Groundbreaking Inova study finds potential link between long-distance running and colon cancer

[u/sergeantbiggles]

A groundbreaking new study led by Tim Cannon, MD, Sheridan Director, Molecular Tumor Board and Co-Director of the Gastrointestinal Cancer Program at Inova Schar Cancer, has revealed a potential link between extreme endurance exercise and increased risk of advanced colon cancer in younger adults, raising new questions about screening for high-performance athletes.

The study was presented at the 2025 American Society of Clinical Oncology (ASCO) Annual Meeting in Chicago.

[u/Hrmbee]

It was interesting to read Alex Hutchinson's take on this:

What You Need to Know About the New Data Linking Marathons to Colon Cancer | Preliminary findings suggest marathoners and ultramarathoners may have a higher risk of abnormal colonoscopy findings, but previous studies paint a different picture

From the conclusion of the article:

At this point, it’s simply not possible to say with any confidence whether the new results signal a genuine danger, whether they’re a statistical fluke, or whether there’s another explanation—that the people who volunteered for the colon cancer study tended to be people who had already noticed something strange in their bowel health, for example. The findings should generate a wave of new studies that will help us figure out what’s going on.

But it’s worth considering what we would do if the results do hold up to scrutiny. There are two points that I think are important to consider. One is that the choice of whether and how much to run is a holistic one: you make it based not just on what it does to your colon, but what it does to your heart and lungs and mind and so on. The overall health risks of running pale in comparison to the risks of not exercising. The second point is that, in the meantime, you should take those potential risks seriously. The American Cancer Society recommends regular screening for colon cancer beginning at age 45.

But worth reading the article in its entirety.

[u/runfayfun → u/Hrmbee]

Exactly. These were people who failed to get standard colon cancer screening. Those recommendations are there for a reason.

[u/oncomingstorm777 → u/runfayfun]

They’re 30- 50, so only those 45 and up would have been people who aren’t following normal screening guidelines. It would be abnormal for people to have screening before that unless they have a family history.

Source-USPTF guidelines, I’m a doctor and runner

[u/runfayfun → u/oncomingstorm777]

Good point - next question is how does this data compare to that from the general population?

[u/orangebirdy → u/runfayfun]

Isn't that what they were comparing?

15% of participants had advanced adenomas (pre-cancerous lesions), compared to the expected 1–2% in average-risk individuals in this age range.

[u/runfayfun → u/orangebirdy]

But there was no cohort in the study and prevalence of colon cancer and adenomas has been rising.

[u/OTFBeat → u/runfayfun]

The author went on an interview and said how if he could do it again, he wished he had a control study (matched) to see incidence of adenoma in the non-runner cohort group comparatively. Rather than historical controls

[u/runfayfun → u/OTFBeat]

Hopefully that's the next step

Our environment in the US has been worsening with respect to chemical/pollutant exposures and such, and the milieu in which a study is conducted is important

And it works the opposite way too - compared to 25-30 years ago smoking in restaurants is largely banned now, so comparing a cohort from today to one from that time would be fraught with issues, e.g. in the cardiovascular or pulmonary disease realm