A landmark phase III trial found that patients who followed a supervised exercise program after completing chemotherapy for colon cancer had a 28% lower risk of their cancer coming back — and a 37% lower risk of dying.
This trial asked whether structured, supervised exercise — not just general advice to "stay active" — could reduce the chance of colon cancer coming back after standard treatment, and whether it helped patients live longer.
For years, observational data suggested that people who were more physically active after a colon cancer diagnosis tended to do better — fewer recurrences and longer survival. But that kind of data has a catch: healthier patients may simply be more able to exercise in the first place. Only a randomized trial — where patients are assigned to exercise or not — can show whether exercise itself is responsible.
The CHALLENGE trial set out to do exactly that, enrolling 889 patients across 55 centers in six countries. Its main measure was disease-free survival — the time from the end of treatment until the cancer returns, a new cancer develops, or death.
Between 2009 and 2024, 889 patients who had completed surgery and adjuvant chemotherapy for stage III or high-risk stage II colon cancer were randomly assigned to one of two groups, 2 to 6 months after finishing chemotherapy. Ninety percent had stage III disease, and patients were followed for a median of 7.9 years.
The exercise group (445 patients) worked with a certified physical activity consultant for three years — frequent support at first, tapering to monthly check-ins. The goal was to add at least 10 MET-hours of aerobic exercise per week — roughly 45–60 minutes of brisk walking three or four times a week. Patients chose their own activity.
The comparison group (444 patients) received health-education materials and standard surveillance. This group also grew somewhat more active over time — which means the true benefit of the structured program may be even larger than the results suggest.
One of the most common conversations I have had over the years goes something like this. A patient — let's call him Robert — comes to see me three months after finishing chemotherapy for stage III colon cancer. It was tough, he had an allergic reaction to one of the drugs, and then battled loose stools in the last couple of cycles. He needed a special kind of intravenous line (called a PICC line), and was no doubt a very happy camper when he rang the gong at the end of all of it. Now, three months later, he feels pretty much back to his normal self, except when he walks on a cold floor and feels the tingling in his toes. Now that he has finished all the chemotherapy we prescribed, he has a question he's been turning over for weeks.
"Is there anything more I can do?" he asks. "To help stop it coming back?"
For most of my career, my honest answer was incomplete. I could tell him that a healthy lifestyle, which included exercise, was probably helpful, but I couldn't be more concrete than that. The CHALLENGE trial has changed that answer.
The results were striking — and clinically meaningful. Patients in the structured exercise group were significantly less likely to have their cancer return or to die during the follow-up period.
One striking detail: the benefit wasn't only fewer colon cancer recurrences. The exercise group also had fewer new primary cancers — particularly breast (0.4% vs 2.7%) and prostate (1.1% vs 2.0%) — hinting that exercise may act more broadly, perhaps through immune surveillance, reduced inflammation, or metabolic changes, rather than simply clearing residual colon cancer cells.
Notably, exercise did not reduce body weight or waist size, so weight loss does not appear to explain the benefit. The trial authors pointed out that the magnitude of the survival benefit rivaled that of many approved colon cancer drugs — remarkable for something far cheaper, with broad health benefits beyond cancer.
View the full trial record on ClinicalTrials.gov The Results tab includes links to associated publications — the NEJM paper may be accessible via your library or institution
NCT00819208 ↗This is the first randomized controlled trial to show that structured exercise — not just general advice to stay active, but a supported, personalized program — reduces the risk of colon cancer returning and helps patients live longer. The trial authors concluded it should be incorporated into standard care.
If you have completed treatment for stage III or high-risk stage II colon cancer, asking your oncologist about a structured exercise program is now an evidence-backed conversation. The target is not an athlete's regime — it is roughly 45–60 minutes of brisk walking three or four times a week, with professional support to build up and sustain it. Whether the same holds for other cancers is not yet known, though the lower breast and prostate cancer rates are intriguing and are being studied.
I love to talk about the CHALLENGE trial when patients come to see me a few months after chemotherapy. Patients like Robert, who are motivated and healthy, take the advice in stride, and start counting daily steps almost immediately. The beauty of the trial was that it did not involve complicated weight lifting or fancy machines — just a couple more hours of walking per week. Now that's a prescription I'll always be eager to write.
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