There is clear evidence from prospective studies that higher levels of physical activity are associated with a lower risk of postmenopausal breast cancer with a dose–response relationship, though there is little evidence in relation to frequency, duration or intensity of physical activity [190]. There is more limited research evidence indicating that physical activity may protect against premenopausal breast cancer [190].

The literature also indicates that for those who have been diagnosed with breast cancer, a prior history of exercise offers some reduction in the risk of death from breast cancer [91, 94, 106]. A systematic review found that pre-diagnosis physical activity significantly reduced all-cause mortality (by 18%), and breast cancer mortality in women with BMI <25 kg/m² but not those with higher BMI [91]. Another meta-analysis found that those who reported high lifetime recreational physical activity pre-diagnosis had a significantly lower risk of all-cause mortality (18% reduction) and breast cancer-related mortality (27% reduction) compared to those who reported low or no recreational physical activity pre-diagnosis [106].

More recent pre-diagnosis physical activity was also associated with a significant reduction in risk of all-cause death and breast cancer-related death [106].

A study in women with breast cancer found that women who were active (approximately 2–3 h brisk walking per week) in the year prior to diagnosis had a 31% lower risk of death compared with inactive women [94].

Systematic reviews and meta-analyses indicate that physical activity confers benefits in those diagnosed with breast cancer in terms of decreased all-cause mortality, breast cancer mortality and breast cancer recurrence [15, 91, 106]. There is an inverse relationship between physical activity and all-cause and breast cancer-related death, and breast cancer events (breast cancer progression, new primaries and recurrence) [106]. There is also evidence that post-diagnosis physical activity reduces all-cause mortality regardless of BMI [91]. Thus, physical activity in and of itself confers benefits.

In women who have previously been inactive, increased activity after diagnosis confers protection, however, decreasing activity can increase risk greatly. A study found that compared with women who were inactive before and after diagnosis, those who increased their physical activity had a 45% lower risk of death, and those who decreased their physical activity had a fourfold greater risk of death [94]. Thus, even if a woman has been previously inactive, engaging in increased physical activity is beneficial and should be strongly encouraged. See Table 6.2 for some facts and figures.

A recent study comparing the benefits of walking versus running post-diagnosis in breast cancer survivors found that running is associated with significantly greater reductions in breast cancer mortality than walking [192]. However, it should be noted that those who are already much fitter and healthier would be more likely to choose to run than those who aren’t. Any recommendation of whether to walk or run would depend on pre-existing lower limb musculoskeletal conditions, such as arthritic pain, or biomechanical abnormalities, and the individual’s weight. The interesting finding was that the amount of exercise that afforded protection was greater than current general public health recommendations for physical activity; i.e. 150 min/week or 30 min, 5 times/week [192]. This suggests that in breast cancer survivors, at least, the goal shouldn’t merely be to satisfy the general public health recommendations, but to exceed these.

A review of 13 cohort studies conducted between 1989 and 2001 found that the majority reported an association between increasing levels of exercise and decreased prostate cancer risk. Sixteen out of 27 studies performed between 1976 and 2002 found reduced risk in men who were most active, with the average risk reduction being 10–30% [179].

The literature supports the contention that higher levels of physical activity are associated with reduced risk of dying from prostate cancer or other causes [22, 103].

Benefits have been found for both non-vigorous and vigorous activity:

Walking has been found to be beneficial in reducing risk of all-cause mortality and prostate cancer-specific mortality in men with prostate cancer [103]. It seems that brisk walking confers more protection than slow walking in terms of lower risk of all-cause mortality [103] and risk of disease progression [148]. Table 6.3 sets out some of the research findings.

However, what is often missed in designing studies into physical activity is that there are many other associated factors that may impact beneficially on health––for example, walking with a friend (social and peer support) or dog (pet therapy) or merely allocating some ‘me time’ that contributes to happiness and therefore is likely to improve body function. Such activity usually improves exercise compliance. Thus, caution needs to be taken in interpreting exercise studies conducted under clinical conditions which don’t take these other beneficial factors into account.

There is clear evidence from systematic reviews that exercise confers benefits on men diagnosed with prostate cancer, including improved quality of life, improved lower body strength, exercise capacity, and fitness level and decreased cancer-specific fatigue [23, 128]. Vigorous exercise in men has been found to be associated with larger and more regular vessel morphology in prostate tumors (in contrast, in animal models it has been found that small and irregularly shaped vessels in prostate tumors were associated with fatal prostate cancer) [181].

Research has demonstrated that exercise during and after treatment has been found to positively impact on quality of life in prostate cancer survivors, improve cardiovascular fitness and self-esteem and reduce the risk of incontinence [20, 39, 129, 188]. Moderate physical activity both during and after treatment of cancer can help to maintain or increase muscle mass and reduce fat mass and to improve cardiovascular fitness, self-esteem and quality of life (QOL) [39, 187]. Resistance and strength training is especially important to maintain muscle and bone mass for men with prostate cancer who have been prescribed androgen deprivation therapy [69]. Research has demonstrated that men undergoing androgen deprivation therapy can safely participate in resistance training without an adverse effect on their testosterone levels [69].

There is a relationship between abdominal adiposity and risk of particular cancers. The World Cancer Research Fund/American Institute for Cancer Research 2nd Expert Report found convincing evidence that body fatness is a cause of colorectal cancer with a dose–response relationship, and probable evidence for an association between abdominal fat and increased risk of pancreatic, endometrial and postmenopausal breast cancer [190]. BMI is highly associated with increased risk of colorectal cancer in men, with abdominal adiposity showing the strongest association [134].

Weight gain in adulthood has been linked with a range of cancers. The World Cancer Research Fund/American Institute for Cancer Research 2nd Expert Report advised that there substantial and consistent epidemiological evidence of an increased risk of postmenopausal breast cancer with increasing amount of weight gained in adulthood, with an apparent dose–response relationship. It concluded that adult weight gain is a probable cause of this cancer [190].

There is sufficient evidence of a cause-effect relationship between obesity and cancer, however the mechanisms by which obesity may increase the risk of cancer may differ depending on the type of cancer [149, 187]. For example, obesity may be associated with low-grade inflammation which is involved in the pathogenesis of cancer (as well as Type II diabetes and other cardio-metabolic conditions and many other chronic conditions) [134]. Insulin pathways (specifically hyperinsulinemia) appear to mediate the relationship between obesity and colon cancer [79, 187]. For evidence in relation to mechanisms, readers are referred to other reviews.

Despite many studies that indicate an association between overweight and obesity with cancer, there is much less research on the effects of weight loss on risk of cancer [187].

Several studies have demonstrated that weight loss following bariatric surgery reduces risk of cancer [1, 33, 119, 173]. For example, one study found that weight loss after bariatric surgery significantly reduced cancer death by 60% [1]. A systematic review that included 13 studies and 54,257 participants confirmed that bariatric surgery was associated with reduced cancer risk in morbidly obese persons [31].

Other studies have implicated weight loss in reduction of cancer recurrence. For example, the Women’s Nutrition Intervention Study that investigated a low-fat dietary intervention in breast cancer survivors found that the average weight of those in the intervention group (target 15% of energy from fats) significantly decreased whilst those in the control group increased. Those in the intervention group had significantly less breast cancer recurrence at 60 months. It is possible that not only the low-fat diet but the weight loss contributed to the results [18].

Overweight and obesity can lead to insulin resistance and Metabolic Syndrome and diabetes. Chronically elevated insulin levels can lead to tumor growth [28] and insulin resistance has been linked to breast cancer [101, 174]. These conditions are risk factors for cancer. Weight loss has been found to be associated with a reduced risk of incidence of diabetes [84].

Physical activity can play a role in reducing weight in those who are overweight or obese, however physical activity in itself has a protective effect against cancer, quite independent of its effect on weight [190]. Of interest is the finding from the Nurses’ Health Study that examined associations between BMI and physical activity in 116,564 women aged 30–55 years. They found that increased adiposity and reduced physical activity are both strong and independent predictors of death from any cause, and that weight gain in adulthood was also a strong and independent risk factor for early death, regardless of exercise level. When the data for cancer-related deaths was examined, the trend was similar- increasing adiposity was associated with an increased risk of death in all three categories of physical activity. Women who were lean and exercised more had the lowest mortality [89]. These results suggest that physical activity may not fully counteract the negative impact of adiposity on risk of all-cause mortality, and nor does leanness counteract increased mortality due to inactivity. Thus, reducing weight for those cancer patients who are overweight and increasing physical activity would both seem important. Simply losing weight without increasing physical activity may not be enough either. Those with cancer who are at a healthy weight still need to exercise, given the independent protective effect of physical activity.

In addition, research suggests that exercise combined with diet is more effective than physical activity alone in reducing weight. A systematic review that investigated the effect of exercise on body weight in men with prostate cancer found that exercise alone did not lead to weight loss (though most of the trials in the review were focused on the impact of exercise on quality of life and fitness rather than decreasing weight); it was diet or diet plus exercise that was found to lead to decreased body weight [128]. It is also important to add in respect to any change in body weight with diet and/or aerobic exercise for men with prostate cancer being treated with androgen deprivation therapy, that any loss of body weight may not be due to a reduction in body fat levels but rather a loss of muscle and bone mass. Hence the importance of including resistance training to maintain or increase muscle and bone mass in this group of clients [69].

The issue of weight loss and physical activity needs to be considered carefully, particularly in overweight or obese people. Weight loss has traditionally been the target in overweight or obese people, and health authorities have recommended physical activity for obesity reduction based on the belief that the ensuing weight loss is the important factor [154]. However, is it the weight loss or the increased cardio-respiratory fitness that should be emphasised as the goal of physical activity, in particular as a treatment strategy in cardio-metabolic disease and longevity [76]? Research suggests it is increased levels of physical activity that is the more important.

The literature supports the contention that increasing cardio-respiratory fitness is more important than reducing body weight in improving cardio-metabolic health and all-cause mortality [76, 105, 110]. Increased levels of cardio-respiratory fitness are associated with lower risks of cancer (as well as all-cause mortality) [97]. There is much evidence to indicate that increased levels of physical activity is associated with significant decreases in cardio-metabolic diseases as well as all-cause mortality [140], but also that a reduction in BMI is not associated with decreased incidence of all-cause mortality [19, 85, 110], unless the individuals were unhealthy [85]. A meta-analysis of 26 studies found that where individuals are healthy and obese, intentional weight loss has no effect on all-cause mortality but where individuals are unhealthy and obese, intentional weight loss reduced all-cause mortality by 27% [85].

There is sufficient research that indicates that benefits associated with increased physical activity are not simply related to weight loss [154]. A review of 28 exercise training studies of 8–24 weeks duration found that there were significant gains in cardio-respiratory fitness and significant decreases in waist circumference (marker of abdominal obesity), visceral fat levels and cardio-metabolic risk factors, despite minimal or no change in body weight of those participating [154]. Studies have shown that waist circumference and visceral fat significantly decrease with exercise, with little or no weight loss [152, 153], however there are other studies that have shown the waist circumference and visceral fat decreases with weight loss [154]. Increased physical activity and related improved cardio-respiratory fitness has been found to be associated with significant reductions in coronary artery disease and CVD mortality, independent of weight or BMI [108, 185], and significant reductions in several cardio-metabolic risk factors, with no or little change in body weight [47, 177]. Research indicates that weight loss is not required in order to achieve significant increases in aerobic capacity, and results in significant reductions in blood pressure and resting and submaximal heart rate and positive improvements in mood in overweight/obese men and women [105].

Australian-accredited exercise physiologist Dr Ian Gillam highlighted that changes in body weight itself is a poor indicator of changes in body composition, and that it is the visceral body fat levels that are key determinants of metabolic health and not decreases in body weight [76].

Cancer-related fatigue (CRF) is defined as ‘a persistent, subjective sense of tiredness related to cancer or cancer treatment that interferes with usual functioning’ [126]. It affects an estimated 70–100% of cancer patients, seriously interfering with their quality of life [2]. Almost all patients who undergo treatment experience CRF, with almost half reporting it as severe, and it can last for months or years after treatment [132]. CRF is associated with several co-morbidities including sleep problems, depression and pain [132].

There is substantial evidence from systematic reviews [45, 51, 104] and individual studies that regular exercise can reduce fatigue in patients with cancer [40, 41, 168]. In one study of men with prostate cancer with or without androgen deprivation therapy (ADT), 24 weeks of resistance training and aerobic exercise both mitigated fatigue and in the longer term, increased muscle and bone mass, improved body composition and had additional benefits for quality of life [70, 168]. In another study, colorectal cancer patients undergoing chemotherapy who engaged in moderate intensity walking and a flexibility program for 20–30 min/day, 3–5 days/week had significant improvements in cancer-related fatigue (CRF), depression, anxiety, cardiopulmonary function and emotional, functional and physical well-being and quality of life [40, 41].

Studies in men with prostate cancer have indicated that exercise is associated with increased quality of life, muscular fitness and physical functioning, and reductions in BMI and body weight [63, 70, 73, 104, 178]. A systematic review in men with prostate cancer found that exercise was associated with improvements in muscular endurance, aerobic endurance and overall quality of life and reduced fatigue [104]. It may also improve muscle mass, muscular strength, functional performance and health-related social and physical quality of life [104]. Strength training is especially important for patients with prostate cancer undergoing ADT [79]. The effects were found to be greater for those engaged in group-based exercise than home-based exercise [104], which is in contrast with another meta-analysis that found comparable benefits [62]. Both low-intensity and high-intensity exercise training interventions have been found to improve cardio-respiratory fitness in breast cancer and prostate survivors, though four months later, only the high intensity group maintained their cardio-respiratory fitness [115].

Interval walking training where the intensity of the training alternates (i.e. three min of low intensity then three minutes of high intensity walking), has been found to better control blood glucose in people with type 2 diabetes, in comparison with continuous walking [102]. A study in type 2 diabetics found that whilst no exercise was associated with a deterioration of glycaemic control, continuous walking had no impact on glycaemic control but interval walking improved physical fitness, body composition (fat mass and visceral adiposity) and glycaemic control [102]. Thus, in cancer patients who may also have diabetes, there may be benefits in trying interval walking training (providing that there are no contraindications that would prohibit this, of course).

Exercise is known to have benefits on the cardiovascular system, including lowering blood pressure. For those patients who have hypertension, research has shown that four sessions of 10-min of walking is just as effective in lowering blood pressure as 40 min of continuous walking per day [58]. Therefore, it is not necessary to have a large stretch of time for exercise––breaking exercise periods up into shorter sessions can still have benefits.

Cancer cachexia is a complex syndrome characterised by inflammation, body weight loss and continuous loss of skeletal muscle mass (with or without loss of fat) and is a cause of death in a substantial proportion of those with cancer [7, 82]. Cachexia is associated with reduction in muscle strength and endurance, and can be extremely debilitating, reducing quality of life and the ability to perform daily activities. The underpinning mechanisms include lipolysis, changes in muscle metabolism and systemic inflammation [81].

The rationale for the use of exercise to address cancer cachexia is that it is a condition underpinned by systemic inflammation, where muscle strength and endurance are decreased. Exercise can increase muscle strength and endurance in healthy conditions (depending on the type of physical activity) [7], and exercise is able to exert an anti-inflammatory effect and can counteract the muscle catabolism by increasing protein synthesis and reducing protein degradation [5, 81]. Muscle wasting is only one of the features of cachexia, so exercise is an important strategy to address the underlying systemic inflammation associated with cachexia, not just the muscle wasting. Resistance training and aerobic training may both be able to address this underlying systemic inflammation [71, 113], with several studies of aerobic exercise demonstrating decreased inflammation [11, 157].

Systematic reviews also provide some limited data that exercise can assist in cancer cachexia. A meta-analysis demonstrated that globally, there is a positive effect of exercise in addressing cachexia [142]. Other evidence comes from individual studies, with more focussed on strength training rather than aerobic training (possibly due to the focus on muscle wasting associated with cachexia). See Table 6.5 for some examples.

Anaemia is often associated with cancer cachexia (up to one third will have anaemia at diagnosis) and contributes to weight loss, reduced exercise capacity and changes in energy homeostasis [26]. Animal studies have found that when mice with tumors that had a significant decrease in haematocrit were exercised, their condition worsened [7]. The American Cancer Society Expert Panel advise that cancer survivors with severe anaemia delay exercise until anaemia is improved [6].

Evidence from case studies, cross-sectional studies, experimental studies and systematic reviews/meta-analyses indicate that exercise can reduce the symptoms of depression and anxiety [25, 36, 43, 46, 51, 100, 118, 166, 193], though a few have found otherwise [45, 180]. Whilst many studies have focussed on aerobic exercise (i.e. walking and jogging programs), others have demonstrated the benefits of non-aerobic, resistance-training programs. Studies that have compared the two types of exercise, aerobic and resistance training, have found they are similarly effective in reducing depression symptoms [21, 55, 71, 116]. Furthermore, the benefits of exercise in reducing depression were found to be maintained months after cessation of the studies [48, 54]. Table 6.6 sets out a few of the studies on exercise, depression and anxiety.

Body image can often take quite a battering in women who have had mastectomies. There are many studies in women with breast cancer including a meta-analysis (of 56 studies) [51] which have demonstrated the positive effects of physical activity on quality of life and positive body image [40, 41, 63, 144, 175]. For example, women with breast cancer who undertook a 12-week exercise regime had significantly improved body image compared with controls, and a non-significant reduction in distress [144].

Exercise may provide an important opportunity for peer support, socialising and unloading of stress. Men with prostate cancer undergoing a structured exercise program reported positive changes in self-efficacy, reduced treatment-related side effects, a shift towards a positive outlook and desire to engage more actively in life as a result of the program. The study found that exercise physiologists provided important information as well as emotional and social support and that peer support of others with prostate cancer that occurred as part of the exercise program was important to these men, in particular sharing the experience of prostate cancer and the social connections that developed as part of the program [37].

As discussed in a previous chapter, nearly 45% of cancer patients experience problems sleeping, almost three times the proportion in the general population. Disturbed sleep in cancer can be related to pain (due to the disease itself or treatment side effects), psychological stress, and/or the treatments (chemotherapy, radiation, hormone therapy, surgery) and their side effects. Exercise can help combat disrupted sleep. See Chap. 4 for a discussion on sleep.

Pain is experienced in 45–59% of cancer patients and survivors [32], and can be the result of the tumor itself or the cancer treatment including surgery, chemotherapy, radiation therapy, targeted therapy, diagnostic procedures and supportive care [135]. Pain severity and duration correlate with risk of depression [135].

The general pain literature indicates benefits of exercise in relieving chronic pain, largely through the induction of endorphins but also via its positive effect on mood, relaxation of muscles and its anti-inflammatory effect [143]. There is evidence that in cancer survivors, exercise is also beneficial in reducing pain. For example, approximately 20–50% breast cancer survivors experience breast or chest wall pain, impacting negatively on quality of life and research has found that exercise is able to reduce these symptoms and improve quality of life [189]. Aromatase inhibitors used to treat postmenopausal women with hormone-receptor positive breast cancer to help prevent recurrence can cause joint pain and stiffness; exercise (two supervised weight-training and resistance-training sessions, and 150 min of moderate aerobic exercise a week) was found to significantly reduce joint pain and stiffness (20% reduction) compared to women who didn’t exercise (3% reduction) [93].

Many cancer survivors, including those with central nervous system (CNS) tumors and non-CNS tumors, suffer the difficulty of cognitive impairment which can include short-term memory, attention, concentration and executive functioning problems and difficulties with word-finding and multi-tasking [9, 96, 132, 159, 183]. It can occur prior to, during and after treatment [96, 183] and it can interfere with their functional independence [159]. Cancer treatments that causes cognitive decline include chemotherapy, radiation therapy, immune modulation, hormone therapy, pain medications and brain surgery. The extent of the cognitive impairment can be quite severe and impact substantially on the physical and mental well-being of cancer survivors. A subset of cancer patients appear to be more vulnerable. Patients receiving chemotherapy were found to be 2.25 times more likely to have cognitive decline after chemotherapy compared with a control group [172]. Up to 75% of breast cancer survivors can experience this during chemotherapy and it can persist for years after treatment in 20–35% of these women [96]. The mechanisms underpinning this cognitive decline are not well known.

There have been few studies that have investigated whether exercise can improve cognitive impairment associated with cancer and its treatment, though there are some currently underway [80, 86]. Exercise such as Chinese Tai Chi, a form of gentle exercise, has been shown to improve memory, attention and executive function in cancer survivors, as well as psychological and physical health [147].

Incontinence is a side effect of prostate surgery for a substantial proportion of men with prostate cancer. A study of men post-prostatectomy found that men who were not obese and were active were 26% less likely to be incontinent than men who were obese and inactive. The study found that physical activity might confer some protection even in those men who were obese, since the prevalence of incontinence at 58 weeks was similar in the obese/active group and the non-obese/inactive group (25% vs. 24% incontinent) [188].

Childhood cancer survivors have a higher risk of developing secondary cancers as well as other diseases [8]. Exercise plus diet interventions have been found to reduce the risk of co-morbid disease and prevent functional decline in childhood cancer survivors [53].