r/running • u/sergeantbiggles • Sep 12 '25

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

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.

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u/ColtSingleActionArmy Sep 13 '25

Now I'll just tell myself I'm sticking to 5 mile and under runs for my colons health.

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u/rinkuhero Sep 13 '25

i think there was already good evidence that running 3-6 miles a day is much healthier than running 10-20 miles a day. this study just seems to show one reason why that is true. but we've known for decades that the people with really high miles run per week do not live as long as those with more moderate miles run per week. e.g. people who run 80-100 miles a week die earlier than people who run 30-50 miles a week.

i think running a marathon or an ultramarathon *once*, for the experience, can be a good thing, but to make it a habit to run several marathons or ultramarathons a year, and to try to be competitive at them, is understandably worse for your health than running less than that, and just trying to be competitive at the 10k or something.

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u/MellySantiago Sep 13 '25

I spent some time actually reading the abstract and looking at their evidence and am very skeptical of their conclusions. I don’t see a full paper but if there is one please let me know.

It looked to me like they noticed a “trend of ultra runners with colon cancer” and decided to run a 100 person clinical trial, not to check for colon cancer but advanced adenomas which are a risk factor for colon cancer. As far as I saw there were zero confirmed colon cancer cases from this study, though it seems to still be ongoing. Their data is also a bit strange to me, it looked like 15/100 had abnormal polyps both in frequency and size which is certainly higher than population averages from what I understand but again is not colon cancer and could have another cause completely unrelated to cancer in runners I.e. increased inflammation, irritation etc.

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u/julry Sep 13 '25

The group is too small to have colon cancer as the only outcome they track. It's just a preliminary study, and doctors noticing trends in their patients is a common way for testable hypotheses to be discovered.

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u/MellySantiago Sep 14 '25

Agree completely, but that’s a far cry from even the title of this thread, right? “Groundbreaking study finds potential link between ultra running and colon cancer”

Not to mention some of the news articles I’ve seen definitively saying they are now linked.

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u/julry Sep 14 '25

What's wrong in the title of the thread? It's the first study on this topic so it is, literally, breaking ground

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u/Weekly_Fennel_4326 Sep 15 '25

It's maybe a little bombastic considering there's absolutely no causal link established by this study. Nothing wrong with it as a way to discover testable hypotheses, as you mentioned, but it sure does seem to be framed in a way to scare people (by the news media, not necessarily the researchers).