To examine the relationship between exercise and rehabilitation (quality of life) in cancer patients, and to offer recommendations for future research.

Studies that had been conducted and published in any language were identified through computerised searches of MEDLINE, PsycLIT, SPORTDiscus and CINAHL, and manual searches of journals. Eleven studies were found, of which 2 were unpublished conference proceedings that could not be retrieved, 2 were doctoral dissertations, and 7 were published research studies.

Study designs of evaluations included in the review

Of the 9 studies reviewed, 4 studies were RCTs, 3 were quasi-experimental studies and 2 were retrospective studies (1 case-control and 1 cohort study). One RCT was a secondary data analysis of a subset of patients from a previously conducted RCT.

Specific interventions included in the review

All empirical studies on exercise and rehabilitation of cancer patients, published in any language, were eligible for inclusion. Interventions: cycle ergometer thrice weekly, 20 to 30 minutes per session, 60 to 85% maximum heart rate for a 10 to 12 week period; cycle ergometer lasting 4 to 6 weeks including a 6-month (twice to thrice weekly) moderate intensity exercise (any activity) programme; home-based, combined walking and social support programme. Two of the 3 quasi-experimental studies and 3 of the 4 randomised controlled trials (RCTs) used an exercise intervention programme thrice weekly for 10 to 12 weeks. The other quasi-experimental study lasted 4 to 6 weeks and included a 6-month (twice to thrice weekly) moderate intensity exercise programme. The other RCT used a home-based, combined walking programme (increasing from 10 to 45 minutes over the study period, 4 to 5 times weekly for a 3 to 6 month period) and a social support programme as the intervention modality involving bi-weekly 90 minute meetings led by a nurse.

Participants included in the review

Most included a convenience sample of breast cancer patients, 7 studies considered patients at all stages of cancer, and 2 were restricted to stages I and II breast cancer cases identified through a local medical clinic or practice. Most were still undergoing active treatment, i.e. chemotherapy. One study included patients who had completed their treatment, and 2 others had a mixed population of patients currently on treatment or who had completed treatment. The retrospective case-control study attempted to identify cases through a tumour registry.

Outcomes assessed in the review

Three of the RCTs and quasi-experimental studies assessed improvement of physiologic parameters, including increases in functional capacity, i.e.peak oxygen consumption (VO2), heart rate, workload and time to achieve VO2 peak (assessed with the cycle ergometer symptom-limited graded exercise test), and lean tissue, decreases in percentage body fat, nausea and fatigue (assessed with the Cooper 12-minute Walking Test and the Karnofsky Performance Status Scale). The RCTs each measured other physiological symptoms and changes using the Symptom Check List-90-Revised, Symptom assessment scales for fatigue and nausea, the Brief Symptom Inventory, or measurements of body weight and composition; no assessment of physiological functioning was made in the 2 retrospective studies.

Improvement in psychological indicators of well-being and quality of life were assessed in 6 studies using different instruments in each study: one quasi-experimental study measured the perception of internal locus of control (Levenson LOC Scale), another measured total mood disturbance (Profile of Mood Scales), and a third measured personality traits (Freiburger Personality Inventory); the retrospective case-control study measured self esteem using the Self Esteem Rosenberg Scale, perceived health (one item 4-point ad hoc scale), and perceptions of benefits and barriers to an individual's participation in exercise (unpublished scale); the retrospective cohort study used both the Quality of Life Index for Patients with Cancer and the Perceived Barriers to Exercise Scale; and 1 RCT assessed psychological functioning using the Psychosocial Adjustment to Illness Scale, the Tennesse Self-Concept Scale, Body Image Visual Analogue Scale, and the Symptom Assessment Scale. No study provided follow-up assessments of physiological or psychological functioning after termination of the intervention programme.

How were decisions on the relevance of primary studies made?

The authors do not state how the papers were selected for the review, or how many of the authors performed the selection.

The authors do not report the method used to assess validity, or how the validity assessment was performed.

The authors do not state how the data were extracted for the review, or how many of the authors performed the data extraction.

How were the studies combined?

The studies were combined in a qualitative narrative due to the heterogeneous study designs, the variability in the type and form of exercise intervention and measurement, the data collection methods and the outcomes assessed.

How were differences between studies investigated?

The authors do not state how differences between the studies were investigated.

Of the 11 studies found, 2 were unpublished conference proceedings that could not be retrieved. Thus 9 studies were included: 2 doctoral dissertations and 7 published studies. Four of the 9 studies were RCTs, 3 were quasi-experimental designs, and 2 were retrospective (1 case-control and 1 cohort study). In the 4 RCTs and 3 quasi-experimental studies, there were 6 to 18 patients allocated to the intervention group, whilst in the 2 retrospective studies, there were 54 cases in the case-control and 71 in the cohort study.

Overall, exercise had a positive effect on physiological and psychological functioning, including functional capacity (peak VO2) body fat, nausea and fatigue, natural defence mechanisms, locus of control, mood states, self-esteem and quality of life in breast cancer patients. Specifically, some of the RCTs and quasi-experimental studies found that exercising cancer patients had improved work capacity, lower heart rates at a given power, and increased maximum workloads and time to achieve VO2 peak, as compared with non-exercising control patients. Comparable gains in functional capacity were seen between exercising patients and healthy exercising controls. Exercising cancer patients also experienced a decrease in percentage body fat and an increase in lean body mass, decrease in nausea and fatigue, and an overall improvement in natural defence mechanisms.

Psychological changes, including a decrease in total mood disturbances, an increase in perceived internal locus of control, decrease in depression, and fewer problems associated with sleeping were noted between the exercise and control groups in the intervention studies. In the retrospective studies, exercising cancer patients had higher self-esteem, better quality of life and fewer perceived barriers to exercise as compared to non-exercising patients.

Some evidence exists that exercise rehabilitation has a beneficial effect on the physiological and psychological well-being of patients with breast cancer. However, the review has identified numerous methodological limitations with the research studies reviewed, and so these results must be considered with some degree of caution.

The review had a well-defined objective. However, the review has several major methodological weaknesses. The review failed to use any explicit criteria to select studies for inclusion in the review so as to ensure that the selection of studies was objective. The relevant databases were searched to identify all possible studies in the area, but the search strategy is not stated; whether all attempts were made to identify studies in the grey literature is also unclear. It is clear from the review that both the validity and quality of the primary studies varied in terms of the methodological design, and sample and intervention characteristics. The review does not ignore this as an issue, but no attempt was made to weight the studies according to the quality of study design, with RCTs carrying more weighting than quasi-experimental design studies. Similarly, the validity of the studies was also given little attention. It may have been more informative if studies were summarised according to the type of study design, i.e. a subgroup analysis of RCTs, etc. It is also not documented how the author(s) decided on whether or not to include a study is not documented, i.e. whether this was assessed independently or whether this decision was arrived at by consensus. Thus, both issues around validity and quality have received scant attention in this review. No detail is provided in the paper about how the data were extracted from the papers or the assumptions that were made about how the data were prepared for the analysis. The studies were appropriately synthesised into a narrative review, but no priority was given to studies based on quality or sample size. Since the strength of the evidence is weak, with few RCTs conducted in the area as well as the heterogeneity of the interventions used, one cannot definitively conclude that exercise rehabilitation is beneficial to cancer patients' psychological and physiological functioning.

Research: The authors stated that, in order to ascertain the extent to which exercise may contribute to the rehabilitation of all types of cancer patients, future research studies should focus on several areas. These include: patients with varying cancers; use of well-conducted RCTs; the type of exercise intervention most appropriate in terms of intensity, frequency, timing and duration of the programmes; programmes which resemble patients' own life experiences more closely; the long-term impact of exercise on patients' quality of life and a disease-free survival; and programmes that assess many of the physiological and psychological changes, and which explore exercise recruitment and adherence problems if they occur. Thus, a clear rationale exists for future research in the area of exercise and cancer.

This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn.