Decline in Cognitive Function in Older Adults With Early-Stage Breast Cancer After Adjuvant Treatment

Cancer-related cognitive impairment: an update on state of the art, detection, and management strategies in cancer survivors

BACKGROUND

Advances in diagnostic and therapeutic strategies in oncology have significantly increased the chance of survival of cancer patients, even those with metastatic disease. However, cancer-related cognitive impairment (CRCI) is frequently reported in patients treated for non-central nervous system cancers, particularly during and after chemotherapy.

DESIGN

This review provides an update of the state of the art based on PubMed searches between 2012 and March 2019 on 'cognition', 'cancer', 'antineoplastic agents' or 'chemotherapy'. It includes the most recent clinical, imaging and pre-clinical data and reports management strategies of CRCI.

RESULTS

Evidence obtained primarily from studies on breast cancer patients highlight memory, processing speed, attention and executive functions as the most cognitive domains impaired post-chemotherapy. Recent investigations established that other cancer treatments, such as hormone therapies and targeted therapies, can also induce cognitive deficits. Knowledge regarding predisposing factors, biological markers or brain functions associated with CRCI has improved. Factors such as age and genetic polymorphisms of apolipoprotein E, catechol-O-methyltransferase and BDNF may predispose individuals to a higher risk of cognitive impairment. Poor performance on neuropsychological tests were associated with volume reduction in grey matter, less connectivity and activation after chemotherapy. In animals, hippocampus-based memory and executive functions, mediated by the frontal lobes, were shown to be particularly susceptible to the effects of chemotherapy. It involves altered neurogenesis, mitochondrial dysfunction or brain cytokine response. An important next step is to identify strategies for managing cognitive difficulties, with primary studies to assess cognitive training and physical exercise regimens.

CONCLUSIONS

CRCI is not limited to chemotherapy. A multidisciplinary approach has improved our knowledge of the complex mechanisms involved. Nowadays, studies evaluating cognitive rehabilitation programmes are encouraged to help patients cope with cognitive difficulties and improve quality of life during and after cancer.

Doxorubicin and cisplatin induced cognitive impairment: The possible mechanisms and interventions

Chemotherapy has significantly increased the number of cancer survivors. However, chemotherapy itself carries various adverse effects that limit the efficacy of treatment and quality of life of the cancer patients. Most patients who have received chemotherapy report some cognitive deficit characterized by dysfunction in memory, learning, concentration, and reasoning. The phenomenon of cognitive decline developed from chemotherapy treatment is referred to as chemotherapy-induced cognitive impairment (CICI) or chemobrain. The two most common cancers occurring worldwide are lung and breast cancer. The predominant chemotherapeutic drugs used to treat lung and breast cancer are doxorubicin and cisplatin. There is evidence to suggest that both drugs potentially induce chemobrain. The evidence around the proposed pathogenesis of chemobrain caused by these two drugs is inconsistent. Understanding the underlying mechanisms involved in the development of chemobrain would aid in the prevention or treatment of the adverse effects of chemotherapy on brain. This review will summarize and discuss controversial findings and possible mechanisms involved in the development of chemobrain and the interventions which could limit it from in vitro, in vivo, and clinical studies.

Roles of biological and psychosocial factors in experiencing a psychoneurological symptom cluster in cancer patients

PURPOSE

(a) To identify subgroups with unique psychoneurological symptom-cluster experience (depression, cognitive impairment, fatigue, sleep disturbance, and pain) and (b) to examine whether the selected demographic, clinical, psychological, and biological factors determine a symptom-cluster experience in cancer patients.

METHOD

The sample included 203 patients with diverse cancer types recruited from a Korean university hospital. Latent profile analyses were conducted to identify subgroups. Influencing factors of subgroup membership (demographic/clinical variables, hemoglobin level, social support, and psychological stress) were included as covariates in latent profile analysis and analyzed by multinomial logistic regression.

RESULTS

Latent profile analyses classified patients into two subgroups with a unique symptom cluster experience: patients experiencing high intensity in all symptoms within the cluster (the all-high-symptom subgroup, 71%) and patients experiencing low intensity in all symptoms within the cluster (all-low-symptom subgroup, 29%). The validity of the two subgroups was confirmed by the group classification accuracy (97% of the all-low-symptom subgroup and 99% of the all-high-symptom subgroup) and by significant Wald's mean equality tests, showing each symptom (depression, cognitive impairment, fatigue, sleep disturbance, and pain) significantly differentiated the two subgroups (ps < .001). Psychological stress independently determined the subgroup membership. Patients with high levels of stress were more likely to be in the all-high-symptom group (OR = 4.69, p < .0001). Hemoglobin level, cancer diagnosis, social support, and previous chemotherapy experience did not influence group membership.

CONCLUSIONS

A large number of patients experience five psychoneurological symptoms simultaneously due to psychological stress. Interventions targeted to stress would be beneficial for those patients.

Co-occuring symptoms in older oncology patients with distinct attentional function profiles

PURPOSE

Evaluate how subgroups of older adults with distinct attentional function profiles differ on the severity of nine common symptoms and determine demographic and clinical characteristics and symptom severity scores associated with membership in the low and moderate attentional function classes.

METHODS

Three subgroups of older oncology outpatients were identified using latent profile analysis based on Attentional Function Index (AFI) scores. Symptoms were assessed prior to the second or third cycle of CTX. Logistic regressions evaluated for associations with attentional function class membership.

RESULTS

For trait anxiety, state anxiety, depression, sleep disturbance, morning fatigue, and evening fatigue scores, differences among the latent classes followed the same pattern (low > moderate > high). For morning and evening energy, compared to high class, patients in low and moderate classes reported lower scores. For pain, compared to moderate class, patients in low class reported higher scores. In the logistic regression analysis, compared to high class, patients with lower income, higher comorbidity, higher CTX toxicity score, and higher levels of state anxiety, depression, and sleep disturbance were more likely to be in low AFI class. Compared to high class, patients with higher comorbidity and trait anxiety and lower morning energy were more likely to be in moderate AFI class.

CONCLUSIONS

Consistent with the hypothesis that an increased risk for persistent cognitive decline is likely related to a variety of physical and psychological factors, for six of the nine symptoms, a "dose response" effect was observed with higher symptom severity scores associated with a progressive decline in attentional function.

Cognitive complaints in cancer survivors and expectations for support: Results from a web-based survey

Background

Cognitive complaints are common in cancer survivors. We aimed to assess cognitive complaints in cancer survivors and the associated factors using a large web–based survey.

Methods

This online survey was proposed to cancer survivors. Participants completed several questions on cognitive complaints experience, expectations for support of cognitive difficulties, preexisting knowledge about chemotherapy–associated cognitive problems and demographic and medical variables. We used multivariable logistic regression models to estimate Odds Ratios and 95% confidence intervals to estimate associations.

Results

Among 1610 eligible participants (median age 52 [21‐84]), >85% (n = 1393) were breast cancer survivors. Median postcancer treatment time (excluding hormone therapy) was 2.83 years [0.8‐33]. Seventy five percent of the participants (n = 1214) reported cognitive complaints related to cancer treatments. Cognitive difficulties had an impact on work resumption for 76% of the participants (n = 754/982). Most cancer survivors would like to receive support (75%, n = 909) and especially cognitive training (72%, n = 658). Chemotherapy was strongly associated with cognitive complaints (multivariable OR = 3.67, 95% CI: 2.80‐4.82). Self–reported sleep difficulties (OR_{often vs. never} = 2.84, 95% CI: 1.80‐4.47), preexisting knowledge about chemotherapy–associated cognitive problems (OR_{No vs. Yes} = 1.69, 95% CI: 1‐29‐2.22) and age (OR_{21‐64 vs. ≥65} = 0.37, 95% CI: 0.23‐0.58) were also associated with cancer–related cognitive complaints.

Conclusions

According to this large web–based survey including mainly breast cancer survivors, cognitive complaints were reported by three quarters of participants, which reinforces that cognitive difficulties are a major issue in cancer survivors. Chemotherapy, self–reported sleep difficulties and preexisting knowledge about chemotherapy–associated cognitive problems were strongly associated with cancer–related cognitive complaints. Most cancer survivors wished to receive support and especially cognitive training.

Impact of anxio-depressive symptoms and cognitive function on oral anticancer therapies adherence

PURPOSE

Oral anticancer therapies have an important place in the therapeutic arsenal, but factors influencing adherence to oral treatment are poorly documented in oncology. The objective of this study was to assess the impact of anxio-depressive symptoms and cognitive functioning on oral medication adherence.

METHODS

This prospective study included cancer patients initiating a first oral therapy. Before initiation of treatment, an assessment of depression, anxiety, and cognition was performed. Using self-report questionnaires, we collected information on socio-demographic conditions and the non-adherence at 1 (M1) and 3 months (M3) after the beginning of treatment.

RESULTS

Among 129 patients enrolled, median age was 70 years and 81% of patients were treated for metastatic cancer. Before initiating treatment, 16% and 8% of patients presented respectively depression and anxiety symptoms. Global cognitive impairment was observed in 51% of patients. Ten percent of the patients were non-adherent at M1 and 13% at M3. Depression was strongly associated with non-adherence at M1 (P = 0.046) and M3 (P = 0.014), but not anxiety. Non-adherence was associated with lower working memory (P = 0.037) and digit memory (P = 0.018) at M1 and short-term memory (P = 0.04) at M3. Patients with more than eight co-medications were more often non-adherents (P = 0.055).

CONCLUSIONS

Non-adherence to oral anticancer therapies was mainly associated to depression. Focusing on depressive symptoms before initiation of oral anticancer therapy could help to identify patient profiles more likely to fail self-management. Working memory, digit memory, and short-term memory also seem to play a role in non-adherence. Further studies should include a more specific population, especially according to age.

Interdisciplinary Screening, Diagnosis, Therapy and Follow-up of Breast Cancer. Guideline of the DGGG and the DKG (S3-Level, AWMF Registry Number 032/045OL, December 2017) - Part 2 with Recommendations for the Therapy of Primary, Recurrent and Advanced Breast Cancer

Purpose The aim of this official guideline coordinated and published by the German Society for Gynecology and Obstetrics (DGGG) and the German Cancer Society (DKG) was to optimize the screening, diagnosis, therapy and follow-up care of breast cancer. Method The process of updating the S3 guideline published in 2012 was based on the adaptation of identified source guidelines. They were combined with reviews of evidence compiled using PICO (Patients/Interventions/Control/Outcome) questions and with the results of a systematic search of literature databases followed by the selection and evaluation of the identified literature. The interdisciplinary working groups took the identified materials as their starting point and used them to develop suggestions for recommendations and statements, which were then modified and graded in a structured consensus process procedure. Recommendations Part 2 of this short version of the guideline presents recommendations for the therapy of primary, recurrent and metastatic breast cancer. Loco-regional therapies are de-escalated in the current guideline. In addition to reducing the safety margins for surgical procedures, the guideline also recommends reducing the radicality of axillary surgery. The choice and extent of systemic therapy depends on the respective tumor biology. New substances are becoming available, particularly to treat metastatic breast cancer.

Cancer-Related Cognitive Outcomes Among Older Breast Cancer Survivors in the Thinking and Living With Cancer Study

PURPOSE

To determine treatment and aging-related effects on longitudinal cognitive function in older breast cancer survivors.

METHODS

Newly diagnosed nonmetastatic breast cancer survivors (n = 344) and matched controls without cancer (n = 347) 60 years of age and older without dementia or neurologic disease were recruited between August 2010 and December 2015. Data collection occurred during presystemic treatment/control enrollment and at 12 and 24 months through biospecimens; surveys; self-reported Functional Assessment of Cancer Therapy-Cognitive Function; and neuropsychological tests that measured attention, processing speed, and executive function (APE) and learning and memory (LM). Linear mixed-effects models tested two-way interactions of treatment group (control, chemotherapy with or without hormonal therapy, and hormonal therapy) and time and explored three-way interactions of ApoE (ε4+ v not) by group by time; covariates included baseline age, frailty, race, and cognitive reserve.

RESULTS

Survivors and controls were 60 to 98 years of age, were well educated, and had similar baseline cognitive scores. Treatment was related to longitudinal cognition scores, with survivors who received chemotherapy having increasingly worse APE scores ( P = .05) and those initiating hormonal therapy having lower LM scores at 12 months ( P = .03) than other groups. These group-by-time differences varied by ApoE genotype, where only ε4+ survivors receiving hormone therapy had short-term decreases in adjusted LM scores (three-way interaction P = .03). For APE, the three-way interaction was not significant ( P = .14), but scores were significantly lower for ε4+ survivors exposed to chemotherapy (-0.40; 95% CI, -0.79 to -0.01) at 24 months than ε4+ controls (0.01; 95% CI, 0.16 to 0.18; P < .05). Increasing age was associated with lower baseline scores on all cognitive measures ( P < .001); frailty was associated with baseline APE and self-reported decline ( P < .001).

CONCLUSION

Breast cancer systemic treatment and aging-related phenotypes and genotypes are associated with longitudinal decreases in cognitive function scores in older survivors. These data could inform treatment decision making and survivorship care planning.

Distinct attentional function profiles in older adults receiving cancer chemotherapy

PURPOSE

While attentional function is an extremely important patient outcome for older adults, research on changes in function in this group is extremely limited. The purposes of this study were to: identify subgroups of older patients (i.e., latent growth classes) based on changes in their level of self-reported attentional function; determine which demographic and clinical characteristics were associated with subgroup membership; and determine if these subgroups differed on quality of life (QOL) outcomes.

METHODS

Older oncology outpatients (n = 365) who were assessed for changes in attention and working memory using the Attentional Function Index a total of six times over two cycles of chemotherapy (CTX). QOL was assessed using the Medical Outcomes Study-Short Form 12 and the QOL-Patient Version Scale. Latent profile analysis (LPA) was used to identify subgroups of older adults with distinct attentional function profiles.

RESULTS

Three distinct attentional functional profiles were identified (i.e., low, moderate, and high attentional function). Compared to the high class, older adults in the low and moderate attentional function classes had lower functional status scores, a worse comorbidity profile and were more likely to be diagnosed with depression. In addition, QOL scores followed an expected pattern (low class < moderate class < high attentional function class).

CONCLUSIONS

Three distinct attentional function profiles were identified among a relatively large sample of older adults undergoing CTX. The phenotypic characteristics associated with membership in the low and moderate latent classes can be used by clinicians to identify high risk patients.

How to Identify and Manage Cognitive Dysfunction After Breast Cancer Treatment

Attention and memory dysfunction is a common complaint among patients with breast cancer that can be reported during and up to several years after treatment. It can negatively affect patients' quality of life and their ability to work. This phenomenon has mainly been studied in patients with breast cancer who are treated with adjuvant chemotherapy. Women describe concentration problems and difficulties with word finding, multitasking, or remembering new information, as well as more effort and time needed to accomplish these tasks. Such cognitive dysfunction is subtle or moderate and occurs in 15% to 25% of patients. Older patients seem more likely to experience cognitive decline with chemotherapy than do young women with breast cancer. Patients who report that cognitive dysfunction has affected their daily lives for 6 to 12 months after the end of chemotherapy or during hormone therapy may need referral to a neuropsychologist. During the cognitive assessment, the etiology of their cognitive complaints is sought and neuropsychological tests are administered to assess objective cognitive functioning. Psychological factors-fatigue and pain-should be assessed systematically with cognitive complaints to identify precisely the cause of the problems. A nonpharmacologic approach-mainly cognitive rehabilitation-seems to be the most promising for the management of these difficulties, but these preliminary results require confirmation. In the future, early detection of cognitive impairment and cognitive rehabilitation should be included in the portfolio of oncology supportive care to facilitate the return to work of young women and to avoid potential repercussions on adherence to oral treatments and on autonomy in older patients.

Cognitive Changes After Adjuvant Treatment in Older Adults with Early-Stage Breast Cancer

BACKGROUND

Group-based trajectory modeling is particularly important to identify subgroups of patients with pathological cognitive changes after cancer treatment. To date, only one study has explored cognitive trajectories in older patients with cancer. The present article describes objective cognitive changes before to after adjuvant treatment in older adults with early-stage breast cancer (EBC) after adjuvant treatment compared with healthy controls.

PATIENTS AND METHODS

Participants were patients ≥65 years of age with newly diagnosed EBC and healthy controls (age-, sex-, and education-matched). The pretreatment assessment was conducted before adjuvant therapy, and the post-treatment assessment after the end of the first adjuvant treatment. Objective cognitive changes before to after treatment were evaluated based on the Reliable Change Index for cognitive decline accounting for cognitive impairment status.

RESULTS

The sample consisted of women newly diagnosed with EBC (n = 118) and healthy controls (n = 62). Five patterns of changes before to after treatment were identified based on the presence of cognitive decline and cognitive impairment. The distribution of these five change patterns was statistically significant (p = .0001). Thirty-six percent of patients had phase shift changes, 31% without initial objective cognitive impairment developed impairment, 15% had a normal aging, 12% had a nonpathological decline, and 6% experienced accelerated cognitive decline.

CONCLUSION

This study described for the first time objective cognitive changes before to after treatment of older adults with EBC immediately after the end of adjuvant treatment. A longer-term remote follow-up of adjuvant treatment is needed to better understand the cognitive trajectories of older patients with EBC.

IMPLICATIONS FOR PRACTICE

After the end of adjuvant treatment, 31% of older adults with early-stage breast cancer without initial objective cognitive impairment developed impairment, and 6% experienced accelerated cognitive decline. Initial cognitive functioning should be included in the balance of benefits and harms of systemic therapy for patients who are likely to be at highest risk for cognitive decline after cancer treatments. Regular cognitive follow-up of patients who had cognitive impairment before cancer treatment should monitor symptoms suggestive of neurodegenerative disease and avert the effect of cognitive disorders on patients' autonomy.

Chemotherapy and cognition: International cognition and cancer task force recommendations for harmonising preclinical research

Cancer survivors who undergo chemotherapy for non-CNS tumours often report substantial cognitive disturbances that adversely affect quality of life, during and after treatment. The neurotoxic effects of anti-cancer drugs have been confirmed in clinical and pre-clinical research. Work with animals has also identified a range of factors and underlying mechanisms that contribute to chemotherapy-induced cognitive impairment. However, there is a continuing need to develop standard cognitive testing procedures for validation and comparison purposes, broaden the search for biological and neurochemical mechanisms, and develop improved animal models for investigating the combined effects of treatment, the disease, and other potential factors (e.g., age, stress). In this paper, a working group, formed under the auspices of the International Cognition and Cancer Task Force, reviews the state of pre-clinical research, formulates strategic priorities, and provides recommendations to guide animal research that meaningfully informs clinical investigations.

[Cognitive decline in geriatric oncology: Trends, evaluation and treatment]

Cancer prevalence increases with aging. Prevalent or incident neurocognitive disorders are frequent in geriatric oncology. Cognitive decline associated with cancer increases the risk of under or over-cancer treatment and makes therapeutic decisions complex. In this context, we present tools to optimize cognitive impairment screening, identification of underlying mechanisms and specific treatments. Geriatric specialists intervention can help global care, social services utilization and patient's orientation when ambulatory cares become difficult.

Cognitive Effects of Cancer and Cancer Treatments

As the population of cancer survivors has grown into the millions, there has been increasing emphasis on understanding how the late effects of treatment affect survivors' ability to return to work/school, their capacity to function and live independently, and their overall quality of life. This review focuses on cognitive change associated with cancer and cancer treatments. Research in this area has progressed from a pharmacotoxicology perspective to a view of the cognitive change as a complex interaction of aspects of the treatment, vulnerability factors that increase risk for posttreatment cognitive decline, cancer biology, and the biology of aging. Methodological advances include the development of (a) measurement approaches that assess more fine-grained subcomponents of cognition based on cognitive neuroscience and (b) advanced statistical approaches. Conceptual issues that arise from this multidimensional perspective are described in relation to future directions, understanding of mechanisms, and development of innovative interventions.

THE CREATIVE PSYCHOSOCIAL GENOMIC HEALING EXPERIENCE (CPGHE) AND GENE EXPRESSION IN BREAST CANCER PATIENTS: A FEASIBILITY STUDY

BACKGROUND

Biomarkers associated with inflammation and immune function are increasingly being used to examine mechanisms of the effects of mind-body therapies. Less researched are biomarkers associated with cognitive and executive functioning in the study of mind-body therapy mechanisms and effects. This study explored the feasibility of recruiting breast cancer patients (BCPs) and implementation fidelity of participation in a research project utilizing the 4-stage Creative Psychosocial Genomic Healing Experience (CPGHE), a mind-body protocol that is theorized to create epigenetic effects via targeted psychological change in emotional triggers in coping with cancer.

METHODS

Eight BCPs were identified as eligible (stages I, II, III, early phases of treatment) and five consented to one of two intervention groups (allocated to a single session or two sessions of CPGHE). Blood draws were examined pre- and post- intervention for a stress/inflammation gene expression marker, Nuclear Factor kappa-B (NF-kB), and three markers associated with synaptic plasticity undergirding cognitive and executive functioning: Early Growth Response 1 (EGR1), activity-regulated cytoskeleton-associated protein (Arc), and brain-derived neurotrophic factor (BDNF).

RESULTS

One consented BCP dropped out due to illness. The remaining four adhered to the 4-stage CPGHE protocol and found the CPGHE experience beneficial. Blood samples for the gene expression results were collected and processed according to planned protocol without incident.

CONCLUSION

Implementing the CPGHE and achieving good adherence among a sample of BCPs is feasible. Processing of blood samples collected from BCPs for gene expression data is also feasible.

Impact of new generation hormone-therapy on cognitive function in elderly patients treated for a metastatic prostate cancer: Cog-Pro trial protocol

Background

New generation hormone-therapies (NGHT) targeting the androgen signalling pathway are nowadays proposed to elderly patients with metastatic castration-resistant prostate cancer (CRPCa). The impact of these treatments on cognitive function has never been evaluated whereas cognitive impairment may have an impact on the autonomy and the treatment adherence. The aim of this study is to prospectively assess the incidence of cognitive impairment in elderly men after treatment by NGHT for a metastatic CRPCa.

Methods/design

The Cog-Pro study is a multicentre longitudinal study including CRPCa patients ≥70 years old treated with NGHT (n = 134), control metastatic prostate cancer patients without castration resistance treated with first generation androgen deprivation therapy (n = 55), and healthy participants (n = 33), matched on age and education. Cognitive, geriatric and quality of life assessment and biological tests will be performed at baseline, 3, 6 and 12 months after start of the treatment (inclusion time). The primary endpoint is the proportion of elderly patients receiving a NGHT who will experience a decline in cognitive performances within 3 months after study enrollment. Secondary endpoints concern: autonomy, quality of life, anxiety, depression, cognitive reserve, adherence to hormone-therapy, comparison of the cognitive impact of 2 different NGHT (abiraterone acetate and enzalutamide), impact of co-morbidities and biological assessments.

Discussion

Evaluating, understanding and analyzing the incidence, severity of cognitive impairments and their impact on quality of life, autonomy and adherence in this group of patients with advanced disease is a challenge. This study should help to improve cancer care of elderly patients and secure the use of oral treatments as the risk of non-observance does exist. Our results will provide up-to date information for patients and caregivers on impact of these treatments on cognitive function in order to help the physicians in the choice of the treatment.

Trial registration

NCT02907372, registered: July 26, 2016.

Chemotherapy and Post-traumatic Stress in the Causation of Cognitive Dysfunction in Breast Cancer Patients

Background

Cancer-related cognitive dysfunction has mostly been attributed to chemotherapy; this explanation, however, fails to account for cognitive dysfunction observed in chemotherapy-naïve patients. In a controlled, longitudinal, multisite study, we tested the hypothesis that cognitive function in breast cancer patients is affected by cancer-related post-traumatic stress.

Methods

Newly diagnosed breast cancer patients and healthy control subjects, age 65 or younger, underwent three assessments within one year, including paper-and-pencil and computerized neuropsychological tests, clinical diagnostics of post-traumatic stress disorder (PTSD), and self-reported cognitive function. Analysis of variance was used to compare three groups of participants-patients who did or did not receive chemotherapy and healthy control subjects-on age- and education-corrected cognitive performance and cognitive change. Differences that were statistically significant after correction for false discovery rate were investigated with linear mixed-effects models and mediation models. All statistical tests were two-sided.

Results

Of 226 participants (166 patients and 60 control subjects), 206 completed all assessment sessions (attrition: 8.8%). Patients demonstrated overall cognitive decline (group*time effect on composite z -score: -0.13, P = .04) and scored consistently worse on Go/Nogo errors. The latter effect was mediated by PTSD symptoms (mediation effect: B = 0.15, 95% confidence interval = 0.02 to 0.38). Only chemotherapy patients showed declined reaction time on a computerized alertness test. Overall cognitive performance correlated with self-reported cognitive problems at one year ( T = -0.11, P = .02).

Conclusions

Largely irrespective of chemotherapy, breast cancer patients may encounter very subtle cognitive dysfunction, part of which is mediated by cancer-related post-traumatic stress. Further factors other than treatment side effects remain to be investigated.