The CHALLENGE trial in detail: what a 3-year exercise programme achieved in colon cancer
In May 2025, the New England Journal of Medicine published what is arguably the most important exercise and cancer trial ever conducted. The CHALLENGE trial — a phase 3 randomised controlled trial of structured exercise in patients with resected colon cancer — reported results that the oncology community had been waiting decades for: clear, statistically significant evidence that a sustained exercise programme after cancer treatment improves long-term survival outcomes.
This post goes inside the trial. What the programme actually looked like, who it enrolled, what the participants did for three years, and what the data showed — including the figures that matter most for anyone living with or beyond a colon cancer diagnosis.
Background: why colon cancer and why exercise
Colon cancer is one of the cancers with the longest-standing observational evidence linking physical activity to prognosis. Prospective cohort studies had consistently found that higher physical activity levels after diagnosis were associated with better disease-free survival and overall survival. The biological rationale was coherent: exercise reduces insulin and IGF-1, lowers systemic inflammation, improves immune surveillance, and shifts the metabolic environment in ways that may impair residual tumour cell survival.
But observational evidence has a fundamental limitation — people who exercise after a cancer diagnosis may differ from those who do not in multiple ways that affect survival independently of exercise. To move from association to causation, a randomised controlled trial was needed. CHALLENGE was that trial.
Trial design
The CHALLENGE trial enrolled 889 patients with stage II or III colon cancer who had completed standard adjuvant chemotherapy within the preceding two to six months. Participants were randomised to either a structured exercise programme or a health education control group.
The exercise programme ran for three years — a duration that reflects the serious ambition of the trial and that distinguishes it from most exercise intervention studies, which run for weeks or months. The programme was delivered by exercise specialists through a combination of in-person sessions and telephone-based support, with participants exercising independently at home for the majority of the programme duration.
The control group received a structured health education programme of equivalent contact time — an important design feature that prevents any detected benefit being attributable simply to additional professional contact or motivation, rather than the exercise itself.
What the exercise programme involved
The exercise prescription was aerobic-focused, based on progressive intensity and volume over the three-year period. In the early months, participants worked at moderate intensity, gradually increasing towards vigorous intensity as fitness improved. The target was approximately 150 minutes of moderate-intensity aerobic exercise per week, with the option to progress to higher volumes for those able to tolerate it.
Exercise modalities were flexible — walking, cycling, swimming, and other aerobic activities were all permitted, reflecting the real-world need for an intervention that people can sustain over years. The emphasis was on consistency and progressive challenge rather than any specific exercise form.
What the trial found
The primary outcome was disease-free survival at five years. The secondary outcome was overall survival at eight years.
Five-year disease-free survival: 72.4% in the exercise group versus 66.0% in the control group — a 6.4 percentage point difference. This was statistically significant and clinically meaningful: for every 16 patients who completed the exercise programme, approximately one additional patient was alive and recurrence-free at five years who would not otherwise have been.
Eight-year overall survival: 78.4% in the exercise group versus 71.3% in the control group — a 7.1 percentage point difference. The survival benefit was not only real at five years but persisted and widened at eight years.
These are not marginal findings. A 7.1 percentage point improvement in eight-year overall survival from a lifestyle intervention — delivered without pharmaceutical side effects, at relatively low cost, and with a range of additional health benefits — is a result that warrants serious attention from oncologists, patients, and anyone concerned with cancer survivorship.
Why the effect size matters
To contextualise the CHALLENGE findings: many adjuvant chemotherapy regimens in stage III colon cancer produce overall survival improvements in the range of 3–7 percentage points compared to surgery alone. The CHALLENGE exercise programme, added on top of standard chemotherapy, produced a comparable magnitude of benefit. This does not mean exercise replaces chemotherapy — it does not — but it does suggest that exercise is not a peripheral wellbeing measure. It is a treatment-level intervention in colon cancer survivorship.
The biological mechanisms
Chronically elevated insulin and IGF-1 — associated with physical inactivity, excess body fat, and the metabolic disruption of cancer treatment — activate signalling pathways in residual cancer cells that promote survival and proliferation. Exercise durably lowers fasting insulin and improves insulin sensitivity, removing this survival signal from any remaining cancer cells.
Systemic inflammation, mediated by IL-6, TNF-α, and other pro-inflammatory cytokines, creates a microenvironment that supports cancer cell persistence. Chronic aerobic exercise consistently reduces circulating inflammatory markers in cancer survivors. Natural killer cell activity and cytotoxic T-cell function — the immune system’s primary tools for identifying and destroying residual cancer cells — are also enhanced by regular aerobic exercise.
What the evidence does not show
The CHALLENGE trial enrolled patients with resected stage II and III colon cancer who had completed adjuvant chemotherapy. Whether the same magnitude of benefit applies to other cancer types, to patients who did not receive chemotherapy, or to patients at different disease stages is not established by this trial.
The trial also cannot tell us how much of the benefit came from the exercise itself versus the increased professional contact, motivation, and behavioural structure that the programme provided. And whilst the programme ran for three years, the trial does not tell us whether lifelong exercise maintenance is necessary to preserve the survival benefit.
What this means in practice
For colon cancer survivors specifically, the evidence is now strong enough to regard exercise as a component of standard care. The CHALLENGE trial is phase 3 randomised evidence — the highest tier of clinical evidence — showing that a structured aerobic exercise programme begun after adjuvant chemotherapy improves both disease-free and overall survival at clinically meaningful magnitudes.
The programme is achievable. The CHALLENGE exercise prescription — approximately 150 minutes of moderate aerobic activity per week, progressing in intensity over time — is not an elite athlete’s programme. It is a commitment that most people recovering from colon cancer treatment can work towards, with appropriate professional support.
Starting matters more than perfection. The CHALLENGE programme was designed for progressive uptake — participants built towards targets over months, not weeks. Working with an oncology physiotherapist or exercise specialist to design an individualised progressive programme is more effective than waiting until you feel well enough to start.
The benefit compounds over time. The widening of the survival difference between five and eight years suggests that the benefit of exercise may accumulate rather than plateau. Sustained, long-term exercise engagement — not a short-term burst followed by a return to inactivity — is what the evidence supports.
The bottom line
The CHALLENGE trial is the strongest evidence yet that exercise is not merely supportive care for colon cancer survivors — it is an intervention that meaningfully extends life. A 3-year structured aerobic exercise programme produced a 6.4 percentage point improvement in five-year disease-free survival and a 7.1 percentage point improvement in eight-year overall survival in patients with resected stage II and III colon cancer. These are treatment-level effect sizes from a lifestyle intervention. For anyone living with or beyond colon cancer, the message from this trial is clear: structured, sustained aerobic exercise is one of the most evidence-supported things you can do.
Scientific references
- Courneya KS, et al. CHALLENGE trial: exercise and colon cancer survival. New England Journal of Medicine. 2025. DOI: 10.1056/NEJMoa2502760
- Patel AV, et al. American Cancer Society guideline for diet and physical activity for cancer prevention. CA: A Cancer Journal for Clinicians. 2020;70(4):245–271. DOI: 10.3322/caac.21591
- Rock CL, et al. American Cancer Society guideline for diet and physical activity for cancer survivors. CA: A Cancer Journal for Clinicians. 2022. PMID: 35294043
This article is written for educational and informational purposes only. It is not intended as medical advice and should not be used to diagnose, treat, prevent, or cure any medical condition, including cancer. If you have a cancer diagnosis or are undergoing treatment, please discuss any lifestyle or dietary changes with your oncologist or medical team before making them. The studies cited reflect current research at the time of writing; the field is evolving rapidly and findings may be updated or superseded. Chloe Archard is a nutritional health coach, not a medical doctor.
