The cognitive effects of chemotherapy in post-menopausal breast cancer patients: a controlled longitudinal study

Neuromarkers of fatigue and cognitive complaints following chemotherapy for breast cancer: a prospective fMRI investigation

The aim of this study is to use functional magnetic resonance imaging (fMRI) to prospectively examine pre-treatment predictors of post-treatment fatigue and cognitive dysfunction in women treated with adjuvant chemotherapy for breast cancer. Fatigue and cognitive dysfunction often co-occur in women treated for breast cancer. We hypothesized that pre-treatment factors, unrelated to chemotherapy per se, might increase vulnerability to post-treatment fatigue and cognitive dysfunction. Patients treated with (n = 28) or without chemotherapy (n = 37) and healthy controls (n = 32) were scanned coincident with pre- and one-month post-chemotherapy during a verbal working memory task (VWMT) and assessed for fatigue, worry, and cognitive dysfunction. fMRI activity measures in the frontoparietal executive network were used in multiple linear regression to predict post-treatment fatigue and cognitive function. The chemotherapy group reported greater pre-treatment fatigue than controls and showed compromised neural response, characterized by higher spatial variance in executive network activity, than the non-chemotherapy group. Also, the chemotherapy group reported greater post-treatment fatigue than the other groups. Linear regression indicated that pre-treatment spatial variance in executive network activation predicted post-treatment fatigue severity and cognitive complaints, while treatment group, age, hemoglobin, worry, and mean executive network activity levels did not predict these outcomes. Pre-treatment neural inefficiency (indexed by high spatial variance) in the executive network, which supports attention and working memory, was a better predictor of post-treatment cognitive and fatigue complaints than exposure to chemotherapy per se. This executive network compromise could be a pre-treatment neuromarker of risk, indicating patients most likely to benefit from early intervention for fatigue and cognitive dysfunction.

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.

[A meta-analysis of chemotherapy related cognitive impairment in patients with breast cancer]

PURPOSE

The purpose of this study was to evaluate the cognitive effects of chemotherapy in patients with breast cancer.

METHODS

Using several databases, prospective studies were collected up to August 2011. Of 2,106 publications identified, 12 met the inclusion criteria, and 8 studies were used to estimate the effect size of chemotherapy on cognitive impairment.

RESULTS

Twelve studies were done since 2005 and most of the research was performed in Europe or North America. Eight studies were used to generate effect size across the cognitive domains of attention/concentration, verbal and visual memory, executive function, visuospatial skill, language, and subjective cognitive function. Each of the cognitive domains showed small effect sizes (-0.02 ~ -0.26), indicating diminished cognitive function for the chemotherapy group compared with non-chemotherapy groups.

CONCLUSION

Finding suggests that breast cancer patients who undergo chemotherapy may experience mild cognitive decline. Further study is needed to generate knowledge and guideline for interventions to address chemotherapy related cognitive impairment in these patients.

Chemotherapy-induced prospective memory impairment in patients with breast cancer

OBJECTIVE

This study aimed to investigate the event-based prospective memory (EBPM) and time-based prospective memory (TBPM) in chemotherapy-induced cognitive impairment in patients with breast cancer.

METHODS

Forty patients with breast cancer who underwent adjuvant chemotherapy and 40 age-matched and education-matched healthy women were administered with a battery of neuropsychological tests including EBPM and TBPM tasks.

RESULTS

A significant difference between breast cancer patients and controls was found in the scores on the mini-mental state examination (t = -11.684, p < 0.01), verbal fluency test (t = -7.939, p < 0.01), and digit span (t = -2.538, p < 0.05). Compared with healthy controls, breast cancer patients exhibited a poorer performance on EBPM (t = -7.096, p < 0.01) but not on TBPM (t = -1.921, p > 0.05).

CONCLUSIONS

Our results suggest that breast cancer patients who had undergone adjuvant chemotherapy show deficits in EBPM but not in TBPM.

Tibetan sound meditation for cognitive dysfunction: results of a randomized controlled pilot trial

OBJECTIVE

Although chemotherapy-induced cognitive impairment is common among breast cancer patients, evidence for effective interventions addressing cognitive deficits is limited. This randomized controlled trial examined the feasibility and preliminary efficacy of a Tibetan Sound Meditation (TSM) program to improve cognitive function and quality of life in breast cancer patients.

METHODS

Forty-seven breast cancer patients (mean age 56.3 years), who were staged I-III at diagnosis, 6-60 months post-chemotherapy, and reported cognitive impairment at study entry were recruited. Participants were randomized to either two weekly TSM sessions for 6 weeks or a wait list control group. Neuropsychological assessments were completed at baseline and 1 month post-treatment. Self-report measures of cognitive function (Functional Assessment of Cancer Therapy (FACT)-Cog), quality of life (SF-36), depressive symptoms (Center for Epidemiologic Studies Depression Scale), sleep disturbance (Pittsburgh Sleep Quality Index), fatigue (Brief Fatigue Inventory), and spirituality (FACT-Sp) were completed at baseline, the end of treatment, and 1 month later.

RESULTS

Relative to the control group, women in the TSM group performed better on the verbal memory test (Rey Auditory Verbal Learning Test trial 1) (p = 0.06) and the short-term memory and processing speed task (Digit Symbol) (p = 0.09) and reported improved cognitive function (p = 0.06), cognitive abilities (p = 0.08), mental health (p = 0.04), and spirituality (p = 0.05) at the end of treatment but not 1 month later.

CONCLUSIONS

This randomized controlled trial revealed that TSM program appears to be a feasible and acceptable intervention and may be associated with short-term improvements in objective and subjective cognitive function as well as mental health and spirituality in breast cancer patients.

A pilot study of prospective memory functioning in early breast cancer survivors

AIMS

To evaluate prospective memory (PM) functioning in early breast cancer (BC) survivors and its association with fatigue and depression.

METHODS

The Memory for Intention Screening Test, the Center for Epidemiologic Studies Depression Scale and the Functional Assessment of Cancer Therapy-Fatigue subscale were administered to 80 patients and 80 aged-matched healthy controls.

RESULTS

Patients performed more poorly than controls on the memory test (p < 0.001) and had a higher rate of impairment (odds ratio = 5.5, p < 0.01). Fatigue mediated the relationship between Group membership and PM performance.

CONCLUSIONS

BC survivors exhibited a clear pattern of PM deficit and fatigue was a major contributor to this deficit. This suggests that a common mechanism may be involved in fatigue symptoms and memory disturbances experienced by patients. Further research is needed to evaluate the role of adjuvant therapy in PM deficits and to explore whether interventions targeted at improving fatigue may also improve memory functioning in BC survivors.

The effect of systemic chemotherapy on neurogenesis, plasticity and memory

Chemotherapy has been enormously successful in treating many forms of cancer and improving patient survival rates. With the increasing numbers of survivors, a number of cognitive side effects have become apparent. These have been called "chemobrain" or "chemofog" among patient groups, who describe the symptoms as a decline in memory, concentration and executive functions. Changes which, although subtle, can cause significant distress among patients and prevent a return to the quality of life experienced before treatment. This cognitive side effect of chemotherapy was not anticipated as it had been assumed that chemotherapy agents, administered systematically, could not cross the blood-brain barrier and that the brain was therefore protected from their action. It is now realised that low concentrations of many chemotherapy agents cross the blood-brain barrier and even those that are completely prevented from doing so, can induce the production of inflammatory cytokines in peripheral tissues which in turn can cross the blood-brain barrier and impact on the brain. A large number of patient studies have shown that cognitive decline is found in a proportion of patients treated with a variety of chemotherapy agents for different types of cancer. The deficits experienced by these patients can last for up to several years and have a deleterious effect on educational attainment and ability to return to work. Imaging studies of patients after systemic chemotherapy show that this treatment produces structural and functional changes in the brain some of which seem to persist even when the cognitive deficits have ceased. This suggests that, with time, brain plasticity may be able to compensate for the deleterious effects of chemotherapy treatment. A number of mechanisms have been suggested for the changes in brain structure and function found after chemotherapy. These include both central and peripheral inflammatory changes, demyelination of white matter tracts, a reduction in stem cell proliferation in both the hippocampal neurogenic region and by oligodendrocyte precursors as well as changes in hormonal or growth factor levels. A number of possible treatments have been suggested which range from pharmacological interventions to cognitive behavioural therapies. Some of these have only been tested in animal models while others have produced varying degrees of improvement in patient populations. Currently, there is no recognised treatment and a greater understanding of the causes of the cognitive decline experienced after chemotherapy will be key to finding ways of preventing or treating the effects of chemobrain.

Brain vulnerability to chemotherapy toxicities

Chemotherapy-induced cognitive changes have been an increasing concern among cancer survivors. By using adjuvant treatment for breast cancer as the prototype, this manuscript reviews research from neuropsychological, imaging, genetic, and animal model studies that have examined the clinical presentation and potential mechanisms for cognitive changes associated with exposure to chemotherapy. An impressive body of research supports the hypothesis that a subgroup of patients is vulnerable to post-treatment cognitive changes, although not exclusively related to chemotherapy. Further, imaging and animal model studies provide accumulating evidence of putative mechanisms for chemotherapy-induced cognitive change. Models of aging are also reviewed in support of the proposal that cognitive changes associated with cancer and cancer treatments can be viewed in the context of factors that affect the trajectory of normal aging.

Chemotherapy was not associated with cognitive decline in older adults with breast and colorectal cancer: findings from a prospective cohort study

OBJECTIVES

This study tested 2 hypotheses: (1) chemotherapy increases the rate of cognitive decline in breast and colorectal cancer patients beyond what is typical of normal aging and (2) chemotherapy results in systematic cognitive declines when compared with breast and colorectal cancer patients who did not receive chemotherapy.

SUBJECTS

Data came from personal interviews with a prospective cohort of patients with breast (n=141) or colorectal cancer (n=224) with incident disease drawn from the nationally representative Health and Retirement Study (1998-2006) with linked Medicare claims.

MEASURES

The 27-point modified Telephone Interview for Cognitive Status was used to assess cognitive functioning, focusing on memory and attention. We defined the smallest clinically significant change as 0.4 points per year.

RESULTS

We used Bayesian hierarchical linear models to test the hypotheses, adjusting for multiple possible confounders. Eighty-eight patients were treated with chemotherapy; 277 were not. The mean age at diagnosis was 75.5. Patients were followed for a median of 3.1 years after diagnosis, with a range of 0 to 8.3 years. We found no differences in the rates of cognitive decline before and after diagnosis for patients who received chemotherapy in adjusted models (P=0.86, one-sided 95% posterior intervals lower bound: 0.09 worse after chemotherapy), where patients served as their own controls. Moreover, the rate of cognitive decline after diagnosis did not differ between patients who had chemotherapy and those who did not (P=0.84, one-sided 95% posterior intervals lower bound: 0.11 worse for chemotherapy group in adjusted model).

CONCLUSIONS

There was no evidence of cognitive decline associated with chemotherapy in this sample of older adults with breast and colorectal cancer.

Cancer- and cancer treatment-associated cognitive change: an update on the state of the science

Cognitive changes associated with cancer and cancer treatments have become an increasing concern. Using breast cancer as the prototype, we reviewed the research from neuropsychological, imaging, genetic, and animal studies that have examined pre- and post-treatment cognitive change. An impressive body of research supports the contention that a subgroup of patients is vulnerable to post-treatment cognitive problems. We also propose that models of aging may be a useful conceptual framework for guiding research in this area and suggest that a useful perspective may be viewing cognitive change in patients with cancer within the context of factors that influence the trajectory of normal aging.

Chemotherapy-related cognitive dysfunction

Many cancer patients develop treatment-related cognitive dysfunction that affects their quality of life and can result in diminished functional independence. There is an emerging body of transdisciplinary research demonstrating that chemotherapeutic agents can produce neurobiological changes within the brain, which are associated with a constellation of cognitive changes that can result in decreased quality of life and functional independence. The increased incidence of cancer, coupled with longer survival times, has resulted in larger numbers of cancer survivors who are struggling with this neurotoxicity. This review summarizes the neuropsychological findings in patients with breast and brain cancer who receive systemic chemotherapy as well as the recent animal and imaging research elucidating the mechanisms by which these therapies impact brain structure, function, and consequent behavior.

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.

Neuropsychological performance in survivors of breast cancer more than 20 years after adjuvant chemotherapy

PURPOSE

Adjuvant chemotherapy for breast cancer can have adverse effects on cognition shortly after administration. Whether chemotherapy has any long-term effects on cognition is largely unknown, yet it becomes increasingly relevant because of the widespread use of chemotherapy for early-stage breast cancer and the improved survival. We investigated whether cyclophosphamide, methotrexate, and fluorouracil (CMF) chemotherapy for breast cancer is associated with worse cognitive performance more than 20 years after treatment.

PATIENTS AND METHODS

This case-cohort study compared the cognitive performance of patients with breast cancer who had a history of adjuvant CMF chemotherapy treatment (six cycles; average time since treatment, 21 years; n = 196) to that of a population-based sample of women never diagnosed with cancer (n = 1,509). Participants were between 50 and 80 years of age. Exclusion criteria were ever use of adjuvant endocrine therapy, secondary malignancy, recurrence, and/or metastasis.

RESULTS

The women exposed to chemotherapy performed significantly worse than the reference group on cognitive tests of immediate (P = .015) and delayed verbal memory (P = .002), processing speed (P < .001), executive functioning (P = .013), and psychomotor speed (P = .001). They experienced fewer symptoms of depression (P < .001), yet had significantly more memory complaints on two of three measures that could not be explained by cognitive test performance.

CONCLUSION

Survivors of breast cancer treated with adjuvant CMF chemotherapy more than 20 years ago perform worse, on average, than random population controls on neuropsychological tests. The pattern of cognitive problems is largely similar to that observed in patients shortly after cessation of chemotherapy. This study suggests that cognitive deficits following breast cancer diagnosis and subsequent CMF chemotherapy can be long lasting.

Factors associated with long-term functional outcomes and psychological sequelae in women after breast cancer

The objective of this study was to examine factors impacting long-term functional outcomes and psychological sequelae in survivors of breast cancer (BC). A clinical assessment and structured interview assessed the impact of BC on participants' (n=85) current activity and restriction in participation, using validated questionnaires: Functional Independence Measure (FIM), Perceived Impact Problem Profile (PIPP) and Depression Anxiety Stress Scale (DASS). Participants showed good functional recovery (median motor FIM score=78). Three-quarters (74%) reported pain, 32% reported upper limb weakness, 31% pain limiting shoulder movement and 29% lymphoedema. One third (32%) reported greatest impact on psychological wellbeing. A substantial number of participants reported high levels of depression (22%), anxiety and stress (19% each). Factors associated with poorer current level of functioning and wellbeing included: younger participants, recent diagnoses, aggressive tumour types, receiving chemotherapy, shoulder limitation due to pain, and lymphoedema. BC survivors require long-term management of psychological sequelae impacting activity and participation.

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.

Changes in perceived attentional function in women following breast cancer surgery

After treatment for breast cancer, many women experience cognitive problems, as determined by objective neuropsychological tests. However, the ecological validity of these tests has been questioned. This study explored the trajectory of perceived attentional function from before to 24 months after surgery in women with breast cancer and examined the effect of adjuvant treatment on this perceived attentional function. Women with breast cancer (N = 200) were assessed for perceived cognitive function by measuring attentional function using the attentional function index (AFI). Covariates included anxiety, depression, fatigue, and sleep disturbance. Perceived attentional function declined in 54% of women at 1 month after surgery. At 1 and 2 years after surgery, 41 and 30% of women, respectively, still perceived this decline. The mean AFI decreased to the lowest point 1 month after surgery, but improved gradually afterward, taking about 1 year to return to the pre-surgery level. Decreases in perceived attentional function were associated with increases in anxiety, depression, fatigue, and sleep disturbance. After controlling for baseline differences and covariates, mean AFI scores were not associated with adjuvant treatment. Perceived cognitive function deteriorated after surgery but improved over time. It was not associated with adjuvant cancer treatment.

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.

A prospective longitudinal study of chemotherapy-induced cognitive changes in breast cancer patients

PURPOSE

Evidence for chemotherapy-induced cognitive impairment remains inconclusive. This study was designed to determine the trajectory of cognitive function over time in women with breast cancer, who received doxorubicin and cyclophosphamide (AC) alone or followed by a taxane. Associations between changes in cognitive function and potential covariates including anxiety, depression, fatigue, hemoglobin level, menopausal status, and perception of cognitive function were evaluated.

METHODS

The Repeatable Battery for the Assessment of Neuropsychological Status, Stroop Test, and Grooved Pegboard were used to assess cognitive function in a group of 71 women prior to chemotherapy, a week after completing the last cycle of AC, as well as 1 week and 6 months after the completion of all chemotherapy.

RESULTS

Cognitive impairment was found in 23% of women prior to chemotherapy. Hierarchical linear modeling showed significant decreases after receiving chemotherapy followed by improvements 6 months after the completion of chemotherapy in the cognitive domains of visuospatial skill (p < 0.001), attention (p = 0.022), delayed memory (p = 0.006), and motor function (p = 0.043). In contrast, immediate memory, language, and executive function scores did not change over time.

CONCLUSION

These results suggest that having a breast cancer diagnosis may be associated with cognitive impairment. While chemotherapy may have a negative impact on cognitive function, chemotherapy-related impairments appear to be more acute than chronic side effects of therapy. Further studies are needed to provide insight into the clinical significance and potential mechanisms of cancer and treatment-related cognitive impairments.