Doctors stunned to see strict exercise regimen is as good as medicine for colon cancer

Business Insider

14-06-2025

Scientists and doctors love to joke that exercise is a pretty great drug.
But can workouts really compete with chemotherapy to prevent a disease like recurrent colon cancer? That's been tough to prove — until now.
Results of the first randomized controlled trial of exercise as a treatment for recurrent high-risk cancer were presented at the American Society of Clinical Oncology's (ASCO) annual meeting in Chicago on June 1, and they stunned the crowd of doctors gathered there from around the world.
The 17-year trial included over 880 patients from around the globe, each recovering from high-risk stage 2 or stage 3 colon cancer after treatment. Half of the participants were given general advice about exercise and how it can improve cancer survival. The other half were given a structured, three-year exercise prescription to follow, with the goal of preventing recurrence or a new cancer diagnoses.
In the trial, exercise outperformed what adjuvant (or, secondary) chemotherapy can do to boost a patient's long-term survival, after surgery and primary treatment is over. Adjuvant cancer treatment is the kind designed to kill any extra cancer cells left behind, and prevent cancer from coming back.
"Exercise is no longer just an intervention that improves quality of life and fitness. It is a treatment," Chris Booth, the study's lead author and a medical oncologist at Queen's University in Ontario, told the crowd.
Brisk walking prevented recurrent colon cancer, plus new breast and prostate cases
In the study, patients who followed an exercise regimen reduced their risk of death by 37%, and reduced their risk of cancer recurrence and new cancer development by 28%.
The benefits of this three-year exercise prescription — which included advice and support from a trainer or physical therapist — were also long-lasting.
After eight years, 90% of patients in the exercise program were alive compared to 83% in the control group.
This 7% survival bump is comparable to (and in some cases exceeds) the survival benefits of standard drugs that doctors use in this same context. The common adjuvant chemotherapy drug oxaliplatin gives patients an overall survival boost of 5% after 10 years. Many other adjuvant cancer drugs deliver similar survival benefits, of around 5 to 10%.
The effect didn't seem to be due to other factors. Patients didn't lose weight or belly fat, and no meaningful difference was seen in fatal heart attacks. The exercisers also weren't turning into Olympic athletes; they were just doing the equivalent of about 1.5 to 2.25 extra hours of brisk walking each week.
In addition to reducing colon cancer diagnoses and deaths, the exercise also seemed to reduce the risk of other cancers. In the exercise group, there were two new cases of breast cancer diagnosed, compared to 12 cases among the controls.
Other cancer doctors at the conference were shocked at the magnitude of the effect even though they've always kind of known exercise is good for cancer. Exercise is generally recommended to patients in recovery to improve outcomes. But to beat standard chemotherapy drugs? That was impressive.
Dr. Paul Oberstein, a medical oncologist at NYU Langone who was not involved in the study, said he'd like to bring this treatment to his patients, maybe with some help from wearables like watches, and on-demand fitness classes people can access at home.
"If you could somehow package this and bill it as a drug, it would be very valuable because the benefit was really remarkable," he said.
Scientists are still figuring out why exercise is so great at preventing and treating cancer
Researchers are still studying the blood samples of patients who were in this study, drilling down into what might be driving the anti-cancer effects from exercise.
Oberstein suspects that exercise is probably doing something that's powerfully anti-inflammatory in the body, reducing tumor growth, and preventing cancer's spread. At least, that's what he observes when he studies mice on treadmills in his lab.
"Of course, mice on treadmills are not really people," he said, chuckling. "But what we see, and what we think might be applying, is that they have less inflammation."
Other researchers think that perhaps exercise is revving up the immune system, engaging in what's called "immune surveillance" against cancer.
"These are very hard things to measure over a long period of time," Oberstein said.
Booth, who's been an avid long-distance runner ever since he was a kid, said this treatment should now be offered to any recovering colon cancer patient who wants it.
"This intervention is empowering for patients, it is achievable for patients, and with a cost that is far lower than our standard," he said near the end of his talk.
Slowly, but surely, the whole crowd stood up and burst into a sustained and hearty standing ovation.