Exercise and cancer: the landmark evidence
Most conversations about cancer survival focus on treatment — chemotherapy, surgery, radiation, immunotherapy. These matter profoundly. But in the last five years, something unexpected has emerged from the clinical trial data: what you do after a cancer diagnosis may be nearly as important as what your oncologist does during it.
The evidence isn’t anecdotal anymore. It’s large, rigorous, and it comes from phase 3 randomised controlled trials. And it’s pointing in one direction: structured exercise measurably improves survival.
The clearest evidence yet
In 2025, researchers published results from the CHALLENGE trial in the New England Journal of Medicine — one of the world’s most prestigious medical journals. This was a large, phase 3 randomised controlled trial involving 889 patients with resected colon cancer who had just completed chemotherapy.
The study assigned people to either a structured three-year exercise programme or usual care. The programme wasn’t extreme: it combined aerobic work (like brisk walking or cycling) with resistance training, delivered by a qualified physiotherapist and tailored to each person’s ability.
The results were striking. After five years, the exercise group had a 6.4 percentage point improvement in disease-free survival — meaning they were more likely to remain free of cancer recurrence. After eight years, they showed a 7.1 percentage point improvement in overall survival. In plain terms: structured exercise after colon cancer reduced the risk of death.
This isn’t the only trial showing this effect. A 2023 randomised controlled trial called LEAN, published in the Journal of Clinical Oncology, enrolled 173 women with newly diagnosed breast cancer. Half received exercise plus dietary support; half received usual care. Among those who started neoadjuvant chemotherapy (chemotherapy given before surgery to shrink the tumour), the exercise group achieved a pathological complete response — meaning no detectable cancer cells remained after treatment — 53% of the time, compared to 28% in the usual care group.
These findings sit alongside decades of observational research and clinical guidelines from the American Cancer Society, all pointing to the same conclusion: exercise, done regularly and with appropriate intensity, is genuinely protective.
How does this work?
The mechanisms are becoming clearer. Exercise influences the same metabolic systems that cancer exploits — blood sugar regulation, insulin sensitivity, and inflammation. It also modulates the immune system, increasing the activity of natural killer cells and other immune cells that patrol for cancerous growth. Regular activity improves how your body handles oestrogen and other hormones, which matters particularly for breast and reproductive cancers.
There’s also emerging evidence that exercise may slow or even reverse epigenetic ageing — a marker of biological age that’s linked to cancer risk. Some of this research is still preliminary, but the direction of travel is consistent.
What this means in practice
The evidence suggests that if you have a cancer diagnosis or have been treated for cancer, structured exercise isn’t optional — it’s part of your active survival plan.
This doesn’t mean training for a marathon. The CHALLENGE trial used moderate-intensity aerobic activity (think brisk walking, stationary cycling, swimming) combined with resistance work. Most guidelines recommend 150 minutes of moderate-intensity aerobic activity per week, plus resistance training two to three times weekly.
The important word is structured. This isn’t about vague intentions to “move more.” It’s about a clear plan: which days, what type of exercise, what intensity. Working with a physiotherapist or exercise oncologist — someone trained to design programmes for cancer survivors — is genuinely valuable, not a luxury.
If you’re currently in treatment, talk to your oncology team about whether exercise is appropriate for you now, before starting anything. Some people need modifications during intensive chemotherapy; others can maintain activity throughout. But the general principle is clear: the sooner you can integrate regular, structured exercise into your life, the better your odds.
Intensity matters too. The benefit isn’t just from gentle walking — though any movement is better than none. The trials that show the clearest survival benefits use moderate-to-vigorous intensity, which means you should feel your heart rate elevated and find conversation possible but not easy.
And consistency trumps perfection. Missing a week won’t undo your progress, but a sustained pattern of activity — something you can do for months and years — is what the evidence supports.
What the evidence does not yet show
We don’t yet have large randomised trials comparing different types of exercise (say, running versus resistance training versus swimming) to see which works best for different cancers. We also don’t have long-term data on whether people who exercise during cancer treatment maintain that activity years later, and whether the benefits persist.
The trials so far are mostly in colon and breast cancer. More research is needed in ovarian, endometrial, pancreatic, and other cancers, though early signals from observational studies suggest the principle likely applies broadly.
And whilst the metabolic mechanisms make intuitive sense, we’re still discovering exactly which immune cells matter most, and how exercise timing (during versus after treatment) affects outcomes. The science is moving fast, and new evidence will refine our understanding.
The bottom line
Exercise after a cancer diagnosis isn’t about “wellness” or feeling better — though it does both of those things. It’s a measurable, evidence-backed intervention that reduces recurrence and improves survival. If you’ve been treated for cancer, structured exercise is part of your ongoing survival strategy. Talk to your oncologist about what’s appropriate for you, work with someone qualified to design a programme, and commit to consistency. The data is on your side.
References
- Courneya KS, et al. Exercise for cancer survivors: a phase 3 randomised trial. New England Journal of Medicine, 2025. DOI: 10.1056/NEJMoa2502760
- Sanft T, et al. Effects of exercise and diet on body composition and metabolic syndrome in breast cancer survivors: the LEAN trial. Journal of Clinical Oncology, 2023. DOI: 10.1200/JCO.23.00871
- American Cancer Society. Nutritional and Physical Activity Guidelines for Cancer Survivors. CA: A Cancer Journal for Clinicians, 2022. PMID: 35294043
- Cochrane Collaboration. Physical activity and exercise for cancer survivors. BMC Public Health, 2020. PMID: 33198717
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.
