In mid-2025 a trial called CHALLENGE was published in the New England Journal of Medicine, and for about two weeks the internet decided exercise cures cancer.
The result is genuinely important. It is also more specific, and more demanding, than nearly any coverage of it suggested — and the specifics are what make it useful to you.
What was actually done
889 patients with stage III or high-risk stage II colon cancer, who had already had surgery and completed adjuvant chemotherapy, were randomised to one of two groups. One received health-education materials. The other entered a structured exercise program.
The goal was to increase recreational physical activity by at least 10 MET-hours per week above baseline — roughly two and a half hours of brisk walking, or less time at higher intensity.
Here is the part that matters and that almost nobody reports: participants met with an exercise specialist every two weeks for the first year, then monthly for two more years. This was a three-year, individualised, supervised behaviour-change program with a human being attached to it. It was not a pamphlet saying “try to walk more.”
Median follow-up was 7.9 years.
What was found
Disease-free survival at five years: 80% in the exercise group versus 74% in the health-education group. Hazard ratio 0.72 (95% CI 0.55–0.94), P = 0.02. That was the trial’s primary endpoint, and it was met.
Overall survival at eight years: 90% versus 83%. Hazard ratio 0.63 (95% CI 0.43–0.94).
Worth noting how carefully the authors worded that second one. Overall survival was a secondary endpoint, and the paper says results “support longer overall survival in the exercise group” — not that survival was significantly longer, which is the phrasing used for the primary endpoint. No P value is reported for it. That restraint is a mark of a well-run trial, and it is a distinction most coverage flattened.
Still: these are real numbers from a well-conducted randomised trial with nearly eight years of follow-up. In a field where most positive findings are small, soft, or do not replicate, this one is solid.
The three things the headlines dropped
1. The intervention was coaching, not exercise. This distinction is the whole thing. What was tested was three years of structured, supervised, individually tailored behaviour support. Telling someone to exercise more is a well-studied intervention and it mostly does not work. What worked here was the scaffolding.
2. It applies to colon cancer, after chemotherapy. Stage III or high-risk stage II, post-surgery, post-adjuvant chemo. It says nothing about exercise during treatment, and nothing about breast, prostate, lung or any other cancer. Exercise is well supported for symptoms across cancer types. Exercise improving survival has been shown here, in this population.
3. It caused some harm. Musculoskeletal adverse events of any grade: 18.5% in the exercise group versus 11.5% in the education group. About one in ten of those were judged program-related. Mild, expected, worth naming — a trial that reports its harms honestly is a trial you can trust on its benefits.
What is well established, separately from this trial
You do not need CHALLENGE to justify exercising after cancer treatment. The case was already made.
The SIO–ASCO 2024 guideline on cancer-related fatigue — built on 113 randomised trials — gives exercise a strong recommendation for reducing fatigue, both during treatment and after it ends. Only two other interventions carry a strong recommendation in both settings: cognitive behavioural therapy and mindfulness-based programs. (Tai chi and qigong also earn a strong recommendation, but during treatment only.)
The American Cancer Society’s survivor guideline sets the target at 150–300 minutes per week of moderate-intensity activity — where you can talk but not sing — or 75–150 minutes of vigorous activity, plus muscle-strengthening on two or more days a week.
The American College of Sports Medicine’s roundtable gets more specific. For fatigue: aerobic activity at about 65% of maximum heart rate, 30 minutes, three times weekly for twelve weeks. Or resistance training at 60% of one-rep max, 12–15 reps, two sets, twice weekly for twelve weeks.
If you are reading this two weeks out of chemotherapy
Those numbers are a destination, not a starting line, and reading them while exhausted is discouraging rather than motivating.
Start with what is actually available today. If that is a walk to the end of the driveway, that is the program. Add a little each week. The trial that produced those survival numbers ran for three years — nobody in it started at the target either.
The other honest note: the thing that separated the two groups in CHALLENGE was not knowledge, it was structure. Both groups were told exercise matters. One group had someone checking in every two weeks for a year. If you can build some version of that — a physical therapist, a trainer who understands cancer recovery, a friend who walks with you on a schedule — you are at least borrowing the shape of what was tested. Whether that reproduces the trial’s survival results is not something anyone can tell you, and nobody should.
This article is educational and is not medical advice. Talk to your oncology team before starting an exercise program, particularly if you have bone metastases, low blood counts, or a central line. Venturis Clinic is not a cancer treatment center and does not treat cancer.
Written by Dr. Alvin Philipose, B.S., B.S., DC, ICCP
Reviewed 20 August 2026
