The Trial That Changed the Conversation

The turning point came in June 2025, when results from the CHALLENGE trial were presented at the American Society of Clinical Oncology’s annual meeting and published in The New England Journal of Medicine. Researchers enrolled 889 patients who had completed surgery and chemotherapy for stage 3 or high-risk stage 2 colon cancer. About 90% had stage 3 disease, according to a CancerNetwork review of the trial.

Patients were randomly assigned to a structured exercise program or to health education materials, which the University of Sydney release described as the current standard of care. The exercise program lasted three years and included regular meetings with a fitness coach, according to Associated Press reporting summarized by HealthDay. Participants were not already meeting the recommended 150 minutes of moderate activity a week when they joined.

The hazard ratio for recurrence, new primary cancer or death was 0.72, a 28% reduction, with a median follow-up of 7.9 years, according to CancerNetwork. Overall survival improved by 37%. “Now we can say definitively exercise causes improvements in survival,” study co-author Kerry Courneya of the University of Alberta told the Associated Press, as reported by HealthDay. Dr. Jeffrey Meyerhardt of Dana-Farber Cancer Institute said it was the first randomized controlled trial to show fewer recurrences and better survival with exercise.

Why a Randomized Trial Matters So Much

Before CHALLENGE, nearly all evidence that exercise helped cancer survival came from observational studies, which compare active and inactive people. Those studies cannot rule out that healthier people simply exercise more. A randomized trial assigns the exercise by chance, so differences in outcome can be attributed to the program itself. That is the same standard used to approve cancer drugs, which is why oncologists describe the result as practice-changing rather than merely encouraging.

How Exercise Moved From Advice to Guideline

The trial did not arrive out of nowhere. In 2019, an American College of Sports Medicine roundtable of 40 experts reviewed the research and concluded that physical activity is linked to lower risk of seven common cancers: colon, breast, kidney, endometrial, bladder, stomach and esophageal adenocarcinoma, according to the National Institutes of Health director’s blog. The panel also found exercise before and after diagnosis was linked to better survival in breast, colorectal and prostate cancers.

1. 2010First ACSM expert panel on exercise and cancer
2. 20161.44 million-person study links activity to 13 cancers
3. 2019ACSM roundtable of 40 experts sets survivor dosing
4. 2022ASCO guideline backs exercise during treatment
5. 2025CHALLENGE trial shows 37% lower risk of death
6. 2026ACS projects 2.1 million new U.S. cases

In May 2022, the American Society of Clinical Oncology published its first guideline focused on people actively receiving treatment. It states that oncology providers should recommend regular aerobic and resistance exercise during active treatment with curative intent, and may recommend exercise before surgery for lung cancer. Preoperative exercise in lung cancer patients reduced hospital stay and complications, the guideline found.

The ASCO panel was careful about limits. Evidence was not sufficient to recommend exercise during treatment specifically to improve recurrence, survival or treatment completion, the guideline notes. Its case rests on how people feel and function: exercise reduces fatigue, preserves cardiorespiratory fitness, physical functioning and strength, and in some groups improves quality of life and reduces anxiety and depression, with low risk of adverse events. More than 100 clinical trials have examined exercise during treatment, lead author Jennifer Ligibel told Healio.

The scale explains the urgency. The American Cancer Society projects 2,114,850 new cancer cases and 626,140 cancer deaths in the United States in 2026, about 5,800 diagnoses a day. Five-year relative survival across all cancers has reached 70%, which means a growing population of survivors living with the long-term effects of treatment, from fatigue to heart strain to muscle loss. Exercise addresses many of those at once.

The Prevention Side: Lower Risk Across 13 Cancers

Exercise does not only matter after a diagnosis. A 2016 study in JAMA Internal Medicine, led by Steven Moore of the National Cancer Institute, pooled data from 12 U.S. and European studies with 1.44 million people. Compared with the least active, the most active had lower risk of 13 of 26 cancer types studied and a 7% lower risk of cancer overall, as reported by Pharmacy Times.

Most of these links held regardless of body weight or smoking history, the researchers reported. There were two exceptions in the other direction: higher activity was associated with a 5% higher risk of prostate cancer, which researchers thought might reflect more screening among active men, and higher melanoma risk, likely from more sun exposure. Because the activity data were self-reported and observational, the study shows association, not proof that exercise prevents each cancer.

Why Moving Muscles May Affect Tumors

Scientists do not yet know exactly how exercise fights cancer, and several mechanisms likely work together. Exercise improves how the body handles insulin, which matters because cancer cells may use insulin to grow and divide faster, Scientific American reported. During exercise, immune cells called natural killer cells and T cells increase significantly in number. Muscles also release signaling proteins called myokines that researchers are studying for possible anti-tumor effects.

How Much Exercise Do Cancer Patients Need?

The 2019 ACSM roundtable translated the evidence into specific prescriptions. For cancer survivors, moderate aerobic and resistance exercise at least three times a week, for about 30 minutes per session, for at least 8 to 12 weeks may consistently improve common treatment-related symptoms and side effects, according to the roundtable’s executive summary. The dose depends on the problem being targeted.

For cancer prevention, ACSM points to the federal Physical Activity Guidelines: 150 to 300 minutes a week of moderate activity or 75 to 150 minutes of vigorous activity. For survival, the exact dose needed to reduce cancer-specific or overall death is not yet known, though more activity appears to bring greater benefit, according to the same guidance.

Doses are drawn from ACSM’s 2019 exercise guidelines for cancer survivors; weekly minutes are calculated by this desk. ACSM also lists resistance and combined aerobic plus strength options, typically two strength sessions a week of 2 sets of 8 to 15 repetitions. Your care team may adjust any dose for your diagnosis, treatment and fitness. People with or at risk of lymphedema should take extra care with strength training, such as wearing a compression sleeve, according to the Society of Behavioral Medicine.

Getting Started Safely During or After Treatment

The CHALLENGE results came from a supported program with coaching, not a printed handout. That detail matters. People who start on their own often stop when fatigue or setbacks hit. Asking for a referral to an exercise professional who understands cancer can make the difference between a plan that lasts three weeks and one that lasts three years.

1. Ask your oncologist firstConfirm any limits tied to surgery, bone involvement, blood counts or heart effects.
2. Request a referralPhysical therapists, exercise physiologists and cancer rehab programs can tailor a plan.
3. Start with 10 minutesShort walks count; build toward 30 minutes, 3 times a week.
4. Add strength twice a weekTwo sets of 8 to 15 reps for major muscle groups.
5. Adjust on hard daysLower intensity during treatment cycles rather than stopping entirely.
6. Track and reportNote fatigue, mood and sleep; share changes with your care team.

When to Pause or Check In

Stop and contact your care team if you have chest pain, unusual shortness of breath, fainting, new bone pain, fever or signs of infection. People with advanced cancer can still benefit, but the ASCO guideline notes some groups need to work with exercise professionals rather than exercising alone. Exercise should feel challenging but manageable; the talk test, being able to speak in short sentences, is a simple guide.

• 30 minutes, 3 times a weekModerate aerobic exercise
• 2 strength days2 sets of 8 to 15 reps
• 8 to 12 weeksMinimum for symptom benefits
• 150 to 300 minutesWeekly target for prevention
• Before lung surgeryPreoperative exercise may help
• Red flags mean stopChest pain, fever, new bone pain