A first-of-its-kind international trial provides definitive evidence that people who follow a structured exercise program after surgery and chemotherapy for colon cancer have a lower risk of their cancer coming back and better odds of survival.
"Our study shows that exercise is no longer just a quality-of-life intervention for cancer patients that can be offered when and where possible. It is a treatment for colon cancer that must be made available to all patients," says Kerry Courneya, professor in the Faculty of Kinesiology, Sport, and Recreation and Canada Research Chair in Physical Activity and Cancer, who was co-lead on the Canadian Cancer Trials Group CO.21 (CHALLENGE) trial.
As Courneya explains, previous studies exploring exercise's effect on cancer outcomes have been observational — researchers simply followed patients over time, with the aim of seeing if exercise is associated with improved survival. Such studies have fundamental flaws. The CHALLENGE trial is a randomized controlled Phase 3 trial, which is "the definitive test of whether or not something improves a health outcome," says Courneya.
"It's the same study design they use to test new drugs for cancer. It's the absolute best evidence we have that a treatment works."
Between 2009 and 2024, 889 patients with Stage 3 or high-risk Stage 2 colon cancer were enrolled in the trial. After undergoing surgery and completing their chemotherapy, half of the patients were randomly assigned to participate in a structured exercise program involving moderate-intensity aerobic activities like walking, biking or exercising on an elliptical, while the other half were given the standard care, which involved receiving educational materials promoting physical activity and healthy eating. Both groups were given the same followup care and ongoing cancer surveillance. Medical oncologist and study co-author Neil Chua was involved in recruiting patients and conducting followups.
"Much to our excitement, we showed that the patients randomized to the exercise group had improved disease-free survival, which includes lower risk of recurrence of the cancer, lower risk of a new secondary cancer, and a lower risk of death," says Courneya.
Five years on, patients in the structured exercise group had an 80 per cent disease-free survival rate, compared with 74 per cent in the health education materials group, as well as a 28 per cent lower risk of recurrence or new cancers. At eight years, patients in the exercise group had a 37 per cent lower risk of death, with a 90 per cent overall survival rate compared to 83 per cent in the health education group.
Structure and support needed for patients
The guidance provided by the structured exercise program was integral to the efficacy of exercise as an intervention, says Courneya.
"Recommending exercise to cancer patients is no more helpful than recommending chemotherapy. We must provide patients with the support they need to successfully complete the exercise programs we recommend."
Those in the structured exercise program group met with a physical activity consultant — typically a kinesiologist or physiotherapist — twice monthly in the initial 12 months, and then monthly over the next two years.
"The structured exercise program was designed based on key behaviour change principles. It didn't just instruct participants on what to do; it helped them understand how to realistically incorporate it into their lives using evidence-based strategies and built-in accountability," says Fernanda Arthuso, a postdoctoral fellow in the Exercise Oncology Research Laboratory that Courneya leads.
Arthuso was the physical activity consultant who met with Edmonton-area patients in the study, guiding them through their exercise programs, and also served as a research assistant.
"Exercise specialists can provide personalized guidance that helps colon cancer survivors maximize the benefits of physical activity in a safe and effective way," she says. "They can also help survivors navigate common barriers, making it easier for them to stay motivated and engaged over time."
Colorectal cancer is the second leading cause of cancer-related deaths worldwide. According to the study authors, patients with high-risk Stage 2 and Stage 3 colon cancer have a 30 per cent risk of cancer recurrence. And, as Courneya adds, the cancer can be even harder to treat after a recurrence, making it essential to identify strategies to prevent recurrence.
Next, researchers plan to analyze blood samples from CHALLENGE trial participants to begin identifying some of the mechanisms contributing to the exercise intervention's efficacy.
"We'll be able to look at whether the exercise intervention caused changes in things like insulin, natural killer cell activity, T-cell activity, and those types of things," says Courneya.
An integral part of cancer care
He also highlights that it's imperative for exercise interventions to become integrated into cancer care the same way other treatments are.
"Most cancer centres are set up to deliver drugs like immunotherapy or chemotherapy, to deliver radiotherapy. They're not really set up to deliver these lifestyle interventions."
For patients to truly benefit from the power of an exercise intervention, exercise specialists need to be considered a key part of the care team, just like the health-care professionals delivering other treatments.
And though it's tough to generalize as to whether a structured exercise program would be just as beneficial for patients with other types or stages of cancer, Courneya says a good place to start is to consider observational studies in which patients responded well to exercise intervention, or to look at patients in a similar treatment scenario, after surgical removal of the primary tumour and after chemotherapy.
"Wider applicability is the million-dollar question many oncologists and patients will want to know, and while it's a tricky one, perhaps the CHALLENGE trial shows that maybe in those scenarios we can expect the same benefits of exercise."
