Fitness as treatment for cancer

January 18, 2015   Fitness Articles
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Abstract

Cancer is a serious illness which affects many people in their lives and currently causes most deaths in the western world. Although cancer is primarily treated by chemotherapy and radiotherapy, physical activity and/or exercise has positive effects on therapy related fatigue, daily functioning, quality of life, muscle strength, physical fitness and risk of developing secondary cancer in (ex)-cancer patients. In addition, fitness as treatment for cancer positively affects inflammatory mediating factors, which are related to developing and maintaining cancer.. Moreover it has been shown that the risk of developing cancer decreases as a result of training. These effects strongly depend on training intensity, training volume and how well exercise guidelines are followed.

Introduction

According to a recent report, in 2015 there will be a 40% increase in cancer diagnoses compared with 2000.1 This increase can partly be explained by an increase in life expectancy and population.1 On the positive side, cancer survival rates have increased from 30% and 45% to 45% and 60% in 2001 for men and women respectively. Cancer related deaths, however, are expected to continue to rise.1 Cancer is often treated with radio- or chemotherapy or a combination of these two. These therapies are employed to combat the tumor itself.2 However, cancer patients often suffer from many different other conditions, which can greatly affect daily functioning, quality of life or even therapy succes.2 Moreover, cancer can be caused by an unhealthy lifestyle or inactivity, which causes being overweight or even obesity, resulting in a disregulation of cytokines which can promote cancer growth.3,4 The International Agency for Research on Cancer estimates that being overweight or obese and inactivity causes over 25% of cancers worldwide.5 Seeing the importance of exercise in maintaining or achieving a healthy body composition and or lifestyle, this article aims to review the effects of resistance and cardiovascular training in cancer patients.

Physiology of cancer

Although a complete description and explanation on how cancer is caused and the processes accompanying tumor growth, the most basic mechanisms concerning cancer will be explained to form a background for the reviewed articles below. Almost always cancer si caused by a mutation in the DNA or another abnormal activation of genes that regulate cell growth or celdivision.6 When this regulation is disturbed, it results in unhindered cell growth of the damaged cell, forming a tumor which disrupts function of tissues nearby. The kind of tissue affected determines the sort of cancer and can have large consequences.6 Mutation or other abnormal activation of genes that regulate cell growth is caused by ionizing radiation from for example X-ray pictures and other ionizing radiation, certain chemicals such as cigarette smoke, but regular cell damage as well.6 In addition, certain inflammatory factors which normally regulate the immune system, also known as cytokines, play an important part in causing several forms of cancer.7 Some forms of cancer can even be caused by viruses. When a tumor is allowed to grow, depending on the type of cancer, it can spread through the body causing loss of function where it spreads, claiming nutrients necessary for other processes in the body, which can ultimately lead to death.7

Effects of training on cancer risk factors

Physical Activity is known as an effective intervention to reduce risk factors for cancer such as being overweight or obese.8 Although some research has found no positive effects of increasing physical activity on breast cancer risk,9 most studies indicate that physical activity reduces risk of developing cancer.8,10,11 These differences in study outcomes are explained by the inverse relation between cancer risk and exercise intensity.8 In other words, the higher the intensity and/or volume of the training generally is, the lower the risk of developing cancer. Alongside other positive effects of training on body composition and therefore being overweight or obese, it has a positive effect on cytokine regulation such as C-Reactive Protein (CRP), Tumor Necrosis Factor Alpha (TNF-a) and Interleukin-6.12 A disturbed regulation of these cytokines strongly correlates with cancer risk.13

Effects of training on cancer patients

Not only does exercise have a positive effect on developing cancer, it can be very useful for cancer patients during their treatment. Research has shown that women diagnosed with breast cancer have a better chance of survival when they have an active lifestyle than when they are sedentary. Moreover, the risk of dying from causes other than cancer reduces as well.14 Physical training during cancer treatment has a positive influence on quality of lie, cardiovascular fitness, physical functioning and fatigue.15 Both resistance and cardiovascular training are recommended for breast cancer patients undergoing chemotherapy.16 The combination of both training modalities is shown to be effective in prostate cancer patients undergoing chemotherapy and androgen depressors. These patients increased muscle mass, strength, physical functioning and balance. 17

Effects of training in cancer survivors

In cancer survivors it has been shown that it is very important to remain physically active, or, when one is not yet active enough, increase physical activity. This reduces the risk of developing co morbidities such as a secondary cancer, osteoporosis, obesity or cardiovascular disease, or it prevents it altogether.2

Discussion

From the studies reviewed above it can be concluded that resistance and/or cardiovascular exercise and an active lifestyle have positive effects on risk factors for developing cancer,8,10,11 increase or maintain functioning during (chemo)therapy,15,16,17 and decrease risk of developing comorbidities after surviving cancer.6 These results emphasize the importance of an effective training programme to increase or maintain health. This is further underlined by studies investigating (ex-)cancer patients who were not stimulated to exercise effectively. This resulted in increased fatigue during chemotherapy,19 an increase in bodyweight and risk in developing cardiovascular disease,21 and even an increased risk of dying compared with patients who performed regular exercise.15

It should be kept in mind that the studies reviewed in this article mostly focussed on breast- or prostate cancer patients. It is to be expected that exercise will confer the same benefits in patients with other forms of cancer, however care should be taken. Cancer can take many forms and not all have the same symptoms and limitations.2 Although increasing physical activity is a proven method to increase health and functioning in cancer patients and survivors,11,14,18,19 there appears to be a clear dosis-response relationship between training intensity and volume and health benefits.8,21 In other words, the higher the intensity of the training and/or volume, the better the effects on health and functioning for the patient.

Despite the reviewed studies deliver proof that exercise has many positive health related effects for cancer patients, it is possible that exercise can be impeded by the side effects of for example chemotherapy.22 On the other hand, to achieve an as large as possible training effect, it is imperative that cancer patients train according to proper training guidelines, but they seem to have more difficulty in achieving this compared with healthy persons.23 It is therefore often necessary that the (ex-)cancer patients are accompanied by a competent personal trainer or therapist during their training to achieve and maintain positive health and training effects.

Conclusion

Cardiovascular and resistance exercise and an active lifestyle are important interventions to keep the chance of developing cancer as small as possible, but helps patients during therapy to maintain strength and cardiovascular endurance, counter fatigue, to maintain or improve daily functioning and quality of life and even to reduce risk of mortality during or after cancer treatment. Several organisations such as The American Cancer Association and The International Agency for Research on Cancer strongly recommend cancer patients to perform a training programme specially designed for them and underline the value of increasing physical activity. Finally a well-designed training programme is effective in preventing or reducing co-morbidities which often occur after a successful treatment of cancer as a result of increased bodyweight and/or decreased daily functioning

References

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