The risk of developing number of different cancers is lower for those who take regular exercise than for those who do not. Similarly, fitter individuals are at lower risk than the unfit for such cancers. Examples include breast, colon, bladder, endometrial, kidney, oesophageal adenocarcinoma, gastric, non-Hodgkin lymphoma, head and neck, myeloma, myeloid leukaemia, liver, and gallbladder cancers. Quite a list.
Such associations are not a proof that exercise prevents cancer – association is not proof of causation. However there are good reasons to believe that the association does has a causative element. Some of the possible mechanisms by which higher levels of exercise and fitness might reduce cancer risk include lower body weight, increased insulin sensitivity, reduction in inflammation and changes in hormone levels.
Exercise to treat cancer
The strongest argument for using exercise as part of the cancer management regime has been the effect of increased fitness in coping with both treatment and recovery from the effects of that treatment – as well the inevitable period of low physical activity during treatment. Physical fitness has several benefits for the cancer patient before treatment – these include better tolerance for operations and chemotherapy, a reduction in the complications and severity of side effects of such treatments, shortened time in hospital after surgery and reduced risk of non-related diseases such as heart attacks and diabetes.
But does exercise improve cancer prognosis?
Until now there has been no good evidence of the impact of exercise after diagnosis of cancer, with little support for incorporating physical training into patients’ regimes. However this has changed with a recent of a trial of exercise for patients undergoing treatment for colon cancer.
In the trial, carried out in the US, UK, Australia, France, Canada and Israel between 2009 and 2023, researchers enrolled 889 colon cancer patients. Most (90%) had stage three disease. Patients were randomly assigned to take part in a structured exercise programme (445) or to receive a healthy lifestyle booklet (444).
Those in the exercise group worked with a personal trainer twice a month for coaching and supervised exercise sessions, and later once a month, for a total of three years. They were coached and supported to help them achieve set exercise goals. The weekly target was the equivalent of three to four walks of between 45 and 60 minutes, but patients could choose how they got more active. Some went kayaking or skiing, for instance.
The five year disease-free survival of the exercise group was 80% and and for the controls it was 74%. In other words the exercisers had a 28% lower risk of recurrent or new cancers than those in the control group. At 8 years, 90% of patients in the exercise program were alive vs 83% of those in the control group, which translated to a 37% lower risk for death.
Take home message
The authors of the study concluded that exercise can reduce by a third the risk of cancer patients dying of their disease, it can stop tumours coming back and it is as effective as, or more effective than, drugs. An uninvolved commentator added that many drugs get approved for this magnitude of benefit – but ” they’re expensive and they are toxic.”
Scientists are already investigating whether similar exercise regimes could improve survival for people with other malignant diseases, such as breast cancer. Even if the findings do not hold for other cancers the effect on colon cancer is highly significant. Colon cancer is the fourth most common cancer in the UK, with around 31,800 people diagnosed each year.
Will these findings affect clinical practice?
Sadly, it is unlikely that there will be a rush to set up exercise clinics for patients recovering from colon (or other) cancer. Exercise as a treatment – exercise on prescription – is just not in the sights of doctors. The medical mindset does not include the idea of prescribing exercise – even though a low level of physical fitness is well known to be a risk factor for so many degenerative diseases and even though exercise training is such an effective treatment for the same conditions.
Somehow exercise needs to become recognised as the most valuable treatment we have for the ill-effects of getting older. We need to start to measure the level of fitness as readily as we measure cholesterol level – and then be as ready to intervene with exercise prescription as we are with a statin prescription.
I can feel another blog on the prescription of exercise coming on – watch this space!
