Cancers form a very large group of conditions which are extremely common causes of disease, disability, suffering and death. Nearly 40% of people will be diagnosed with one or another type of cancer in their lifetime and cancer causes nearly 30% of all deaths in the UK. Cancers are also very disparate, varying from minor skin excrescences to devastatingly fast spreading and fatal malignancies. The place of exercise in the prevention and management of such a wide spread of conditions is likewise very variable.
Exercise in the prevention of cancer
It has been known for many years that some cancers are more common in physically inactive people and that the risk can be reduced by following the standard recommendation of about 30-60 minutes daily of moderate to vigorous-intensity physical activity. Cancers involved include colon, breast, uterus, gullet, gall bladder, pancreas and kidney.
Physically active men and women have about a 30-40% reduction in the risk of developing colon cancer compared with inactive persons and there is a dose-response relation, with risk declining further at higher levels of physical activity. With breast cancer, physically active women have about a 20-30% reduction in risk compared with inactive women. It appears that 30-60 minutes daily of moderate – to vigorous-intensity physical activity is needed to decrease the risk of breast cancer, and again there is a dose-response relationship. Endometrial (the lining of the womb) cancer is also less common in physically active women by a factor of about 20%.
A large meta-analysis of 1.44 million individuals found that regular physical activity reduced the risk of 13 different cancers – by 10% for the breast up to 42% for the gullet. Other cancers which were prevented by physical activity included liver, lung, kidney, stomach, womb, bone marrow (ie leukaemia), colon, rectum and bladder. The World Cancer Research Fund in 2009 estimated that 12% of colon cancers, 12% of breast cancers and 30% of endometrial cancers in the UK are related to inadequate physical activity.
Physical fitness and cancer
As might be expected there is also a relationship between cardiorespiratory fitness (CRF) and cancer risk. A low level of CRF has been found to increase cancer risk by up to 50% and to have an even greater effect on cancer mortality, reducing survival time free from cancer by as much as seven years.
Mortality from cancer has also been linked to physical activity. A 17 year follow-up study of 480,000 adults related exercise mix to risk of dying from cancer and found the risk to be reduced by 30% for aerobic exercise, 22% for muscle strengthening and an amazing 50% for the two combined.
Obesity and cancer
Closely related to lack of exercise, overweight and obesity are among the commonest contributory causes of cancer. These include gullet, myeloma, stomach, colon, rectum, biliary system, pancreas, breast, uterus, ovary and kidney. Exercise clearly has a preventive role here. In 2013, an estimated 4.5 million deaths worldwide were caused by overweight and obesity; on the basis of recent estimates, the obesity-related cancer burden represents up to 9% of the cancer burden among women in North America, Europe, and the Middle East. Body fatness and weight gain throughout the life course are largely determined by modifiable risk factors including physical inactivity. Avoidance of weight gain has been shown to reduce the risk of cancers of the colon, gullet, kidney, breast and womb.
Weight loss may be even more effective. An analysis of 180,000 women followed up for ten years found that those who lost between 2 and 4.5kg lowered their risk of developing breast cancer by 13% while those who lost more than 9k lowered the risk by 26%.
The best current estimate is that around 1% of all cancers in the UK may be related to physical inactivity (below a modest aspiration of 30 minutes five times per week) meaning that around 3,400 cases every year are linked to people doing less than government guidelines for physical activity.
Exercise in the treatment of cancer
Prehab, for short, is the use of healthy lifestyle changes before embarking on treatment – in this case before surgery, chemotherapy, radiotherapy or all three. An exercise programme can improve the patient’s general health, physical fitness and ability to withstand the rigours of the treatment regime. In the case of surgery for lung cancer for instance, physical and pulmonary function can be substantially improved with a pre-surgery exercise programme, reducing the complications of the operation and recovery period. Recovery is faster and more complete.
When it comes to the treatment of cancers, exercise is attracting increasing attention. Evidence is emerging to show that regular exercise can reduce recurrence of treated cancers after medical and surgical treatment and also prolong life. In one study of breast cancer, exercise treatment was associated with double the chance of survival over eight years and two thirds the chance of recurrence.
Patients recovering from cancer and its management have to deal not only with the effects of the disease itself but also the toxic effects of treatment which can include pain, nausea, vomiting, fatigue, anorexia, anxiety and depression. Reduction in physical capacity, muscle strength and quality of life are very common aftermaths. An exercise programme can be the ideal antidote. A systematic review of the effects of exercise in breast cancer patients found significant improvements in quality of life, cardiorespiratory fitness, physical functioning and fatigue. A meta-analysis of trials of exercise treatment in a wide variety of cancer types concluded that such treatment led to improvements in quality of life and fitness both during and after treatment.
How much exercise?
The main benefit found for the active treatment was from moderate intensity exercise but, after treatment, benefits had been derived from all forms of exercise. These include running, brisk walking, cycling, weight lifting, body weight or elastic band exercises, all of which can produce similar benefits. So far studies have not been designed to determine more exact exercise programs for specific cancer types nor the long-term effects of exercise. “…sufficient evidence is available to promote exercise to adults with cancer, and some evidence is available to promote exercise in a group or supervised setting and for a long period of time to improve quality of life and muscular and aerobic fitness”.
Cochrane reliably sums up the benefits of exercise programmes for patients with cancer and concludes that exercise has beneficial effects at varying follow-up periods on Health Related Quality of Life with improvements in physical functioning, role function, social functioning, and fatigue. Positive effects of exercise interventions are more pronounced with moderate- or vigorous-intensity than with mild-intensity exercise programmes..