Exercise does not cure cancer, but it can help
Today, everything is said and written about the benefits of exercise in fighting cancer—too often without sufficient scientific evidence. However, analysis of available studies allows patients to know what to expect from their investment. While exercise does not cure cancer, certain physical activity programs can help—and there is evidence to support this.
Gregory Ninot, University of Montpellier
Sport is becoming an asset in the fight against cancer. Associations offer patients the opportunity to practice karate or tai chi. Specialized cancer centers such as the Curie Institute organize group exercise or endurance classes. Companies are setting up exercise sessions via videoconference, such as V@si. And sports federations, such as the tennis federation, offer specific sessions for this audience.
Following a tailored physical activity program is one of the many "alternative therapies" that can be used to treat this condition, alongside conventional treatments. Its benefits will be discussed at the scientific conference oneffectiveness of non-drug interventions in cancer, which will be held on March 23 in Montpellier, at the initiative of the CEPS Platform.
Physical activity, long considered incidental
A brief historical overview. Before the 1980s, physical activity was of no interest to cancer professionals in France. Priority was given to treatments: surgery, radiotherapy, and chemotherapy—everything else was secondary. And rightly so, given the progress that had been made in the field.
Specialized hospitals were created in the largest cities, known as Cancer Centers (CLCC), to respond to the growing influx of patients being diagnosed at an increasingly early stage, and to set up technical facilities in appropriate premises.
Between 1980 and 2000, teams launched the first clinical research studies, particularly in Canada and the United States. For example, a prospective trial published in 1999 by an American scientist showed an improvement in the quality of life of 27 patients treated with chemotherapy for breast cancer, thanks to an eight-week physical activity program carried out at home.
Early studies mainly in breast cancer
Most of the studies available during this period were pilot studies, with numerous methodological limitations. Breast cancer predominated in these studies, making it tempting to extrapolate the results to all cancers. The physical activities analyzed were very different from one another. And they were initiated at different stages of patient care: immediately after diagnosis, before the start of treatment, or after treatment.
However, a review of the scientific literature published in 1999 confirms the significant impact of physical exercise on patients' health-related quality of life. At the time, the aim of physical activity was to improve quality of life but also self-esteem, which had been damaged by aggressive treatments such as hair loss.
The main thing was to enjoy doing sport. Patients were therefore given the choice of what to do, with the idea that they would regain their self-confidence and break out of their isolation. This was mainly done at home, encouraged by healthcare professionals and a few pioneering oncologists. The health messages were fairly basic. Described as hygiene and dietary advice, they could be summed up today by the phrase: "you need to move more when you have cancer."
Reduce fatigue, pain, and anxiety
Since the 2000s, physical activity has become a form of "supportive care" in its own right. In other words, it is now considered part of "the care and support needed by patients throughout their illness." Official recommendations indicate that it should be started as soon as possible after the patient has been diagnosed with cancer.
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The goal is threefold. First, to reduce symptoms caused by treatment and cancer itself, such as fatigue, pain, anxiety, depression, nausea, sleep disorders, lymphedema (swelling caused by poor lymph circulation), and neuropathy (nerve damage). Second, to improve overall health, physical condition, and body composition—that is, to promote muscle mass gain at the expense of fat mass, particularly abdominal fat. Finally, to prevent physical deconditioning, i.e., the vicious cycle leading to physical inactivity with all its physiological (e.g., muscle atrophy) and psychological repercussions (loss of confidence in one's physical abilities). This deconditioning is a factor in poor prognosis, reduced treatment effectiveness, and higher mortality.
Randomized controlled trials were then conducted, with converging conclusions showing a reduction in fatigue and anxiety-depressive symptoms, improved physical condition, and prevention of deconditioning. A series of meta-analyses provided the highest level of evidence, those of 2005, 2006, 2009, and 2011.
Carefully gauge the intensity of the treatment so as not to exhaust the patient.
A final meta-analysis, published in 2012, which is particularly demonstrative, concludes that a supervised physical activity program is beneficial for fatigue, based on 56 randomized controlled trials involving 4,068 patients treated for cancer. The program is supervised to ensure the safety of participants—for example, the risk of cardiovascular problems due to chemotherapy is taken into account. Supervision involves both adjusting the intensity so as not to exhaust the patient during treatment and maintaining their participation over time.
Other studies are currently being conducted on the post-cancer period, to encourage people to continue regular weekly physical activity in line with recommendations. General principles established bythe French National Cancer Institute (INCa) in 2017 provide a framework for these practices. Two other institutions, Inserm and the French National Authority for Health (HAS), will publish their recommendations this year.
These initiatives are part of a general movement towards "prescription sport," which has been applicable by decree since March1, 2017. This involves the medical prescription of adapted physical activity (APA) programs for people with chronic illnesses. Added to this is the encouragement to practice APA mentioned in the 2014-2019 Cancer Plan.
Distinguishing false promises from genuine ones
In France, there is a plethora of physical activities on offer, but they are unevenly distributed among cancer centers, clinics, medical centers, sports associations, cancer associations, companies in the sports and health sector, start-ups, and private practitioners. This proliferation of offerings is sometimes accompanied by promises that go beyond scientific knowledge, even suggesting the possibility of a cure or the prevention of recurrence.
To date, it is not possible to predict such outcomes on an individual basis. Only cohort studies, which follow hundreds of patients over time, provide indications of the role of physical activity in recovery. And even then, only in the form of probabilities. For example, analysis of 24 cohorts from different countries, comprising a total of 35,622 patients, indicates a 38% reduction in cancer mortality risk for breast cancer, colorectal cancer, and prostate cancer, according to research by a Canadian team published in 2016. This does not make sport a cure for cancer.
Clinical trials are beginning to be conducted around the world on survival and reduction of recurrence through physical activity, in combination with conventional cancer treatments, such as that of a team from the University of Alberta (Canada) on colon cancer, whose protocol was published in 2008. The first results will be known by 2020. In the meantime, there is still insufficient evidence to confirm that physical activity of a given intensity and type can influence the progression of cancer or its recurrence.
Acting on immunity, metabolism, inflammation, and neuropsychology
The basic idea is to slow down tumor progression and help prevent recurrence by specifically targeting the individual's immune, metabolic, inflammatory, and neuropsychological functions through targeted physical activity. Scientific and clinical progress still needs to be made to understand the mechanisms involved and offer the best program for each patient, depending on their tumor and lifestyle.
Hopes that physical activity may one day have an effect on the tumor are not entirely unfounded. But for now, what has been proven is that physical activity sufficiently regular and well-balanced improves the patient's quality of life, improves their overall health, reduces the side effects of treatments, and enhances the effects of certain treatments. That's already a lot.
Gregory NinotProfessor of Health, Psychology, and Sports Science, University of Montpellier
The original version of this article was published on The Conversation.