“Most studies on how exercise affects the survival of people with cancer have been observational. A clinical trial provides compelling evidence of the benefits of physical activity.
Owing to advances in medical treatment, many people with cancer are living longer1. However, these individuals remain at risk of their cancer recurring, or arising at other locations in the body, and they might also be vulnerable to developing other health conditions (termed comorbidities). There is therefore a growing need to investigate whether modifiable lifestyle factors can improve health and survival in this population. Writing in The New England Journal of Medicine, Courneya et al.2 present the results of a clinical trial assessing the effects of a structured exercise programme of supervised physical activity on people who had been treated for colon cancer.
Previous research into how exercise can help people with cancer to live longer and healthier lives has tended to take the form of observational studies (which collect data without intervening to change any variables), the results of which might be biased owing to methodological challenges3. Randomized controlled trials (RCTs) can provide data that are more robust than are those from observational studies. However, such RCTs are usually small-scale studies that focus on changes in lifestyle, body weight or quality of life as outcomes4. Although the results of these studies are promising — for example, they suggest that physical activity improves survival and quality of life in people who have had colorectal cancer3 — evidence from large, high-quality RCTs that assess the effects of exercise on key clinical outcomes, such as cancer recurrence, new cancer or death, has been lacking. Courneya and colleagues’ findings constitute a major step forward, providing evidence that exercise can notably improve the health and survival of some people who have been treated for cancer.
The clinical trial examined how a three-year structured programme of moderate-to-vigorous physical activity affected disease-free survival (survival without signs of the cancer returning) in people who had been treated for colon cancer. A total of 889 study participants — all of whom had undergone tumour-removal surgery and chemotherapy after being diagnosed with stage III or high-risk stage II colon cancer — were randomly assigned to one of two groups. Those in the first group (445 individuals) were enrolled in an exercise programme, which included exercise sessions — some mandatory and some just recommended — under the supervision of a trained physical-activity consultant, as well as compulsory behavioural-support sessions aiming to help them to change their behaviour with regard to exercising. They also received health-education materials promoting healthy nutrition and physical activity. Those allocated to the second group (444 individuals) received the health-education materials only. The two treatment groups had similar demographic and clinical characteristics, and only a few individuals withdrew from the study or were lost to follow-up (meaning that although they were enrolled and potentially able to participate, they did not do so for various reasons), which enabled a fair comparison to be made between the groups.
After a median follow-up period of around eight years, disease-associated events (defined as cancer recurrence, a new unrelated primary cancer or death) had occurred in 224 participants, and 107 individuals had died from any cause. Both disease-free survival and overall survival were significantly longer in the exercise group than in the group that received health-education materials only.
To meet a predefined threshold of statistical significance for the trial, Courneya et al. had aimed to capture a total of 380 events of disease recurrence, new primary cancer or death. Although only 224 were detected, the results of the study were still clinically meaningful, partly because the beneficial effects of exercise on survival outcomes were stronger than predicted. The exercise group reported more adverse musculoskeletal events than did the health-education group, but just 10% of these events were thought to be related to the exercise programme, and they could be managed through individualized exercise plans.
Exercise in general has been shown to have many positive effects for people who have had cancer5. Individuals who seek to improve their overall health and survival outcomes are encouraged by health professionals to exercise, if they are able to. The participants in the trial were already undertaking exercise at some level at the time of recruitment, and the structured exercise programme was designed to help those in the exercise group to increase their baseline levels of physical activity and to reach specific exercise goals in phases over three years. Attendance was lower at the recommended exercise sessions than it was at the mandatory ones, and participation also declined over time. This highlights the challenges of maintaining an exercise routine and the need for support from trained individuals to help people to build practical and sustainable exercise regimens.
The increase in physical activity in the exercise group was equivalent to adding about 45–60 minutes of brisk walking, or 25–30 minutes of jogging, three or four times per week. This is in line with current guidelines for people who have cancer, which recommend 150–300 minutes of moderate-intensity or 75–150 minutes of vigorous-intensity exercise per week, or a combination of these6. Activities including aerobic exercise (such as brisk walking, cycling or swimming) and muscle-strengthening exercises (for example, weight-lifting, body-weight exercises or carrying heavy shopping) can all be considered.
The trial has some noteworthy limitations. Both the exercise and the health-education group reported increased levels of moderate-to-vigorous physical activity, accompanied by improvements in physical functioning and cardiorespiratory fitness. Although the exercise group achieved and maintained greater improvements than the health-education group did throughout the intervention period, the gains reported in the health-education group reduced the difference between the groups, leading to an underestimation of the effects of exercise. Furthermore, the authors note that the trial might have included individuals with higher than average physical functioning and excluded people whose disease recurred during the first year after diagnosis. Therefore, the findings might apply only to this selected group of people recovering from colon cancer.
Understanding the biological mechanisms that drive the beneficial effects of exercise could help to inform future treatment strategies. How exercise improves survival for people with colon and other types of cancer remains poorly understood, although reduced inflammation and improved immune function and metabolic health are plausible underlying mechanisms7. Notably, there was no reduction in body weight or waist circumference in the exercise group; however, moderately vigorous exercise might preserve muscle mass in people with cancer, which has been linked to an improved prognosis7.
This landmark study by Courneya and colleagues demonstrates a strong beneficial effect of structured exercise on health outcomes for people treated for colon cancer, and is likely to influence clinical guidelines and care practices. However, whether supervised, structured exercise interventions can be implemented routinely, as a core aspect of post-treatment care in health systems that are currently overwhelmed, remains a key question for policymakers. Encouragingly, another key finding from the trial was a reduction in new primary cancers (particularly breast cancer) in the exercise group, which further supports the benefits of physical activity for cancer prevention.
The lack of evidence from RCTs — as well as the premature withdrawal of funding in a previous exercise-intervention trial8 — has made it hard to generate robust conclusions about the role of exercise during and after treatment in the diverse population of people with cancer who have a variety of physical capabilities. The encouraging results of this clinical trial should bolster efforts to expand research in this area and motivate further studies examining whether similar interventions could be effective for other types of cancer.” [A]
A. Nature 645, 866-867 (2025) Doris S. M. Chan & Marc J. Gunter
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