Physical activity has long been recommended for many people recovering from cancer treatment because it can help preserve strength, fitness, and quality of life. In 2025, the CHALLENGE trial added an important new finding. Among patients who had completed surgery and chemotherapy for colon cancer, a three-year structured exercise programme led to a longer period without recurrence, a new primary cancer, or death.
This does not mean exercise can treat cancer on its own or replace standard therapy. The trial studied exercise as an additional part of recovery after treatment—and only in a clearly defined group of patients.
Who and what did the researchers study?
The international randomised trial included 889 people with stage III or high-risk stage II colon cancer. Every participant had undergone surgery and completed adjuvant chemotherapy.
They were then randomly assigned to two groups:
- 445 participants followed a structured physical-activity programme for three years;
- 444 participants received health and physical-activity education materials without the same long-term personalised support.
This distinction matters. The researchers did not compare “exercise” with complete inactivity; they compared a structured programme with a less intensive educational intervention.
What were the results?
-
At 5 years without recurrence, a new primary cancer, or death
80.3% in the exercise-programme group and 73.9% in the control group -
Alive at 8 years
An estimated 90.3% versus 83.2% -
Participants
889 patients who had completed surgery and adjuvant chemotherapy
The difference in the five-year measure was 6.4 percentage points, while the difference in estimated eight-year survival was 7.1 percentage points in favour of the structured exercise group.
What do these figures mean?
Five-year disease-free survival did not refer only to the cancer returning. The trial counted three possible events: recurrence of colon cancer, development of a new primary cancer, or death from any cause. At five years, an estimated 80.3% of the exercise group and 73.9% of the control group had experienced none of these events.
Eight-year overall survival is a clinical statistical term. In plain language, it is the estimated proportion of participants who were alive at eight years, regardless of whether their cancer had returned or what the cause of death might have been.
This is a group estimate, not an individual prediction
These percentages cannot predict what will happen to a particular patient. Outcomes are also shaped by tumour characteristics, age, other medical conditions, treatment, and many additional factors.
What did the exercise programme involve?
Participants were not simply told to “move more.” They had regular contact with physical-activity consultants, received personalised goals, and gradually increased mainly aerobic exercise. Some sessions were supervised, and behavioural support continued throughout the three-year programme.
The initial goal was to add approximately 10 MET-hours of activity per week above each participant’s usual level during the first six months and then maintain that increase. As a rough illustration, this is equivalent to about 2.5 hours of brisk walking per week, although participants could choose other forms of aerobic activity.
What is a MET-hour?
A MET is a unit used to combine the intensity and duration of physical activity. Most readers do not need to calculate MET-hours in daily life. In this trial, the measure helped researchers set comparable goals for people starting from different fitness levels.
For that reason, the CHALLENGE findings should not be reduced to the advice “just walk more.” The intervention was long-term, tailored to the individual, and supported by trained staff.
What kinds of activity may be suitable after treatment?
The programme focused mainly on aerobic exercise. Depending on a person’s health and recovery, possible options may include:
- walking at a comfortable or brisk pace;
- using a stationary bike or cycling gently;
- using an elliptical trainer;
- swimming when approved by the medical team;
- gradually returning to other familiar activities.
The American Cancer Society advises cancer survivors to gradually work towards 150–300 minutes of moderate-intensity or 75–150 minutes of vigorous-intensity activity each week and, where appropriate, to include strength training. This is a general guideline, however, not the exact CHALLENGE protocol.
Why is a gradual start important?
Muscle, joint, and other musculoskeletal problems were reported more often in the structured exercise group: 18.5% of participants compared with 11.5% in the control group.
After surgery and chemotherapy, peripheral neuropathy, a stoma, anaemia, severe fatigue, heart problems, joint pain, or the effects of surgery may all change which activities are appropriate. A programme that is safe for one person may not be suitable for another.
For someone who has never exercised
A first goal might be a short walk or a few minutes of another manageable activity, followed by a gradual increase. Consistency and tolerance matter more than trying to reach the maximum recommendation immediately.
What the trial does not prove
- It does not show that exercise can replace surgery, chemotherapy, or any other cancer treatment.
- The findings cannot automatically be applied to every cancer, rectal cancer, metastatic disease, or exercise during active treatment.
- The trial did not identify one form of exercise that is best for everyone.
- It did not conclusively establish the biological mechanism responsible for the outcome.
Researchers are considering several possible explanations, including changes in insulin sensitivity, systemic inflammation, body composition, physical fitness, and immune signalling. CHALLENGE, however, primarily tested the clinical effect of the programme rather than proving the role of any single mechanism.
The main conclusion
CHALLENGE was the first large randomised trial in which a long-term structured exercise programme after standard colon cancer treatment improved the time participants lived without recurrence, a new primary cancer, or death. The findings were also consistent with longer overall survival in this specific patient group.
The practical message is not that patients should copy someone else’s exercise plan. Physical activity is better understood as a meaningful part of recovery that can be built gradually and safely with support from the medical team.
