Cognitive effects of chemotherapy in post-menopausal breast cancer patients 1 year after treatment

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).

Designing conceptual model-based research in chemotherapy-related changes in cognitive function

Any well-designed biobehavioral research will begin with a comprehensive understanding and stated conceptual approach to the issue to be studied and the hypotheses to be tested. Following this conceptual orientation, the research protocol can be designed. This chapter reviews these factors to guide conceptual model-based research of chemotherapy-related changes in cognitive function.

Is systemic anti-cancer therapy neurotoxic? Does chemo brain exist? And should we rename it?

The existence of chemo brain has become almost universally accepted, although many details of the concept are controversial. Data about the different types of cognitive impairment and their duration are not always consistent in the literature. We still do not know which cytotoxic agents are responsible, which characteristics make patients vulnerableand which biologic mechanisms are involved. This chapter reviews the recent literature and provides an actualized definition of chemo brain, including recent functional imaging data and discusses its controversial aspects. Potential underlying mechanisms and their future possible clinical applications in the prevention and treatment of chemo brain are also discussed. These issues are of clinical importance given the prevalence of breast carcinoma, the increased use of chemotherapy as adjuvant therapy, the increasing use of more aggressive dosing schedules and the increasing survival rates. Better-designed future trials should lead to a better definition and understanding of chemo brain and to future therapies.

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.

Gray matter reduction associated with systemic chemotherapy for breast cancer: a prospective MRI study

Brain gray matter alterations have been reported in cross-sectional magnetic resonance imaging (MRI) studies of breast cancer patients after cancer treatment. Here we report the first prospective MRI study of women undergoing treatment for breast cancer, with or without chemotherapy, as well as healthy controls. We hypothesized that chemotherapy-associated changes in gray matter density would be detectable 1 month after treatment, with partial recovery 1 year later. Participants included breast cancer patients treated with (CTx+, N = 17) or without (CTx-, N = 12) chemotherapy and matched healthy controls (N = 18). MRI scans were acquired at baseline (after surgery but before radiation, chemotherapy, and/or anti-estrogen treatment), 1 month after completion of chemotherapy (M1), and 1 year later (Y1). Voxel-based morphometry (VBM) was used to evaluate gray matter density differences between groups and over time. There were no between-group gray matter differences at baseline. Group-by-time interactions showed declines from baseline to M1 in both cancer groups relative to controls. Within-group analyses indicated that at M1 relative to baseline the CTx+ group had decreased gray matter density in bilateral frontal, temporal, and cerebellar regions and right thalamus. Recovery was seen at Y1 in some regions, although persistent decreases were also apparent. No significant within-group changes were found in the CTx- or control groups. Findings were not attributable to recency of cancer surgery, disease stage, psychiatric symptoms, psychotropic medication use, or hormonal treatment status. This study is the first to use a prospective, longitudinal approach to document decreased brain gray matter density shortly after breast cancer chemotherapy and its course of recovery over time. These gray matter alterations appear primarily related to the effects of chemotherapy, rather than solely reflecting host factors, the cancer disease process, or effects of other cancer treatments.

Effects of 5-FU

5-fluorouracil (5-FU) is a chemotherapeutical agent used to treat cancers including breast and colorectal. Working as an antimetabolite to prevent cell proliferation, it primarily inhibits the enzyme thymidylate synthase blocking the thymidine formation required for DNA synthesis. Although having a relatively short half-life (< 30 mins) it readily enters the brain by passive diffusion. Clinically, it is used both as a single agent or in combination with other chemotherapies and has been associated with the long-term side effects of cognitive impairment, known as "chemo brain" or "chemo fog" These accounts have come primarily from patients undergoing treatment for breast cancer who report symptoms including confusion and memory impairment, which can last for months to years. Psychometric studies of patients have suffered from confounding variables, which has led to the use of rodent models to assess the cognitive effects of this drug. Researchers have used behavioral and physiological tests including the Morris water maze, novel object location/recognition tests, shock motivated T-maze, sensory gating and conditioning, to investigate the effect of this drug on cognition. The variety of cognitive tests and the difference in dosing and administration of 5-FU has led to varied results, possibly due to the different brain regions associated with each test and the subtlety of the drug's effect, but overall these studies indicates that 5-FU has a negative effect on memory, executive function and sensory gating. 5-FU has also been demonstrated to have biochemical and structural changes on specific regions of the brain. Evidence shows it can induce apoptosis and depress cell proliferation in the neurogenic regions of the adult brain including the sub granular zone (SGZ) within the hippocampus and in oligodendrocyte precursor populations within white matter tracts. Furthermore, investigations indicate levels ofdoublecortin, a marker for newly formed neurons and brain derived neurotrophic factor, a cell survival modulator, are also reduced by 5-FU in the SGZ. Thus, 5-FU appears to have a lasting negative impact on cognition and to affect cellular and biochemical markers in various brain regions. Further work is needed to understand the exact mechanisms involved and to devise strategies for the prevention or recovery from these symptoms.

Predictors of cognitive decline after chemotherapy in breast cancer patients

The objective of this study is to identify whether decline in cognitive functioning after chemotherapy in women with breast cancer is associated with health/disease, treatment, and psychological variables. Neuropsychological performance, health/disease, and treatment-related information of 136 women with breast cancer (age M = 49.38; SD = 7.92; range = 25.25-67.92) was assessed pre-chemotherapy and 1-month post-chemotherapy. The Reliable Change Index corrected for practice (RCIp) identified women whose performance significantly declined, while Pearson correlations assessed the relationship between cognitive change and predictor variables. A total of 16.9% of women showed significant decline post-chemotherapy, with affected domains including verbal learning and memory, abstract reasoning, and motor coordination. Decline in hemoglobin levels and increased anxiety over the course of chemotherapy was found to significantly predict impairment in multiple cognitive measures. Change in specific cognitive measures was significantly associated with baseline fatigue, depression, and functional well-being (r = 0.23 to 0.33; p = .01 to < .001). Although the effects are small, there is evidence that psychological and health factors may increase vulnerability to cognitive dysfunction after chemotherapy for breast cancer. Significant associations reported in this study may be useful in the identification and treatment of at-risk individuals.

Regional brain activation during verbal declarative memory in metastatic breast cancer

PURPOSE

To determine the neurofunctional basis of verbal memory dysfunction in women with metastatic breast cancer. This objective was based on previous research suggesting memory and other cognitive deficits in this population. We attempted to determine if verbal memory impairments were related to the most commonly studied disease parameters including adjuvant chemotherapy and chronic stress-related disruption of limbic system structures.

EXPERIMENTAL DESIGN

We used functional magnetic resonance imaging to test our hypothesis that women with breast cancer would show significantly lower brain activation during verbal declarative memory tasks compared with age and education-matched healthy female controls. We also assessed several stress-related variables including diurnal cortisol levels to test our hypothesis that women with breast cancer would show higher stress and this would contribute to brain activation deficits during memory tasks.

RESULTS

Women with breast cancer had significantly lower prefrontal cortex activation during the memory encoding condition compared with controls. However, the breast cancer group showed significantly greater activation than controls during the recall condition in multiple, diffuse brain regions. There were no significant differences between the groups in stress-related variables. Women who were treated with cyclophosphamide, methotrexate, and 5-fluorouracil chemotherapy showed lower prefrontal cortex activation during memory encoding.

CONCLUSIONS

These results suggest that women with metastatic breast cancer may be at risk for verbal memory impairments as a result of altered functional brain activation profiles. These findings may be associated with chemotherapy type and/or other aspects of the breast cancer disease process.