Determinants of chronic fatigue in disease-free breast cancer patients: a cross-sectional study

P. Servaes1,+, S. Verhagen2 and G. Bleijenberg1

Netherlands Fatigue Research Group, Departments of 1Medical Psychology and 2Medical Oncology, University Medical Centre Nijmegen, The Netherlands

Received 15 June 2001; revised 12 September 2001; accepted 25 September 2001.


    Abstract
 Top
 Abstract
 Introduction
 Patients and methods
 Results
 Discussion
 References
 
Background

Quality of life after cancer treatment becomes more important as the number of long-term survivors increases. This study aimed to investigate complaints of fatigue after treatment for breast cancer.

Patients and methods

The study patients were 150 women who had finished curative treatment for breast cancer by a mean of 29 months before commencement of this study. Measurements included computerised questionnaires and a daily Self-Observation List.

Results

Thirty-eight per cent of the sample were severely fatigued, compared with 11% in a matched sample of women without a history of cancer. No association was found between fatigue and former treatment. The ‘severely fatigued disease-free breast cancer patient’ scored more ‘problematic’ on psychological well-being, functional impairment, sleep disturbance, physical activity, social support, neuropsychological and social functioning compared with the ‘non-severely fatigued disease-free breast cancer patient’. Furthermore, the severely fatigued patients had a lower sense of control with respect to their fatigue complaints and stronger breast cancer- and psychologically-related attributions with regard to the causes of fatigue compared with the non-severely fatigued patients. Regression analyses indicated that sleep disturbance, physical activity and causal attributions contributed significantly to the subjective experience of fatigue.

Conclusions

Severe fatigue is a problem for almost 40% of the sample of breast cancer survivors. Severe fatigue is related to physical, psychological, social, cognitive and behavioural factors.

Key words: breast cancer, fatigue, multidimensional measurement, post-treatment


    Introduction
 Top
 Abstract
 Introduction
 Patients and methods
 Results
 Discussion
 References
 
Fatigue is a subjective experience that affects everybody. For healthy individuals it might be a protective, sometimes even pleasant regulatory response to physical or psychological stress. It seems to maintain a healthy balance between rest and activity. Controversially, for people with specific diseases fatigue often becomes a major distressing symptom. Based on results of research with patients with chronic fatigue syndrome, multiple sclerosis and other chronic diseases we know that fatigue is a multidimensional phenomenon, which consists of physical, psychological, social, cognitive and behavioural aspects [1, 2].

For patients with cancer, fatigue has been described as a major concern during treatment and in advanced stages of the disease [3, 4]. In recent (quality of life) studies, fatigue has also been mentioned as a frequent complaint by disease-free cancer patients (long) after curative treatment for cancer has ended [513]. Furthermore, in three studies [1416], patients who had been treated for breast cancer 20, 28 and 16 months before, respectively, scored significantly higher than non-cancer comparison subjects on standardised self-report measures of fatigue. In addition, in a large sample of breast cancer survivors, there was a subgroup of survivors who did report heightened levels of fatigue relative to women in the general population [17]. Contrary to these results, no differences in fatigue scores were found in two other studies [18, 19] comparing disease-free cancer patients 9 and 22 months, respectively, following radiotherapy with healthy controls.

The possible causes of fatigue, long after treatment for cancer has finished, are still unknown. It is a logical expectation that fatigue can be predicted by preceding illness or former treatment modalities. However, most studies do not support a relationship between off-treatment fatigue and type of treatment, time since diagnosis, or treatment and disease stage at diagnosis [79, 13, 15, 16, 1820]. Nevertheless, these results have to be interpreted with caution because results might have been influenced by the research design. For instance, in a sample of patients who were all treated with radiotherapy, it is hard to demonstrate a relationship between off-treatment fatigue and radiotherapy.

Physical, psychological, social, cognitive and behavioural factors might also be related to fatigue, and play a role in the perpetuation of fatigue, long after treatment for cancer has finished. These relationships have been the object of investigation in only a few studies. In those studies post-treatment fatigue seemed to be related to depression, anxiety, quality of sleep, use of catastrophising as a coping strategy and menopausal symptoms [1520].

In assessing chronic fatigue in patients with several chronic diseases, a multidimensional assessment method has identified nine dimensions, namely fatigue severity, psychological well-being, functional impairment in daily life, sleep disturbance, physical activity, neuropsychological impairment, social functioning/social support, self-efficacy and causal attributions [1]. These dimensions appear to be relatively independent, meaning that each dimension uniquely contributes to the description of a patient. Based on clinical experience and indications in the literature, the object of the current study is to assess these nine dimensions of fatigue in a group of disease-free breast cancer patients. In addition, an age-matched sample of women without a history of cancer is included.

In this article we will answer the following four research questions: (i) how many disease-free breast cancer patients experience severe fatigue (long) after treatment for cancer was finished; (ii) is fatigue severity in disease-free breast cancer patients associated with former treatment modalities (type of operation, type of adjuvant therapy, duration of treatment and time since treatment ended); (iii) how can the ‘severely fatigued disease-free breast cancer patient’ be described, with use of the above mentioned dimensions and (iv) what is the contribution of the physical, psychological, social, cognitive and behavioural dimensions to the fatigue severity dimension in disease-free breast cancer patients?


    Patients and methods
 Top
 Abstract
 Introduction
 Patients and methods
 Results
 Discussion
 References
 
Sample
To select a relatively homogeneous group of patients, all patients had to be treated according to the protocol of the Comprehensive Cancer Centre East for premenopausal breast cancer patients. Furthermore, they had to be younger than 50 years old by the time of primary diagnosis and had to have completed treatment for breast cancer for a minimum of 6 months and a maximum of 70 months before the study commenced. They also had to have no evidence of disease recurrence at the time of participation. Finally, all patients had been checked for side-effects of previous anti-cancer treatment within 3 months after treatment. None of the patients included in the study were anaemic at the time.

Most participating patients (120 of the 150) were asked to bring along a female family member, friend or colleague who was not >5 years younger or older than the patient. This woman had to be healthy (no chronic disease) and had never to have been treated for cancer in the past.

Recruitment procedure
Patients were recruited from one university hospital and six regional hospitals. At the university hospital and three regional hospitals, all patients who met the eligibility criteria were initially informed about the study by mail with an introductory letter from their oncologist. At the other three regional hospitals, patients were informed by their oncologist during control visits. In the following week, patients were contacted by telephone by the psychologist-researcher (PS). Those patients who agreed to take part in the study were invited to the department of Medical Psychology of the University Hospital, Nijmegen. The Ethics Committees of all participating hospitals agreed the study.

Measurement
Patients and their female friends were invited to the research institute where they were asked to fill out several computerised questionnaires. In addition, they filled out a daily Self-Observation List (SOL) during a period of 12 days. Severity of fatigue was reported four times a day in this list. Furthermore, quality of sleep, level of activity, hours of household activities and hours of work outside the house were reported once a day.

Each of the nine investigated dimensions was represented by several measures. The reason behind this lies in the fact that each instrument contributed uniquely to a certain dimension.

Fatigue severity was measured by the fatigue severity subscale (CIS-fatigue) of the Checklist Individual Strength (CIS) [1]. The CIS is a 20-item questionnaire which was designed to measure four aspects of fatigue during the previous 2 weeks, namely: fatigue severity (eight items), concentration (five items), motivation (four items) and physical activity (three items). Each item was scored on a seven-point Likert scale. High scores indicated a high level of fatigue, a high degree of problems with regard to concentration, low motivation and a low level of physical activity. Based on research with chronic fatigue syndrome patients, a score of 35 or higher on the subscale fatigue severity indicates severe feelings of fatigue [1]. Based on scores of healthy controls, a score between 27 [mean score for healthy adults plus one standard deviation (SD)] and 35 indicated heightened experience of fatigue [21]. In addition, fatigue was measured with the Daily Observed Fatigue (DOF) score of the SOL [22]. DOF was reported four times a day on a five-point scale (0–4). Total scores ranged from 0 to 16. Available norm scores of 53 healthy subjects indicated that healthy adults have a mean DOF score of 1.6 (SD 1.4) [2].

Psychological well-being was measured with the Beck Depression Inventory for primary care (BDI-pc), the Spielberger Trait Anxiety Inventory (STAI) and the Rosenberg Self-Esteem Scale (RSE). The BDI-pc was used in analysing the data, to prevent an overlap between the physical aspects of fatigue with the somatic symptoms of depression. This shortened version of the BDI [23] had seven items and was composed of cognitive and affective symptoms only [24]. A score of 4 or more was indicative of clinical depression. The STAI is a standardised self-report questionnaire designed to measure trait anxiety [25]. A score of 50 or more was considered indicative of clinical anxiety [26]. The RSE measured global self-esteem and consisted of 10 items [27]. Furthermore, the anxiety, agoraphobia, depression, somatisation, obsessive-compulsive behaviour, interpersonal sensitivity and hostility subscales of the Symptom Checklist (SCL-90) were used [28]. Finally, the emotional functioning subscale of the Quality of Life Questionnaire-C30 of the European Organisation for Research and Treatment of Cancer (QLQ-C30) was included [29].

Functional impairment was measured with the subscales home management, work, and recreation and pastimes from the Sickness Impact Profile (SIP) [30]. Furthermore, the role functioning subscale of the QLQ-C30 was used. In addition, hours of work (outside the home and household activities) were registered in the SOL.

Sleep disturbance was measured with the Groninger Sleep Quality Scale [31]. This questionnaire consisted of 14 items on problems with falling asleep, restless sleep, early awakenings in the morning and general quality of sleep. Each item was scored on a yes/no format. A total score of sleep disturbance was derived from this questionnaire. Furthermore, the sleep/rest subscale of the SIP and the sleep subscale of the SCL were used. Finally, quality of sleep (general quality of sleep, difficulties falling asleep, restless sleep and early awakenings) was registered daily in the SOL.

Physical activity was measured with the physical functioning subscale of the QLQ-C30, the physical activity subscale of the CIS, and the mobility and ambulation subscales of the SIP. In addition, physical activity was registered once a day in the SOL.

Neuropsychological functioning was measured with the cognitive functioning subscale of the QLQ-C30, the concentration subscale of the CIS and the alertness behaviour subscale of the SIP.

Social functioning/social support was measured with the social functioning subscale of the QLQ-C30, the social interaction subscale of the SIP and the van Sonderen Social Support Inventory (SSL) [32]. The SSL was divided into the SSL-I (amount of social support), the SSL-D (discrepancies between amount of social support and desired amount of social support), and the SSL-N (amount of negative interactions).

Self-efficacy, a sense of control over fatigue symptoms, was measured with the subscale ‘internal locus of control’ of the Multidimensional Health Locus of Control (MHLC) and the Self-Efficacy Questionnaire (SEQ). The MHLC measured control beliefs with respect to health in general [33, 34]. The SEQ consisted of five questions that measured sense of control with respect to fatigue [35].

Causal attributions with regard to fatigue complaints were measured with the Causal Attribution List. This questionnaire consisted of nine items divided over two subscales, psychological (e.g. ruminate, sleep problems) and breast cancer-related attributions (e.g. surgery for breast cancer, adjuvant therapy for breast cancer). For each item, patients were asked to indicate their opinion regarding the cause of their fatigue complaints on a four-point scale (1 very applicable to 4 not at all applicable). Internal reliability of this questionnaire was good. The subscales psychological- and breast cancer-related attributions had alpha’s of 0.81 and 0.79, respectively.

Statistical analysis
Data analysis was performed using SPSS (version 8.0). Descriptive statistics were used for description of the sample. t-tests, chi-square and general linear model (GLM)-general factorial were performed testing the differences between groups. In order to examine the contribution of the physical, psychological, social, cognitive and behavioural dimensions to the dimension of fatigue severity, linear regression analyses (enter-method) was performed.


    Results
 Top
 Abstract
 Introduction
 Patients and methods
 Results
 Discussion
 References
 
Description of the samples
Two-hundred and sixty-three disease-free breast cancer patients were contacted for this study. Most of these patients (248) were sent an introductory letter from their oncologist while only 15 patients were contacted during control visits. One hundred and fifty-five patients (59%) agreed to participate in the study. Non-participants did not differ from the participants with regard to age, type of surgery, radiotherapy and time since treatment completion. However, the non-participants received chemotherapy less often: 41% compared with 66% (chi-square; P <0.001). Therefore, duration of treatment was significantly lower for non-participants (4 compared with 6 months for participants; t-test; P <0.001). Reasons for non-participation were: participation takes too much time (n = 24), too emotional to participate (n = 12), wanting to move on with their lives (n = 12), did not feel like taking part (n = 9), concurrent major health problems (n = 8), not able to contact (n = 7), problems with transport (n = 6), too tired to participate (n = 1), other reasons (n = 6) and unknown (n = 23).

Five of the 155 participants were excluded for analyses since they dropped out during baseline assessment. One had concurrent major health problems (thyroid gland disorder), one had disease recurrence, one had medical problems with regard to breast reconstruction and two had major psychological problems.

Seventy-eight patients brought a female family member, friend or colleague along to the hospital. Information about demographic characteristics of the two samples is listed in Table 1. The sample of disease-free breast cancer patients was comparable with the sample of control women with regard to age, marital status, education and employment. However, the percentage of disablement insurance act was higher in former breast cancer patients than in the women without a history of cancer.


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Table 1. Demographic characteristics of both samples
 
Information about the medical characteristics of the patient sample is listed in Table 2. The majority of the participating women were treated with mastectomy. A small group (13%) did not receive any adjuvant therapy while the others received radiotherapy, chemotherapy or both. Duration of treatment was defined as the period from the time of surgery until the end of adjuvant therapy. Time since diagnosis was defined as the day of diagnosis until the day of participation in the current study. Finally, time since treatment was defined as the period from the end of adjuvant therapy until the day of participation in the current study.


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Table 2. Medical characteristics of the patient sample
 
Research question 1. How many disease-free breast cancer patients experience severe fatigue (long) after treatment for cancer was finished?
The mean CIS-fatigue score of the total patient sample was 28.5 (SD 13.6) compared with 19.4 (SD 11.0) in the sample of women without a history of cancer (t-test; P <0.001). Fifty-seven patients (38%) met the ‘cut-off’ criteria for severe fatigue (i.e. CIS-fatigue >=35) while an additional 24 patients (16%) had a score between 27 and 35. The group of patients who had a CIS-fatigue of 35 and higher were referred to as ‘severely fatigued disease-free breast cancer patients’. The other patients were referred to as ‘non-severely fatigued disease-free breast cancer patients’. In the control group, nine women (11%) met the ‘cut-off’ criteria for severe fatigue.

The mean DOF score of the total patient sample was 2.9 (SD 2.2, minimum 0, maximum 9.5). In comparison, the mean DOF score was 1.6 (SD 1.3, minimum 0, maximum 4.5) in the sample of women without a history of cancer (t-test; P <0.001). The mean DOF score of the severely fatigued disease-free breast cancer patients was 4.6 (SD 2.1) and that of the non-severely fatigued disease-free breast cancer patients was 1.9.

Research question 2. Is fatigue severity associated with former treatment modalities?
To test the association between fatigue severity on the one hand, and type of operation (lumpectomy or mastectomy) and type of adjuvant therapy (no adjuvant therapy, radiotherapy, chemotherapy or both) on the other hand, a GLM-general factorial was conducted. The dependent variable was the CIS-fatigue. Fixed factors were the variables type of operation and type of adjuvant therapy. Results indicated that there was no main effect of type of surgery (P = 0.281), no main effect of adjuvant therapy (P = 0.852) and no interaction effect (P = 0.912). This meant that mean fatigue severity scores did not differ significantly for those patients who underwent mastectomy (mean CIS-fatigue score 27) and those who underwent lumpectomy (mean CIS-fatigue score 31). Furthermore, mean fatigue severity scores were equal for those patients who received radiotherapy (CIS-fatigue score 28), chemotherapy (CIS-fatigue score 28), both radiotherapy and chemotherapy (CIS-fatigue score 29), and those who did not receive adjuvant therapy (CIS-fatigue score 28).

The association between severe fatigue and length of treatment (1, 2–6 or >6 months) and time since treatment (6–12, 13–24, 25–36, 37–48, 49–60 or >60 months) was also tested with a GLM-general factorial. The dependent variable was the CIS-fatigue. Fixed factors were the variables length of treatment and time since treatment. No main effect of length of treatment (P = 0.387), no main effect of time since treatment (P = 0.938) and no interaction effect (P = 0.950) were found.

Research question 3. How can the ‘severely fatigued disease-free breast cancer patient’ be described?
In Table 3, comparisons have been made between severely fatigued disease-free breast cancer patients, non-severely fatigued disease-free breast cancer patients and women without a history of cancer, with regard to the dimension of psychological well-being, functional impairment in daily life, sleep disturbance, physical activity, neuropsychological impairment, social functioning, self-efficacy and causal attributions.


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Table 3. Dimensions of fatigue [means (SD)]: comparisons between severely fatigued disease-free breast cancer patients, non-severely fatigued disease-free breast cancer patients and control women (general linear model-general factorial)
 
Results with regard to the psychological well-being dimension are consistent. Severely fatigued disease-free breast cancer patients have a lower mean score of emotional functioning, they are significantly more depressed and more anxious than non-severely fatigued disease-free breast cancer patients. In addition, severely fatigued disease-free breast cancer patients have a lower self-esteem and higher scores on the agoraphobia, somatisation, obsessive-compulsive behav-iour, interpersonal sensitivity and hostility subscales of the SCL compared with the non-severely fatigued disease-free breast cancer patients. More specifically, according to the results of the BDI-pc and STAI, in the group of severely fatigued disease-free breast cancer patients 12% can be considered as clinically depressed but not clinically anxious, 2% as clinical anxious but not clinically depressed and 19% as both clinically depressed and anxious. These percentages are 2, 3 and 1%, respectively, for the group of non-severely fatigued disease-free breast cancer patients. Non-severely fatigued disease-free breast cancer patients are comparable with regard to psychological well-being to women without a history of cancer.

On the subscales of the QLQ-C30 and SIP that were used to measure functional impairment in daily life, severely fatigued disease-free breast cancer patients reported being more functionally impaired than did non-severely fatigued disease-free breast cancer patients. Furthermore, both groups (severely fatigued and non-severely fatigued) reported more functional impairment in daily life than women without a history of cancer. On the SOL, no significant differences were found with regard to number of days working, number of days with household activities and hours of work or household activities per day within a 2-week period, between the three different samples. However, controls worked more hours per day in comparison with both patient groups.

On the sleep disturbance dimension, severely fatigued disease-free breast cancer patients report having more problems with sleep than non-severely fatigued disease-free breast cancer patients. The two groups did not differ in the frequency of early awakenings. Scores of non-severely fatigued disease-free breast cancer patients were comparable with scores of women without a history of cancer, except for the sleep/rest subscale of the SIP. Non-severely fatigued disease-free breast cancer patients scored more problematic on this subscale in comparison with control women.

With regard to the physical activity dimension, severely fatigued disease-free breast cancer patients reported less physical functioning on all used measures compared with non-severely fatigued disease-free breast cancer patients. Non-severely fatigued disease-free breast cancer patients were comparable with respect to physical activity with women without a history of cancer.

The same applied for the dimension representing neuropsychological impairment. Scores on all subscales indicated that severely fatigued disease-free breast cancer patients reported having more problems with regard to memory and concentration than non-severely fatigued disease-free breast cancer patients. This latter group had comparable scores to women without a history of cancer.

On the social functioning/social support dimension, severely fatigued disease-free breast cancer patients reported less social functioning and more impairment with regard to social interactions than non-severely disease-free breast cancer patients. In comparison with the control group, both patient groups reported significantly more problems on the social interaction scale of the SIP. With regard to social support all three groups reported having the same amount of social support. However, severely fatigued patients experience more negative interactions and a higher discrepancy between the amount of social support and desired amount of social support than did the non-severely fatigued patients and control women. That is to say, severely fatigued patients wished that they were receiving more social support than they felt they were actually receiving.

Within the self-efficacy dimension, no differences were found between severely fatigued disease-free breast cancer patients and non-severely fatigued disease-free breast cancer patients with respect to the internal locus of control of health in general. This means that patients in both groups believed to the same extent that they would remain healthy or ill as a result of their own behaviour. However, severely fatigued patients had a lower sense of control with respect to fatigue than non-severely fatigued patients. Thus, severely fatigued patients thought to a lesser extent than did non-severely fatigued patients, that they could exert influence on their fatigue complaints.

Finally, on the dimension of causal attributions, severely fatigued disease-free breast cancer patients reported more psychological and more breast cancer-related attributions with regard to fatigue complaints than did non-severely fatigued disease-free breast cancer patients. In other words, patients who experienced severe fatigue attributed their fatigue complaints, more often, to the fact that they were diagnosed and treated for breast cancer in comparison with those who experienced only moderate fatigue. In addition, they also more often indicated that their fatigue complaints could be a result of the fact that they often ruminated, experienced trouble sleeping, etc.

Research question 4. What is the contribution of the physical, psychological, social, cognitive and behavioural dimensions to the fatigue severity dimension in disease-free breast cancer patients?
Regression analyses were performed to examine the contribution of psychological well-being, functional impairment in daily life, sleep disturbance, physical activity, neuropsychological impairment, social functioning, self-efficacy and causal attributions to fatigue severity. Two analyses were done, one with the CIS-fatigue severity score as the dependent variable, and the other using the DOF score as the dependent variable. Independent variables were those questionnaires or subscales of questionnaires within the other eight dimensions that correlated most highly with one of the dependent variables. For the dimensions physical activity and social functioning two measures were selected for the regression analyses, because within these dimensions one measure correlated highest with the CIS-fatigue severity score and the other one with the DOF score. Within all the other dimensions, one measure correlated highest with both the CIS-fatigue severity score and the DOF score.

Results indicate that in both analyses, questionnaires representing the dimensions of sleep disturbance (SIP-sleep/rest), physical functioning (CIS-activity or QLQ-C30-physical functioning) and causal attributions (breast cancer-related attributions) contributed significantly to the fatigue severity dimension. Furthermore, the dimension of psychological well-being (SCL-depression) contributed significantly to the CIS-fatigue severity score. In total, 52% of the fatigue severity subscale of the CIS were predicted, and 43% of the DOF score (Table 4).


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Table 4. Linear regression analysis to predict fatigue
 

    Discussion
 Top
 Abstract
 Introduction
 Patients and methods
 Results
 Discussion
 References
 
In this study, a strikingly large part (38%) of a group of women who were treated for breast cancer in the past turned out to be severely fatigued. This is significantly higher than the percentage in a matched control group of women without a history of cancer. Although severe fatigue might have been associated with treatment modalities while patients were undergoing treatment, this association could not be found long after treatment for breast cancer was completed. Results failed to find significant associations between severe fatigue on the one hand, and type of operation, type of adjuvant therapy, length of treatment and time since treatment on the other hand. As mentioned in the Introduction, these results correspond to the majority of recent findings in the literature.

In an attempt to describe the ‘severely fatigued disease-free breast cancer patient’ on several dimensions, we found that severe fatigue long after completion of treatment for breast cancer is associated with several physical, psychological, social, cognitive and behavioural factors. The strength of the association observed between fatigue and depressive symptomatology is interesting in light of the fact that one of the measures of depression used in this study (BDI-pc) included items that reflect cognitive and affective symptoms of depression but not somatic symptoms. Thus, the relationship cannot be explained as overlap of the physical aspects of fatigue with somatic symptoms of depression. However, our results suggest that, although in some patients the depression–fatigue association cannot be ruled out as a possible explanation for the experience of fatigue after treatment for cancer, it is an incomplete description of the underlying process. Within the group of severely fatigued disease-free breast cancer patients, 69% cannot be considered as clinically depressed.

From results of the dimension ‘functional impairment’ it can be concluded that severely fatigued disease-free breast cancer patients see themselves as more impaired with regard to role functioning, home management, and recreation and pastimes than do non-severely fatigued disease-free breast cancer patients. However, on the SOL, severely fatigued disease-free breast cancer patients reported the same amount of household activities and work outside the house as non-severely fatigued disease-free breast cancer patients. These results probably indicate that disease-free breast cancer patients have to resume their household activities, no matter whether they feel fatigued or not. Furthermore, it could be that it is very important for women in our society to resume their work outside the home after treatment for cancer (for financial or social reasons).

With regard to sleep disturbance, it seems logical that when one does not sleep well, fatigue complaints are maintained. Causes of sleep problems have not been extensively investigated. It is possible that sleep problems are the result of the experience of tension, fear and anxiety that is related to the uncertainty regarding the future. Furthermore, in breast cancer patients, who often become menopausal because of chemotherapy, an increased frequency of night-time vasomotor symptoms (i.e. night sweats) could produce disruptive effects on sleep [36]. Additional research is needed to clarify this issue.

The relationship between fatigue and physical activity has rarely been investigated in the literature, and only during active treatment for cancer [3739]. Results suggest a negative relationship between physical activity and fatigue. In addition, sports or walking programmes during treatment for cancer report positive results, although follow-up analyses are absent [40, 41]. Results from our study also suggest that after treatment for cancer lower physical activity is related to more severe fatigue.

On the dimension of social support we found that severely fatigued disease-free breast cancer patients experience less social support than they would like. This perceived lack of social support may result from the fact that family and friends do not expect their wife, mother or friend to experience fatigue or any other complaints more than a year after treatment for breast cancer.

In general, non-severely fatigued disease-free breast cancer patients are comparable with women without a history of cancer on the above described dimensions. The only differences between these two groups were found on several subscales of the SIP (namely home management, work, recreation and pastimes, sleep/rest and social interaction) and on one subscale of the SOL (number of hours of work per day).

On the ‘self-efficacy’ dimension, severely fatigued disease-free breast cancer patients had a lower sense of control with respect to their fatigue complaints than did non-severely fatigued disease-free breast cancer patients. This finding is consistent with results of studies with chronic fatigue syndrome patients and multiple sclerosis patients. In these patient populations, a negative self-efficacy was found to have a direct negative causal effect on fatigue severity [35].

In summary, results from this study indicate that severe fatigue is a problem for nearly 40% of the disease-free breast cancer patients. Furthermore, there are no indications for a relationship between off-treatment fatigue and former treatment modalities. Finally, severe fatigue is associated with several physical, psychological, social, cognitive and behavioural factors. Regression analyses indicated that depression, physical inactivity, the need to sleep and rest during the day and the tendency to attribute fatigue complaints to the breast cancer experience, contribute significantly to the severity of fatigue.

Nevertheless, it is important to note that there are also many breast cancer survivors who have scores comparable with those of women without a history of cancer with respect to fatigue severity, psychological well-being, sleep disturbance, physical activity, neuropsychological impairment, social functioning and social support. These women thus seem to function quite well about 2 years after treatment for breast cancer.

The strengths of this study include the use of a comprehensive multidimensional assessment of fatigue and the reliance upon different self-report measures for each dimension. In addition, use of the SOL in which fatigue is registered four times a day, and sleep, activity and work are registered once a day, constituted an advance over entire reliance upon retrospective measures. Furthermore, we could use an empirically validated cut-off point for severe fatigue, based on norm scores of fatigue from several groups of patients and healthy controls [21]. Finally, the inclusion of an age- and gender-matched control group leads to useful results.

In future, specific attention should be paid to the way in which physical, psychological, social, cognitive and behav-ioural factors contribute to the course of fatigue after successful treatment for cancer, using a longitudinal design. More knowledge about the perpetuating factors of off-treatment fatigue will enable us to develop interventions to reduce fatigue complaints in severely fatigued disease-free cancer patients.


    Acknowledgements
 
This research was funded by the Dutch Cancer Society.


    Footnotes
 
+ Correspondence to: Dr P. Servaes, Medical Psychology (118), University Medical Centre Nijmegen, P0 Box 9101, 6500 HB Nijmegen, The Netherlands. Tel: +31-24-3619387/3613608; Fax: +31-4-3613425; E-mail: P.Servaes@cksmps.azn.nl Back


    References
 Top
 Abstract
 Introduction
 Patients and methods
 Results
 Discussion
 References
 
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