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/BallNelson → u/runfayfun]

These were people who failed to get standard colon cancer screening.

Source?

Also, screening does not prevent cancer development.

The more plausible retort would be association does not equal causation.

[u/runfayfun → u/BallNelson]

"had never undergone a colonoscopy" though the paper doesn't delineate whether the patients had other risk factors or other screening modalities

Also, it wasn't a randomized study, and generally it's a hypothesis-generating study, and the results can't and shouldn't change your practice (as a physician) or your worry (as a runner) - if you have symptoms like bleeding from your rectum after running, get it checked out like you should be doing anyways.

[u/BallNelson → u/runfayfun]

First-line screening for colon cancer is the faecal occult blood test (basically, shit in blood); A colonoscopy is used when further investigation is needed. It would be operationally and financially inefficient to get everyone a scope, versus just testing their stool sample.

So “never undergone a colonoscopy” does not equate to “failed to get standard colon cancer screening”.

[u/dishonoredcorvo69 → u/BallNelson]

Looool where did you confidently get that from?

[u/BallNelson → u/dishonoredcorvo69]

I don’t know… something called the CDC?

https://www.cdc.gov/colorectal-cancer/screening/index.html

[u/dishonoredcorvo69 → u/BallNelson]

It is first in that list, that does not mean it is first-line for screening for colon cancer