventions for those experiencing cognitive impairments following cancer treatment.

KU32 prevents 5-fluorouracil induced cognitive impairment

Chemotherapy induced cognitive impairment (i.e. chemobrain) involves acute and long-term deficits in memory, executive function, and processing speed. Animal studies investigating these cognitive deficits have had mixed results, potentially due to variability in the complexity of behavioral tasks across experiments. Further, common chemotherapy treatments such as 5-fluorouracil (5-FU) break down myelin integrity corresponding to hippocampal neurodegenerative deficits and mitochondrial dysfunction. There is little evidence, however, of pharmacological treatments that may target mitochondrial dysfunction. Using a differential reinforcement of low rates (DRL) task combining spatial and temporal components, the current study evaluated the preventative effects of the pharmacological agent KU32 on the behavior of rats treated with 5-FU (5-FU+Saline vs. 5FU+KU32). DRL performance was analyzed the day after the first set of injections (D1), the day after the second set of injections (D7) and the last day of the experiment (D14). The 5FU+KU32 group earned significantly more reinforcers on the DRL task at D7 and D14 than the 5FU+Saline group. Further, the 5FU+KU32 group showed significantly better temporal discrimination. The 5FU+KU32 showed within-group improvement in temporal discrimination from D7 to D14. No significant differences were observed in spatial discrimination, however, those in the 5FU+Saline group responded more frequently on T3 compared to the 5FU+KU32 group, highlighting temporal discrimination differences between groups. The current data suggest that KU32 shows promise in the prevention of chemotherapy induced impairments in temporal discrimination.

Altered resting-state hippocampal functional networks associated with chemotherapy-induced prospective memory impairment in breast cancer survivors

In this study, we aimed to investigate the intrinsic hippocampal functional connectivity (FC) network and its relationship with prospective memory in patients with breast cancer suffering from chemotherapy-induced cognitive impairment (CICI). Thirty-four breast cancer patients before and after adjuvant chemotherapy (CB and CC, respectively) and 31 age- and education-matched cognitively normal (CN) women were recruited and subjected to a prospective memory task and a resting-state functional magnetic resonance imaging scan. Seed-based functional connectivity analysis was used to compare the hippocampal FC networks between CC and CN groups. Partial correction analysis was used to examine the association between the hippocampal FC network and prospective memory in the CC group. The cancer group that underwent chemotherapy obtained significantly poorer scores than the CN group on mini-mental state examination, verbal fluency test, digit span, and prospective memory examination. Compared to the CN group, CC group showed increased hippocampal connectivity in the frontal and parietal cortex, precuneus, posterior cingulate cortex, and the cerebellum. In addition, the increasing hippocampal FC networks were negatively correlated with prospective memory performance in the CC group. These findings suggest maladaptive hippocampal functioning as a mechanism underlying the impairment of prospective memory in patients experiencing CICI.

Effective PI3K modulators for improved therapy against malignant tumors and for neuroprotection of brain damage after tumor therapy (Review)

Due to the key role in various cellular processes including cell proliferation and cell survival on many cell types, dysregulation of the PI3K/AKT pathway represents a crucial step of the pathogenesis in many diseases. Furthermore, the tumor suppressor PTEN negatively regulates the PI3K/AKT pathway through its lipid phosphatase activity, which is recognized as one of the most frequently deleted and/or mutated genes in human cancer. Given the pervasive involvement of this pathway, the development of the molecules that modulate this PI3K/AKT signaling has been initiated in studies which focus on the extensive effective drug discovery. Consequently, the PI3K/AKT pathway appears to be an attractive pharmacological target both for cancer therapy and for neurological protection necessary after the therapy. A better understanding of the molecular relations could reveal new targets for treatment development. We review recent studies on the features of PI3K/AKT and PTEN, and their pleiotropic functions relevant to the signaling pathways involved in cancer progress and in neuronal damage by the therapy.

Impaired Brain Dopamine and Serotonin Release and Uptake in Wistar Rats Following Treatment with Carboplatin

Chemotherapy-induced cognitive impairment, known also as “chemobrain”, is a medical complication of cancer treatment that is characterized by a general decline in cognition affecting visual and verbal memory, attention, complex problem solving skills, and motor function. It is estimated that one-third of patients who undergo chemotherapy treatment will experience cognitive impairment. Alterations in the release and uptake of dopamine and serotonin, central nervous system neurotransmitters that play important roles in cognition, could potentially contribute to impaired intellectual performance in those impacted by chemobrain. To investigate how chemotherapy treatment affects these systems, fast-scan cyclic voltammetry (FSCV) at carbon-fiber microelectrodes was used to measure dopamine and serotonin release and uptake in coronal brain slices containing the striatum and dorsal raphe nucleus, respectively. Measurements were taken from rats treated weekly with selected doses of carboplatin and from control rats treated with saline. Modeling the stimulated dopamine release plots revealed an impairment of dopamine release per stimulus pulse (80% of saline control at 5 mg/kg and 58% at 20 mg/kg) after 4 weeks of carboplatin treatment. Moreover, V_max, the maximum uptake rate of dopamine, was also decreased (55% of saline control at 5 mg/kg and 57% at 20 mg/kg). Nevertheless, overall dopamine content, measured in striatal brain lysates by high performance liquid chromatography, and reserve pool dopamine, measured by FSCV after pharmacological manipulation, did not significantly change, suggesting that chemotherapy treatment selectively impairs the dopamine release and uptake processes. Similarly, serotonin release upon electrical stimulation was impaired (45% of saline control at 20 mg/kg). Measurements of spatial learning discrimination were taken throughout the treatment period and carboplatin was found to alter cognition. These studies support the need for additional neurochemical and behavioral analyses to identify the underlying mechanisms of chemotherapy-induced cognitive disorders.

Assessment of cognitive safety in clinical drug development

Cognitive impairment is increasingly recognised as an important potential adverse effect of medication. However, many drug development programmes do not incorporate sensitive cognitive measurements. Here, we review the rationale for cognitive safety assessment, and explain several basic methodological principles for measuring cognition during clinical drug development, including study design and statistical analysis, from Phase I through to postmarketing. The crucial issue of how cognition should be assessed is emphasized, especially the sensitivity of measurement. We also consider how best to interpret the magnitude of any identified effects, including comparison with benchmarks. We conclude by discussing strategies for the effective communication of cognitive risks.

Chemotherapy, cognitive impairment and hippocampal toxicity

Cancer therapies can be associated with significant central nervous system (CNS) toxicity. While radiation-induced brain damage has been long recognized both in pediatric and adult cancer patients, CNS toxicity from chemotherapy has only recently been acknowledged. Clinical studies suggest that the most frequent neurotoxic adverse effects associated with chemotherapy include memory and learning deficits, alterations of attention, concentration, processing speed and executive function. Preclinical studies have started to shed light on how chemotherapy targets the CNS both on cellular and molecular levels to disrupt neural function and brain plasticity. Potential mechanisms include direct cellular toxicity, alterations in cellular metabolism, oxidative stress, and induction of pro-inflammatory processes with subsequent disruption of normal cellular and neurological function. Damage to neural progenitor cell populations within germinal zones of the adult CNS has been identified as one of the key mechanisms by which chemotherapy might exert long-lasting and progressive neurotoxic effects. Based on the important role of the hippocampus for maintenance of brain plasticity throughout life, several experimental studies have focused on the study of chemotherapy effects on hippocampal neurogenesis and associated learning and memory. An increasing body of literature from both animal studies and neuroimaging studies in cancer patients suggests a possible relationship between chemotherapy induced hippocampal damage and the spectrum of neurocognitive deficits and mood alterations observed in cancer patients. This review aims to briefly summarize current preclinical and neuroimaging studies that are providing a potential link between the neurotoxic effects of chemotherapy and hippocampal dysfunction, highlighting challenges and future directions in this field of investigation.

Stem cell transplantation reverses chemotherapy-induced cognitive dysfunction

The frequent use of chemotherapy to combat a range of malignancies can elicit severe cognitive dysfunction often referred to as "chemobrain," a condition that can persist long after the cessation of treatment in as many as 75% of survivors. Although cognitive health is a critical determinant of therapeutic outcome, chemobrain remains an unmet medical need that adversely affects quality of life in pediatric and adult cancer survivors. Using a rodent model of chemobrain, we showed that chronic cyclophosphamide treatment induced significant performance-based decrements on behavioral tasks designed to interrogate hippocampal and cortical function. Intrahippocampal transplantation of human neural stem cells resolved all cognitive impairments when animals were tested 1 month after the cessation of chemotherapy. In transplanted animals, grafted cells survived (8%) and differentiated along neuronal and astroglial lineages, where improved cognition was associated with reduced neuroinflammation and enhanced host dendritic arborization. Stem cell transplantation significantly reduced the number of activated microglia after cyclophosphamide treatment in the brain. Granule and pyramidal cell neurons within the dentate gyrus and CA1 subfields of the hippocampus exhibited significant reductions in dendritic complexity, spine density, and immature and mature spine types following chemotherapy, adverse effects that were eradicated by stem cell transplantation. Our findings provide the first evidence that cranial transplantation of stem cells can reverse the deleterious effects of chemobrain, through a trophic support mechanism involving the attenuation of neuroinflammation and the preservation host neuronal architecture.

Effects of sertraline on executive function and quality of life in patients with advanced cancer

Background

The aim of this study was to investigate effects of the antidepressant sertraline on executive function and quality of life in patients with advanced cancer.

Material/Methods

We assigned 122 patients with stage III or IV cancer to the depressed group (DG, n=86) or the non-depressed group (NG, n=36). All subjects were given supportive treatment and patients in the DG received additional antidepressant treatment.

Results

There were significant differences in total scores of the Hamilton anxiety scale (HAMA) and the Hamilton depression scale (HAMD), performance in the Wisconsin card sorting test, and SF-36 domains. After antidepressant treatment, the level of depression and anxiety decreased significantly in the DG, but was still significantly higher than in the NG. Low executive function was enhanced in the DG, but a worsening executive function was found in total errors in the NG (−2.3±3.8) (P<0.05). The dimensions of SF-36 in physical functioning (PF), role limitations-physical (RP), bodily pain (BP), general health (GH), vitality (VT), social functioning (SF), role limitations-emotional (RE), and mental health (MH) were decreased significantly at baseline in the DG compared to the NG (P<0.01). After 12-week Sertraline treatment, improvement in the DG in factors VT, SF, RE, and MH were more powerful than in the NG (P<0.05). HAMA, HAMD, and VAS scores and tumor stage were significantly correlated to any one dimension of quality of life.

Conclusions

Depression is an important cause of decreased quality of life and executive function in patients with advanced cancer. The antidepressant sertraline can improve the executive function and quality of life, which may be helpful in the clinical practice of cancer treatment.

Cognition in breast cancer survivors: hormones versus depression

BACKGROUND

OBJECTIVE

Breast cancer survivors receiving hormone treatment and/or endorsing histories of receiving chemotherapy report changes in their cognitive capacity, which is often not supported by formal testing. To address these conflicting reports, this study examined survivors' applied cognitive capacity and its association with hormone treatment, depression, and selected demographics.

METHODS

A descriptive, correlational, cross-sectional survey design was employed. There were 357 women who completed a survey comprised of 69 questions. The survey included both investigator-developed questions and instruments from the PROMIS(®) system.

RESULTS

There were significant main effects for hormone therapy, race, and depression. Depression explained the largest portion of variance of the perceived decreases in cognitive function among breast cancer survivors.

CONCLUSIONS

Survivor complaints of changes in cognitive function may be a predictor for evaluating the presence of mood disorders and less a function of hormone therapy or chemotherapy history.