Cognitive dysfunction and chemotherapy: neuropsychological findings in perspective

Overview of cisplatin-induced neurotoxicity and ototoxicity, and the protective agents

Cisplatin has dramatically improved the survival rate of cancer patients, but it has also increased the prevalence of hearing and neurological deficits in this population. Cisplatin induces ototoxicity, peripheral (most prevalent) and central (rare) neurotoxicity. This review addresses the ototoxicity and the neurotoxicity associated with cisplatin-based chemotherapy, providing an integrated view of the potential protective agents that have been evaluated in vitro, in vivo and in clinical trials, their targets and mechanisms of protection and their effects on the antitumor activity of cisplatin. So far, the findings are insufficient to support the use of any oto- or neuroprotective agent before, during or after cisplatin chemotherapy. Despite their promising effects in vitro and in animal studies, many agents have not been evaluated in clinical trials. Additionally, the clinical trials have limitations concerning the sample size, controls, measurement, heterogeneous groups, several arms of treatment, short follow-up or no blinding. Besides that, for most agents, the effects on the antitumor activity of cisplatin have not been evaluated in tumor-bearing animals, which discourages clinical trials. Further well-designed randomized controlled clinical trials are necessary to definitely demonstrate the effectiveness of the oto- or neuroprotective agents proposed by animal and in vitro studies.

Does Shared Decision Making in Cancer Treatment Improve Quality of Life? A Systematic Literature Review

Background. The growing consensus espousing the use of shared decision making (SDM) in cancer treatment has coincided with the rise of health care evaluation paradigms that emphasize quality of life (QOL) as a central outcome measure. This review systematically examines the association between treatment SDM and QOL outcomes in cancer. Methods. A range of bibliographic databases and gray literature sources was searched. The search retrieved 16,726 records, which were screened by title, abstract, and full text to identify relevant studies. The review included 17 studies with a range of study designs and populations. Data were extracted on study methods, participants, setting, study or intervention description, outcomes, main findings, secondary findings, and limitations. Quality appraisal was used, in conjunction with a narrative approach, to synthesize the evidence. Results. The review found weak, but suggestive, evidence for a positive association between perceived patient involvement in decision making, a central dimension of SDM, and QOL outcomes in cancer. The review did not find evidence for an inverse association between SDM and QOL. The poor methodological quality and heterogeneity of the extant literature constrained the derived conclusions. In addition, the literature commonly treated various subscales of QOL instruments as separate outcomes, increasing the probability of spurious findings. Conclusions. There is weak evidence that aspects of shared decision-making approaches are positively associated with QOL outcomes and very little evidence of a negative association. The extant literature largely assessed patient involvement, only capturing one aspect of the shared decision-making construct, and is of poor quality, necessitating robust studies examining the association.

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.

Neuro-cognitive impairment in breast cancer patients: pharmacological considerations

Post-chemotherapy cognitive impairment has been an issue of concern in cancer survivors. While most reviews are focused on patient-related factors, it is proposed that drug-related factors may also be determinants. The objective of this review is to study the relationship between the types and dose intensities of chemotherapy regimens on cognitive impairment in breast cancer patients through a systematic literature search. Eighteen prospective studies were selected. The types, dose intensities and durations of chemotherapy regimens received by subjects were compared against prevalence results obtained in individual studies. It was observed that the duration of impairment varied across different generations of chemotherapy regimens. Concurrent administration of multiple cytotoxic agents can lead to a synergistic decline on cognition. Current clinical evidence is insufficient to evaluate the relationship between the types, dose intensities of chemotherapy regimens and cognitive impairment. More investigation is needed to examine the role of pharmacological factors in chemotherapy-associated cognitive changes.

Instruments for estimation of health-related quality of life in patients with skull base neoplasms

With advances in treatment of patients with tumors of the skull base and associated improvement in length of survival, the need for assessment of quality of life (QOL) is becoming increasingly apparent. A thorough assessment of QOL, including functional, physical, social, and emotional status, as well as disease-specific symptoms, allows for comparison of treatments and informs treatment decisions. In addition, it allows for problems following intervention to be identified and addressed, thereby assisting patients in their pursuits of returning to their normal activities and level of functioning. Although health care providers and researchers are increasingly aware of the need to assess patients' QOL, few standardized measures exist with which to perform a comprehensive assessment of QOL in patients with skull base neoplasms. Further research is needed, including prospective trials using reliable and valid measures tapping various aspects of QOL and specific symptoms unique to patients with tumors of the skull base.

Long-term toxic effects of adjuvant chemotherapy in breast cancer

Breast cancer is the most common malignant tumor affecting women. Adjuvant systemic therapies have been shown to have a significant impact on reducing the risk for breast cancer recurrence and overall mortality. Chemotherapy remains an important and frequently used treatment option in the adjuvant setting, and the associated short-term adverse events are very well described. However, there is insufficient information regarding the long-term sequelae of most chemotherapeutic agents. In this review, we describe different potential long-term adverse events associated with adjuvant chemotherapy in breast cancer, with a particular focus on long-term cardiac toxicity, secondary leukemia, cognitive function, and neurotoxicity. In addition, we discuss the effect of adjuvant chemotherapy on fertility and sexual function of young breast cancer patients. These adverse events are frequently overshadowed by the well-demonstrated clinical efficacy and/or reassuring short-term safety profiles of the different chemotherapy regimens commonly used today. We believe that a proper understanding and appreciation of these adverse events will enable us to refine our strategies for managing breast cancer. The fact that adjuvant chemotherapy is often given to patients who might not really need it urges us to consider the whole spectrum of chemotherapy risks versus benefits to maximize benefit without compromising quality of life.

Predictors of distress and quality of life in patients undergoing cancer therapy: impact of treatment type and decisional role

PURPOSE

The purpose of this secondary investigation was to examine the impact of the type of treatment received and the perceived role in treatment decision making in predicting distress and cancer-specific quality of life in patients newly diagnosed with breast or prostate cancer.

METHOD

Participants included 1057 newly diagnosed breast and prostate cancer patients from four Canadian cancer centers who partook in a randomized controlled trial examining the utility of providing patients with an audio-recording of their treatment planning consultation. A MANCOVA was performed to predict distress and cancer-specific quality of life at 12 weeks post-consultation based on control variables (patient age, education, residence, tumor size (breast sample), gleason score (prostate sample), and receipt of an initial treatment consultation recording), predictor variables (treatment type--chemotherapy, hormone therapy, radiation therapy; decisional role--active, collaborative, passive), and interactions between these predictors.

RESULTS

Women who received chemotherapy and reported having played a more passive role in treatment decision making had significantly greater distress and lower cancer-specific quality of life at 12-week post-consultation. There were no statistically significant predictors of these outcomes identified for men with prostate cancer.

CONCLUSION

Receipt of chemotherapy places women with breast cancer at risk for distress and reduced quality of life, but only for the subset of women who report playing a passive role in treatment decision making. Prospective, longitudinal studies are needed to confirm the present findings and to explicate the antecedents, composition, and consequences of the 'passive' decisional role during the treatment phase of the cancer trajectory.

The effects of chemotherapy on Useful Field of View (UFOV) in younger and older breast cancer patients

Chemotherapy is thought to cause cognitive deficits in some breast cancer patients, but the relative effects on older and younger breast cancer patients are unknown. The effects of chemotherapy on everyday cognitive tasks have not been examined. Thirty-eight female breast cancer survivors (3 to 45 months post chemotherapy) were compared to 55 age-matched control participants. Participants completed the Useful Field of View (UFOV), a computerized test of visual information processing that has been shown to decline with age, and which has been used to predict older adults' driving performance. Older chemotherapy patients performed more poorly than controls on the UFOV speed of processing, but not on the other two components. They also performed more poorly than younger chemotherapy patients. On the divided attention and selective attention components of the UFOV, older participants performed more poorly than younger participants, but there were no significant differences between chemotherapy patients and controls. These findings are explained in terms of brain changes thought to be caused by chemotherapy, which might have the most impact on older adults, already at risk for behavioral slowing.

Renaming “Chemobrain”

A subset of breast cancer survivors are reporting cognitive impairment after cancer treatment, which has commonly been attributed to the receipt of chemotherapy and colloquially termed "chemobrain." For some, a fear of this side effect enters into their decision regarding therapy. Our review of the literature reveals that so-called "chemobrain" is complex and that factors other than chemotherapy may affect cognitive function, including the impact of surgery and anesthesia, hormonal therapy, menopause, anxiety, depression, fatigue, supportive care medications, genetic predisposition, comorbid medical conditions, or possibly paraneoplastic phenomenon. Studies to date have differed in their assessment and definition of cognitive impairment, thus, making comparisons between studies difficult. In addition, most studies have been limited by a small sample size, and there has been a general lack of focus on older patients despite their high concentration within the cancer population. Large, multicenter studies are needed to better understand the magnitude and mechanism of cognitive changes in cancer survivors and to assess the impact of cognitive changes on the patient's daily lives. We propose that the phenomenon commonly referred to as "chemobrain" would be more accurately labeled "cancer- or cancer-therapy-associated cognitive change."

Effects of chemotherapeutic agents 5-fluorouracil and methotrexate alone and combined in a mouse model of learning and memory

RATIONALE

The concern that adjuvant cancer chemotherapy agents cause cognitive impairment in a significant number of patients has been expressed by patients and healthcare providers, but clinical studies have yielded conflicting results to date.

OBJECTIVE

We directly tested two commonly used chemotherapeutic agents in a mouse model of learning and memory.

MATERIALS AND METHODS

In the present study, mice were conditioned to respond for a liquid reinforcer (Ensure solution) in the presence of an audible tone on day 1 as a measure of acquisition and were then required to perform the same response on day 2 as a measure of retrieval and retention. Methotrexate and 5-fluorouracil were administered prior to the day 1 session.

RESULTS

Methotrexate (1.0-32 mg/kg) alone failed to alter mean latency acquisition, retrieval, or reinforced response rates. Similar to scopolamine, a known amnesic in this assay, 5-fluorouracil (3-75 mg/kg) failed to alter response rates or acquisition latency on day 1 but significantly altered latency to retrieve a previously learned response on day 2. In combination, 3.2 mg/kg methotrexate plus 75 mg/kg 5-fluorouracil significantly increased day 1 and day 2 acquisition and retrieval latencies without altering response rates or motivation to respond as measured by progressive ratio responding.

CONCLUSION

Taken together, these data demonstrate that 5-fluorouracil causes increased latencies for retrieval of previously learned behavioral responses and that combination of chemotherapeutic agents may produce greater delays than either agent alone, including when neither agent alone does so.

Neuropsychological sequelae of non-central nervous system cancer and cancer therapy

Cancer patients report numerous adverse symptoms associated with their disease and treatment including cognitive dysfunction, fatigue, and affective distress. Cognitive dysfunction is ubiquitous in patients with primary central nervous system (CNS) cancer and recent evidence has documented similar deficits in patients with non-CNS cancer as well. Both the cancer itself and treatments including chemotherapy, biological response modifiers, and hormonal therapies have been demonstrated to adversely impact cognitive and neurobehavioral function. Neuroimaging and neurophysiological investigations have likewise revealed alterations in brain function that are helping to account for the nature of these cognitive disorders. Similarly, preclinical animal research is assisting to identify the pathophysiological mechanisms that underlie treatment-related neurotoxicities. The coalescence of multidisciplinary clinical and research efforts hold promise for the development of interventions that may offer neuroprotection in addition to currently available symptomatic therapies and cognitive rehabilitation techniques.

Cognitive function after chemotherapy in adults with solid tumours

BACKGROUND

Evidence is emerging that some cancer survivors suffer cognitive impairment after chemotherapy; the cause is unknown.

METHODS

Here we review studies evaluating cognitive impairment in adult cancer survivors and discuss methodological challenges associated with this research. We evaluate evidence for cognitive impairment in cancer patients, the incidence of self-reported impairment, and identify potential mechanisms and confounders.

RESULTS

Most studies of cognitive function are cross-sectional and report impairment in 15-45% of subjects. Longitudinal studies suggest that some impairment is present prior to receiving chemotherapy, and that this worsens in some patients. The aetiology is unknown. A larger number of subjects self-report changes in cognitive function after chemotherapy; this does not correlate with objective testing.

CONCLUSIONS

Cognitive impairment occurs in a subset of cancer survivors and is generally subtle. Most evidence suggests an association with chemotherapy although other factors associated with the diagnosis and treatment of cancer may contribute.

Potential Mechanisms for Chemotherapy-Induced Impairments in Cognitive Function

PURPOSE/OBJECTIVES

To review the domains of cognitive function and their corresponding neuroanatomic structures as well as present current evidence for neurotoxicity associated with specific chemotherapeutic agents and potential mechanisms for chemotherapy-induced cognitive impairments.

DATA SOURCES

Published research articles, review articles, and textbooks.

DATA SYNTHESIS

Chemotherapy does not appear to cross the blood-brain barrier when given in standard doses; however, many chemotherapy drugs have the potential to cause cognitive impairments through more than one mechanism. In addition, patient factors may be protective or place individuals at higher risk for cognitive impairments.

CONCLUSIONS

Although evidence of chemotherapy-induced impairments in cognitive function exists, no clinical studies have attempted to elucidate the mechanisms for chemotherapy-induced impairments in cognitive function. In addition, further studies are needed to determine predictive factors, potential biomarkers, and relevant assessment parameters.

IMPLICATIONS FOR NURSING

The ability to identify high-risk patients has important implications for practice in regard to informed consent, patient education about the effects of treatment, and preventive strategies.

DNA repair in neurons: so if they don't divide what's to repair?

Neuronal DNA repair remains one of the most exciting areas for investigation, particularly as a means to compare the DNA repair response in mitotic (cancer) vs. post-mitotic (neuronal) cells. In addition, the role of DNA repair in neuronal cell survival and response to aging and environmental insults is of particular interest. DNA damage caused by reactive oxygen species (ROS) such as generated by mitochondrial respiration includes altered bases, abasic sites, and single- and double-strand breaks which can be prevented by the DNA base excision repair (BER) pathway. Oxidative stress accumulates in the DNA of the human brain over time especially in the mitochondrial DNA (mtDNA) and is proposed to play a critical role in aging and in the pathogenesis of several neurological disorders including Parkinson's disease, ALS, and Alzheimer's diseases. Because DNA damage accumulates in the mtDNA more than nuclear DNA, there is increased interest in DNA repair pathways and the consequence of DNA damage in the mitochondria of neurons. The type of damage that is most likely to occur in neuronal cells is oxidative DNA damage which is primarily removed by the BER pathway. Following the notion that the bulk of neuronal DNA damage is acquired by oxidative DNA damage and ROS, the BER pathway is a likely area of focus for neuronal studies of DNA repair. BER variations in brain aging and pathology in various brain regions and tissues are presented. Therefore, the BER pathway is discussed in greater detail in this review than other repair pathways. Other repair pathways including direct reversal, nucleotide excision repair (NER), mismatch repair (MMR), homologous recombination and non-homologous end joining are also discussed. Finally, there is a growing interest in the role that DNA repair pathways play in the clinical arena as they relate to the neurotoxicity and neuropathy associated with cancer treatments. Among the numerous side effects of cancer treatments, major clinical effects include neurocognitive dysfunction and peripheral neuropathy. These symptoms occur frequently and have not been effectively studied at the cellular or molecular level. Studies of DNA repair may help our understanding of how those cells that are not dividing could succumb to neurotoxicity with the clinical manifestations discussed in the following article.

Self-reported cognitive problems in women receiving adjuvant therapy for breast cancer

Self-reported cognitive problems are common among women receiving adjuvant therapy for breast cancer but are unrelated to actual cognitive impairment. To date, no studies have objectively measured impairment and asked patients to speak about the type and extent of problems they encounter. We report interview data from 142 breast cancer patients receiving adjuvant therapy. We aimed to identify the types of problems and the extent to which they interfered with everyday life. We investigated the relationship between self-reported and objective cognitive impairment, quality of life and psychological distress. The majority of participants reported problems with their memory (71% overall at 6 months, 60% at 18 months) and concentration (64% and 42%, respectively). This was unrelated to objective cognitive decline; rather, it was associated with psychological distress and quality of life. For the vast majority, the problems reported were everyday slips and lapses. The neuropsychological measures routinely used may lack the sensitivity to detect these subtle changes experienced by this group. In addition, the effects of mood on cognition may be more important in everyday life than in the highly structured neuropsychological test situation. Future research should focus on developing cognitive assessments that tap everyday functioning.

A 3-year prospective study of the effects of adjuvant treatments on cognition in women with early stage breast cancer

The neuropsychological performance of 85 women with early stage breast cancer scheduled for chemotherapy, 43 women scheduled for endocrine therapy and/or radiotherapy and 49 healthy control subjects was assessed at baseline (T1), postchemotherapy (or 6 months) (T2) and at 18 months (T3). Repeated measures analysis found no significant interactions or main effect of group after controlling for age and intelligence. Using a calculation to examine performance at an individual level, reliable decline on multiple tasks was seen in 20% of chemotherapy patients, 26% of nonchemotherapy patients and 18% of controls at T2 (18%, 14 and 11%, respectively, at T3). Patients who had experienced a treatment-induced menopause were more likely to show reliable decline on multiple measures at T2 (OR=2.6, 95% confidence interval (CI) 0.823–8.266 P=0.086). Psychological distress, quality of life measures and self-reported cognitive failures did not impact on objective tests of cognitive function, but were significantly associated with each other. The results show that a few women experienced objective measurable change in their concentration and memory following standard adjuvant therapy, but the majority were either unaffected or even improve over time.

A meta-analysis of the neuropsychological effects of adjuvant chemotherapy treatment in women treated for breast cancer

Given the improvement in mortality rates associated with breast cancer, the importance of understanding the long-term neuropsychological consequences of chemotherapy is becoming increasingly vital. This study applies meta-analytic techniques to the scant literature on the relationship between contemporary adjuvant chemotherapy treatment for breast cancer and cognitive dysfunction as examined through neuropsychological indices. Seven studies (involving more than 300 participants) were selected from over 200 potential articles, based on three inclusion criteria: presence of breast cancer, administration of chemotherapy treatment, and use of neuropsychological tests. From these, nine treatment-control comparisons were used to generate 129 Hedge's d effect sizes across the cognitive domains of simple attention, working memory short- and long-term memory, speed of processing, language, spatial abilities, and motor function. Small to medium cumulative effect sizes, showing diminished cognitive function for chemotherapy treatment groups compared to control groups, were obtained for each of the eight cognitive domains. Overall, these results suggest that women who undergo adjuvant chemotherapy as treatment for breast cancer may experience subtle yet consequential cognitive decline.

Neuropsychological function in high-risk breast cancer survivors after stem-cell supported high-dose therapy versus standard-dose chemotherapy: evaluation of long-term treatment effects

BACKGROUND

Studies on cognitive functioning in breast cancer patients point out that a subset of women exhibit chemotherapy-related neuropsychological impairment. Thereby, high-dose therapy may elevate the risk of cognitive dysfunctions. The primary purpose of the study was to evaluate the impact of high-dose versus standard-dose chemotherapy on the late neuropsychological outcome in randomized assigned high-risk breast cancer survivors. Next to focusing prevalence, function specificity and extent of cognitive impairment, the question as to whether doses-dependent group differences occur was investigated.

PATIENTS AND METHODS

Twenty-four high-dose and 23 standard-dose patients 5 years, on average, after treatment underwent a comprehensive neuropsychological assessment. In addition, 29 early-stage breast cancer patients matched for age, education and time since treatment were recruited as a comparison group.

RESULTS

Global cognitive impairment was observed in 8% of high-dose versus 13% of standard-dose compared with 3% of early-stage breast cancer patients. Compared with normative data, all patient groups performed worse on one attention subtest measuring the simple reaction time (P < 0.001 in each case). By contrast, no significant between-group differences on the late neuropsychological outcome were found.

CONCLUSIONS

Five years after treatment, standard-dose patients were slightly, but not significantly, more impaired in cognitive performance than high-dose patients.

Short-term treatment-related symptoms and quality of life: results from an international randomized phase III study of cisplatin with or without raltitrexed in patients with malignant pleural mesothelioma: an EORTC Lung-Cancer Group and National Cancer Institute, Canada, Intergroup Study

PURPOSE

For malignant pleural mesothelioma (MPM) patients with a poor prognosis, maintaining health-related quality of life (HRQOL) is important. This article compares the impact on HRQOL of first-line treatment with cisplatin versus raltitrexed and cisplatin.

PATIENTS AND METHODS

Patients with histologically-proven unresectable MPM, not pretreated with chemotherapy were randomly assigned to receive cisplatin 80 mg/m2 intravenously on day 1, with or without preceding infusion of raltitrexed 3 mg/m2. HRQOL was assessed with the European Organisation for Research and Treatment of Cancer Core Quality of Life Questionnaire C30 (EORTC QLQ-C30) and EORTC Lung Cancer Module (QLQ-LC13) tools. Assessments were conducted at baseline, immediately before every treatment cycle, at the end of treatment, and every six weeks for 12 months.

RESULTS

Two hundred fifty patients were randomly assigned, 80% were male with a median age of 58 years, WHO performance status 0, 1, and 2, in 25%, 62%, and 13% of cases. The clinical results found raltitrexed and cisplatin to be superior to cisplatin with regard to overall survival (P = .048). The global HRQOL scale was comparable at baseline on both treatment arms (P = .848); at no point was any significant difference apparent on this end point. Both treatments led to an improvement, over time, in dyspnoea. This effect is an important clinically meaningful reduction from baseline in the cisplatin/raltitrexed arm. However, the majority of scales of the EORTC QLQ-C30 or LC13 showed stabilization of HRQOL with few clinically significant differences between the treatment arms.

CONCLUSION

This study provides important information about the HRQOL of chemotherapy-treated MPM patients.

Electrophysiological correlates of information processing in breast-cancer patients treated with adjuvant chemotherapy

Cognitive deficits are found in a number of breast-cancer patients who have undergone adjuvant (Cyclophosphamide, Methotrexate, and 5-Fluorouracil (CMF)) chemotherapy, but the underlying mechanisms are still unclear. The objective of this study is to investigate information processing in these patients with concurrent registration of brain activity. Twenty-six breast-cancer patients treated with adjuvant CMF chemotherapy and a control group of 23 stage I breast-cancer patients not treated with chemotherapy were examined. Mean time since treatment for the CMF patients was 5.1 years after the last CMF course, and for the control patients 3.6 years after termination of radiotherapy. An information processing task was administered with concurrent EEG registration. Reaction times and the amplitudes and latencies of an Event Related Potential component (P3) in different task conditions related to input, central, and output processing of information were studied. Significant differences in latency and amplitude of the P3 component were found between the treatment groups with an earlier and reduced P3 in the chemotherapy group. Patients treated with chemotherapy had longer reaction times (although not significantly different) than the control group on all task conditions. Our data provide further evidence for long-term neurocognitive problems in breast-cancer patients treated with adjuvant (CMF) chemotherapy and offer new information regarding abnormalities in brain functioning in these patients.

A metaanalysis of studies of the effects of cancer chemotherapy on various domains of cognitive function

BACKGROUND

Little is known about the effects of chemotherapy on cognitive function. The purposes of this metaanalysis were to estimate the effect sizes for the effect of chemotherapy on each domain of cognitive function and to differentiate effect sizes by each method of comparison of effects (i.e., normative data, control group, or baseline data).

METHODS

Sixteen studies that evaluated cognitive function in chemotherapy patients were included in the study. DSTAT metaanalysis software was used to calculate an effect size and confidence intervals for each neuropsychologic test. Tests were assigned to a specific cognitive domain, and an average effect size was determined for each domain.

RESULTS

Only one domain of cognitive function (i.e., visual memory) had significant chemotherapy-induced impairment across all comparison types. However, when the neuropsychologic test scores of chemotherapy patients were compared with normative data, significant effect sizes were found for four domains of cognitive function (i.e., executive function, information processing speed, verbal memory, visual memory). In addition, significant, albeit small, effect sizes were found for language and verbal memory when chemotherapy patients' test scores were compared with test scores of healthy matched controls. All significant averaged effect sizes were in the negative direction, indicating that mean scores on neuropsychologic tests for patients who had received chemotherapy were on average lower than comparison scores.

CONCLUSION

Data from this metaanalysis supported the hypothesis that chemotherapy can have a negative impact on cognitive function. However, most deficits in this study ranged from small to moderate and were nonsignificant.

The nature and severity of cognitive impairment associated with adjuvant chemotherapy in women with breast cancer: a meta-analysis of the current literature

OBJECTIVE

Several studies have identified that adjuvant chemotherapy for breast cancer is associated with cognitive impairment; however, the magnitude of this impairment is unclear. This study assessed the severity and nature of cognitive impairment associated with adjuvant chemotherapy by conducting a meta-analysis of the published literature to date.

METHOD

Six studies (five cross-sectional and one prospective) meeting the inclusion criteria provided a total of 208 breast cancer patients who had undergone adjuvant chemotherapy, 122 control participants and 122 effect sizes (Cohen's d) falling into six cognitive domains. First, the mean of all the effect sizes within each cognitive domain was calculated (separately for cross-sectional and prospective studies); second, a mean effect size was calculated for all of the effect sizes in each cross-sectional study; and third, regression analyses were conducted to determine any relationships between effect size for each study and four different variables.

RESULTS

For the cross-sectional studies, each of the cognitive domains assessed (besides attention) showed small to moderate effect sizes (-0.18 to -0.51). The effect sizes for each study were small to moderate (-0.07 to -0.50) and regression analysis detected a significant negative logarithmic relationship (R2 = .63) between study effect size and the time since last receiving chemotherapy. For the prospective study, effect sizes ranged from small to large (0.11-1.09) and indicated improvements in cognitive function from the beginning of chemotherapy treatment to 3 weeks and even 1 year following treatment.

CONCLUSION

This meta-analysis suggests that cognitive impairment occurs reliably in women who have undergone adjuvant chemotherapy for breast cancer but that the magnitude of this impairment depends on the type of design that was used (i.e., cross-sectional or prospective). Thus, more prospective studies are required before definite conclusions about the effects of adjuvant chemotherapy on cognition can be made.

New Insights Into Erythropoietin and Epoetin Alfa: Mechanisms of Action, Target Tissues, and Clinical Applications

Recombinant human erythropoietin (epoetin alfa) has proven beneficial for the treatment of various anemias. The mechanism of action of endogenous erythropoietin and the therapeutic use of epoetin alfa to stimulate red blood cell production and improve the quality of life in cancer patients are reviewed here. Epoetin alfa may also attenuate the cognitive dysfunction associated with cancer therapy. Interestingly, functional endogenous erythropoietin receptor signaling pathways have been demonstrated in numerous nonerythropoietic tissues. Of particular importance, epoetin alfa confers neurotrophic and neuroprotective effects in cultured neurons and in several animal models for neurologic disease. In one clinical trial, epoetin alfa appeared to limit functional and histologic damage in patients with stroke. Therefore, in cancer patients receiving chemotherapy, the beneficial effects of epoetin alfa could be mediated not only through enhanced erythrocyte production but also via direct effects on the nervous system. Further investigation into the nonerythropoietic effects of epoetin alfa could broaden its clinical utility for patients with cancer and also provide new therapies for various neurologic disorders.

Chemotherapy-related cognitive dysfunction in breast cancer

OBJECTIVES

To provide an overview of chemotherapy-related cognitive dysfunction in breast cancer survivors, focusing on its pathophysiology, risk factors, assessment, and management.

DATA SOURCES

Published biomedical literature.

CONCLUSION

Chemotherapy-related cognitive dysfunction in patients with breast cancer is multifactorial and possibly related to anemia or a direct effect of chemotherapy on brain function. Clinical observation and subjective reports are useful assessments. Therapies directed at alleviating or preventing cognitive deficits are being investigated.

IMPLICATIONS FOR NURSING PRACTICE

Oncology nurses are important in monitoring cognitive function in patients with breast cancer receiving chemotherapy. Nurses who are aware of the risks, assessment, and management of cognitive impairment are better able to discuss these issues with patients and caregivers.