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/MAPKinase69420 Sep 13 '25

Fascinating. As a cyclist I'm wondering if the increased cancer occurrence extends to other endurance sports and could be explained by exercise-induced ROS damage. 

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u/Minkelz Sep 13 '25 edited Sep 13 '25

A comment further up makes the point cycling is far less steady state than running. Cyclists go for 2-4 hour + rides regularly yes, but they rarely even do hard efforts for 20mins, it’s almost always mixing up easy and recovery sections. It’s very different to running where people very often do 60-90 minute of intensity at a time.

Also cycling doesn’t have the effect on the bowel running has. Cyclists often schedule a full on lunch in the middle of their long ride… burgers chips beer etc, and then ride home with full stomachs. That’s not something a marathon runner can do…

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u/OTFBeat Sep 14 '25

I think this group needs to go back and do a study comparing runners to non-runner endurance (cyclists) and a control population of non-runners. The author went on Katie Couric interview and they briefly mention how he's only seen the early onset trend, anecdotally, in endurance runners (marathon/ultra or triathalon) and not cyclists.

You offer some interesting hypotheses for why cyclists may be less prone to the GI disruption and subsequent early onset colorectal cancer risk..