One in two men and one in three women will be diagnosed with cancer during their lifetime. The good news is that with earlier detection and improved treatments, the survival rate for many common cancers is increasing.
One of the most common questions people who have been diagnosed with cancer ask is, “How can I stop it coming back?”
We know physical activity is good for us, but what if being physically active reduced the chance of cancer coming back?
Current research aims to answer this question. And the early results are promising, suggesting the benefits of exercise for those with localised cancer may be similar to the benefits from chemotherapy. Physical activity is certainly not a substitute for having chemotherapy or other therapies, but we’re increasingly realising it’s an important part of a comprehensive treatment plan.
The evidence so far
Large long-term (epidemiological) studies of disease trends have shown that those who exercise regularly are less likely to develop breast, colon or prostate cancer than those who don’t. Estimates suggest it may reduce the risk of developing cancer by up to 60%.
We also know that physical activity reduces the risk of other diseases such as heart disease, stroke and diabetes. And physical activity helps some people manage their mood and sleep patterns.
But what if you already have cancer?
A long-term study of a large group of women in the United States, some of whom later developed breast or colorectal (bowel) cancer, found that those who self-reported higher levels of physical activity had a much lower rate (up to 50%) of cancer recurrence.
A follow up of nearly 3,000 nurses found that those doing more physical activity after being diagnosed with breast cancer decreased their risk of dying prematurely (from any cause) and reduced their risk of dying from breast cancer. Those meeting current physical activity guidelines (such as brisk walking for two hours a week) almost halved their risk of death from breast cancer compared with those who were sedentary.
Similar results were seen in the nurses who developed colorectal cancer. Those exercising more than the physical activity guideline recommendations (such as four hours of brisk walking) halved their risk of dying from colorectal cancer.
Another study in both men and women with colon cancer found that people doing more than the recommended minimum of physical activity each week reduced the risk of their cancer returning (at three years) by about half – that’s an absolute improvement of about 10%.
It was not the amount of physical activity people were doing before their cancer diagnosis that was important, but what they did after. There also appears to be a “dose-response” effect: some physical activity is better than none, but, within reason, more physical activity is better.
While promising, these observational studies, do have some problems. The amount of activity recorded is based on self report and people were not randomised to participate in a physical activity program or not – so there may be some bias, possibly with those doing better from their cancer also being more physically active.
How much exercise is enough?
Despite the limitations of the current studies, the American Cancer Society has published guidelines that recommend people with cancer avoid being inactive and return to normal daily activities as soon as possible after diagnosis. They recommend at least 150 minutes a week of physical activity, including strength training exercises at least twice a week. These guidelines were endorsed by the Cancer Council Australia.
But after cancer treatment, people rarely get back to their pre-diagnosis physical activity levels. Instead many stop or reduce physical activity during cancer treatment, not restarting when it finishes.
Only 20% to 32% of cancer survivors report meeting physical activity guidelines of 30 minutes of moderate to vigorous physical activity (such as brisk walking, running, swimming, cycling or yoga) most days of the week.
Why are the rates so low?
Remembering that many people diagnosed with cancer have physical activity levels lower than the guidelines, other concerns may stop them to get moving again. Many people don’t know how to be physically active, have worries about what they are physically able to do or have troubling side effects from their anti-cancer treatment, such as difficulty walking due to pins and needles in their feet and hot flushes.
Some people may be feeling a loss of confidence in their body or be worried about managing a stoma bag. While for others, family members may encourage them to take it easy.
Added to these concerns are the same issues confronting all of us - making time for physical activity and maintaining our motivation.
Where to from here?
Although the observational results are compelling, only a randomised controlled trial – where participants undertake either a three year supervised physical activity program or have their usual care - will provide clear evidence of the benefits of exercise. To gather this evidence, my colleagues and I are currently undertaking the Colon Health and Life-Long Exercise Change (CHALLENGE) study, in collaboration with a Canadian research group, NCIC Clinical Trials Group.
Participants from across Australia will complete fitness assessments, questionnaires measuring their mood, quality of life, sleep patterns, levels of fatigue, physical activity behaviour and health status. As we don’t know very much about how physical activity might moderate cancer recurrences, participants will provide blood samples regularly throughout the study to allow us to investigate potential mechanisms.
We will also monitor resource usage and cost-effectiveness of delivering the intervention. In the era of expensive anti-cancer therapy, effective physical activity interventions may become a very cost-effective anti-cancer treatment with the advantage of providing many other health benefits with few undesirable side effects.
While research is ongoing, there is enough evidence to show that physical activity is an important part of maintaining good health whether it’s to reduce the risk of cancer, help prevent it returning, or to help people feel better and happier during their remaining lifetime.