Effectiveness of specific types of structured physical activities in the rehabilitation of post-mastectomy women: a systematic review

Introduction

Physiotherapeutical interventions in the form of physical activity contribute to an increased range of motion in the upper limbs, higher muscle strength in both the upper and lower limbs, overall aerobic endurance, and improved quality of life in the post-mastectomy patients [1]. As a rule, those components are the subject of comprehensive assessment within one year of concluding the oncological treatment management [2]. However, information on the long-term evaluation is not available.
As the long-term outcomes of interventions are not the subject of regular monitoring, this may lead to much reduced physical activity, since very few post-mastectomy women conform to the recommended volume of such an activity.
In fact, over two-thirds of the post-mastectomy women do not meet the requirements for physical activity, namely 150 minutes of moderate-intensity physical activity, or 75 minutes of moderate-to-vigorous physical activity (MVPA) per week [3]. It would appear that oncological rehabilitation is very much oriented towards the short-term goal of completing the maximum achievable level of fine motor skills, especially in view of the fact that daily physical activity recommendations are not effectively followed by patients. Furthermore, as Biskup et al. noted, 1/3 of woman treated for breast cancer had a medium and high falls-risk [4].
This supposition is further corroborated by Mason et al., who demonstrated that the number of patients that conform to the established physical activity norms within 10 years of mastectomy drops by almost one third, i.e. from 34 to 21.4% [5]. This result may be considered surprising, since physical activity at the level of 10 MET-hours/week (an equivalent of five 1-hour walks at a steady pace of 4.8 km/h) is required, with a view to appreciably reducing the risk of a patient’s premature death due to breast cancer [6].
Having said that, patients fail to conform to the WHO recommendations on the required scope of physical activity, consequently rendering them ineffective. Additionally, the recommended scope of physical activity might well be inadequate for the purpose.
One of the arguments in favor of this assertion was provided in a systematic review by Kyu et al., who showed that morbidity among persons who were exercising at submaximal heart rate levels and with an energy expenditure of > 8000 METs/week (an equivalent of two hours of jogging five times per week) was lower by 14%, than among those whose energy expenditure did exceed 600 METs/week (five 30-min walks at a pace of 4.8 km/h per week) [7]. Morbidity due to breast cancer in the group of subjects who often engaged in exercise at submaximal intensity was lower by 21% [6]. For comparison, radiotherapy as an adjuvant therapy reduced breast-cancer-related morbidity over the span of 10 years by 19.3-35% [8].
The purpose of their review did not consist in explaining the actual mechanism of cancer prevention aided by a pursuit of physical activity of moderate and sub-maximal intensity. Having said that, in 2015, Pedersen et al. came up with a review study mining specific data on the impact of physical activity and likely mechanisms of its effectiveness, including therapeutic management in support of cancer treatment. They highlighted the reduction of tumor growth thanks to several mechanisms, e.g. “vascularization and blood perfusion, increasing immune function, tumor metabolism” [9]. These mechanisms, further corroborated by the results described in the study by Kyu et al., seem to be an interesting starting point, with a view to pursuing further research into the matter.
The present review aimed to determine which specific type of physical activity is most commonly pursued among post-mastectomy women, as well as which specific type of structured exercise programs proves functionally the most beneficial for them.

Material and methods

Search strategy

Two investigators conducted independent searches across four databases with PubMed, EBSCO, BASE (Bielefeld Academic Search Engine) and SciELO publications released between January 2016 and June 2016. The following search terms were used: physical activity, breast cancer, randomized clinical trial, PA, RCT, physical activity regiment, strength training, endurance training, aerobic, working age.

Article selection

Articles were selected by two independent investigators. Studies whose scope overlapped were excluded. Reports regarding the studies in which randomization had not been applied, or in which selection had been quasi-random (https://en.wikipedia.org/wiki/Low-discrepancy_sequence), were also disregarded.

Exclusion criteria

All studies which reported other types of oncological events within the study group were excluded, and so were the study protocols, materials used for information purposes only, and all meta-analyses.

Types of compared measurements

The following study variables were evaluated: range of motion of the upper limbs (goniometric measurements), aerobic endurance (VO2max, VO2peak, results of the six-minute walk test – 6MWT), strength of the upper (grip strength) and lower limbs (leg press), relative appendicular skeletal muscle mass, severity of fatigue symptoms (FAQ – Fatigue Assessment Questionnaire, SCFS – Schwartz Cancer Fatigue Scale, FSS – fatigue Severity Scale, MFI – Multidimensional Fatigue Inventory, FQL – Fatigue Quality List), quality of life (the EORTC QLQ-C30 questionnaire of the European Organization for Research and Treatment of Cancer), SF-36 – the short form (36) health survey (variables comprising fatigue, depression symptoms, and anxiety), anthropometric data (lean body mass, fat mass %, body fat %, METs, total body mass), and information-processing rate (trail making test).

Evaluation of research quality

After the selection of the articles, they were checked in the PEDro database to evaluate methodological restrictions. Five out of eight articles included in the systematic review were found, with a mean score of 6.2 (4–8) points in the database.

Results

The total number of original papers found in all four research databases was 110. The final analysis was conducted for eight papers. Physical activity interventions in women after mastectomy included programs consisting of aerobic exercise (n = 4), muscle strengthening exercise (n = 2), and mixed aerobic and muscle strengthening exercise (n = 2). Exercise time (20–90 minutes) varied depending on a specific type of activity. Strength training regimen significantly increased the muscle strength, ranging 12.2–50%, depending on a specifically applied method of measurement, and a respective muscle group. The results for the upper limbs and torso muscles increased by 12.2% (Bench Press), strength of the knee extensors increased by approximately 17.5% (Leg Press), and appendicular skeletal muscle mass also significantly increased.

Aerobic exercise

Interventions involving aerobic exercise were performed from 6 to 12 weeks, one to three times per week, in sessions of 20–60 minutes. It was established that the results were followed up in the long-term (six months) in 16.6% of the studies on aerobic exercise. Exercise load was calculated based on HRmax or VO2max results or the Borg scale. Although higher performance in relation to the control group was generally observed in the 6MWT test (n = 2, p < 0.01), one of the studies did not report a difference in the distance covered during this test. Aerobic exercise reduced fatigue regardless of the applied research method. One study demonstrated increased QOL, while another did not corroborate these results (i.e. QOL variables comprising fatigue, depression symptoms, and anxiety, were found diminished) (Table 1).

Muscle strengthening exercise

Interventions featuring muscle strengthening exercise were performed for periods of 12–13 weeks, twice a week, in sessions lasting from 60 to 90 minutes. Two studies reported the long-term follow-up of the outcomes. Exercise load was calculated based on the percentage of the 1RM and arbitrarily selected weight.

Mixed aerobic and muscle strengthening exercise

Interventions involving mixed aerobic and muscle strengthening exercise were performed within a span of 12–18 weeks, twice a week, in 60-minute sessions. The long-term follow-up of the results lasted 4–6 months (n = 2). It was demonstrated that maximal oxygen uptake (VO2max, VO2peak) increased, when compared against the control groups. No significant differences were observed regarding the quality of life, using different research tools (n = 2). The results achieved via mixed interventions lasted 4–6 months.

Discussion

Regular physical activity can reduce morbidity by 20–30%, depending on the specific type of disease [10]. Its efficacy was confirmed in more than 25 chronic conditions [10]. Nevertheless, the dependence between the actual volume of exercises performed and the result of the intervention must be emphasized. Kyu et al. demonstrated that high-intensity exercise at the level of 8000 METs/week reduced the risk of premature death due to breast cancer by 21% [7]. It seems interesting that a tenfold increase in exercise intensity, compared to the 600 METs/week recommended as the normal level of physical activity and treated as the reference value in the present review, yields a 7% decrease in morbidity. According to some authors, considerable energy expenditure expressed in the metabolic equivalent reduces morbidity by as much as 26%. The results expressed in METs, raise the question as to whether this variable is suitable for the estimation of anti-inflammatory effects; however, these particular effects of moderate- and high-intensity exercise are associated with reduced morbidity due to breast cancer [11]. At least three discrepancies seem to offer persuasive rationale for the pursuit of further, in-depth studies. Firstly, 60–75 minutes of moderate-intensity physical exercise per day merely mitigates the adverse everyday effects of a sedentary lifestyle [12]. Moderate-intensity exercise thus only helps maintain overall fitness, but it fails to contribute to its further development. Secondly, very high intensity of physical exercise proposed by Kyu et al., i.e. two hours per every day of the week, does not appear to be overly effective. Finally, reporting physical activity in terms of METs in the studies focused on breast cancer, seems to be reasonable, but it fails to address the metabolic reaction and associated hormonal response, which offer vital information in terms of a physiological perspective. The above notwithstanding, a metabolic equivalent is recommended by the American College of Sports Medicine as a measure of physical exercise intensity in post-mastectomy women [13]. Furthermore, this method is also recommended by the American Heart Association for the assessment of the intensity of physical exercise [14]. High-intensity physical activity seems to be a preventive measure of some significance in oncology at large. Kraemer et al. noted increased levels of the growth hormone, cortisol and the insulin-like growth factor 1 (IGF-1) in their literature review focused on the hormonal response after muscle strengthening exercise [15]. Furthermore, research indicates that both types of physical activity improve the patients’ self-esteem, which can be explained by increased concentration of β-endorphin associated with the stimulation of hypothalamic-pituitary-adrenal (HPA) axis. This is due to the anti-inflammatory aspect (cytokines) and the balance between angiogenesis and apoptosis, in which the vascular endothelial growth factor plays a role of an inflammatory mediator. Both being overweight and/or obese affected the therapeutic outcomes in patients as bona fide contributing factors [16]. It is worth noting that only the women treated with aromatase inhibitors were able to stay truly committed to exercising throughout an entire year. The fact that as many as 30% of oncological patients did not complete physical activity programs also bears appreciable significance [17]. The present findings should therefore be taken into account when designing specifically structured, physical rehabilitation programs.

Study limitations

The study limitations may consist in the fact that presently available research tools applied for evaluation of physical activity are both diverse and non-uniform in character. Biskup et al., in their study addressing physical activity as a contributive factor in maintaining post-mastectomy health, showed a challenging nature of the research focused on comparing academical studies evaluating overall effectiveness of post-surgical intervention outcomes, while using the diversity of research tools [25]. In the present, systematic review of literature, the research tools applied in the assessment of different components of physical activity differ significantly between studies. Lack of commonly acknowledged gold-standard procedures for measuring physical activity and its individual components in breast cancer patients, seems an obvious conclusion. Such a gold-standard should be developed, while making due allowances for patients’ age stratification as well as provide a possibility of broad assessment of potential adverse events, e.g. falls-risk [27].

Conclusions

1. Aerobic exercise is the most common type of physical activity pursued by post-mastectomy women.
2. The diversity of research tools effectively contributes to impossibility to clearly establish which specific physical exercise models boast the largest potential for yielding the highest functional benefits in post-mastectomy women.

Conflict of interest

The authors declare no conflict of interest.

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Address for correspondence:

Marek Zak
Faculty of Medicine and Health Sciences
The Jan Kochanowski University
ul. IX Wiekow Kielc 19
25-317 Kielce, Poland
Phone: +48 41 349 69 09