On Jun. 2, 2025, 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.

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.

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.