Endurance Sports and Colorectal Cancer: Is There a Connection?

Timothy L. Cannon, MD, is board certified in medical oncology, hematology and internal medicine. He serves as the Sheridan Director, Molecular Tumor Board and Co-Director of the Gastrointestinal Cancer Program.

After treating three ultramarathoners who had developed colorectal cancer in recent years, I had a suspicion: This could be more than a coincidence.

I found additional reason to believe that there could be a connection between endurance sports and increased risk for colorectal cancer when I read research on the reduction of blood flow to the stomach, intestines and nearby organs that often occurs during strenuous exercise. More research seemed to be in order.

One of the great things about working with the Inova Saville Cancer Screening and Prevention Center is that we are able to act on these ideas. So, as of Sept. 16, the Saville Center is running a study of 100 endurance athletes to see what we can learn.

It’s important to note that we are examining a small aspect of a much bigger problem. Colorectal cancer is expected to cause more than 50,000 deaths in the United States in 2022.

And while overall rates have declined, we have seen a rise in colorectal cancer rates for American adults under the age of 50. According to the American Cancer Society, colorectal cancer rates have been increasing since the mid-1980s in adults ages 20 to 39, and since the mid-1990s in adults ages 40 to 54. Those in the younger age groups have seen the steepest increase.

While focusing on a small subset of young adults, the Saville Center study has the potential to be quite meaningful. It could provide clues about at least one way that people develop colorectal cancer at a relatively young age.

A Study Focused on Extreme Endurance Athletes

We know that the body behaves differently during and after an endurance event like an ultramarathon.

Over the course of a 50-mile race — six or seven hours for an elite athlete — the body re-routes a significant amount of blood flow from the gut to the active muscles in legs. The loss of blood flow to the gut during this intensive exercise can cause ischemia, resulting in cellular damage, and a more disorderly and rapid process of cell turnover.

I had not seen research that takes the logical step of associating ischemia with cancer, but I became interested in the possibility that they are tied together. Along with Stephanie Van Bebber, the senior director of Inova’s Clinical Trials Office, we created a plan for the study.

The study is currently recruiting 100 athletes ages 35 to 50. We are focusing on athletes at an extreme — they need to have run two or more ultramarathons (50 miles or longer).

The athletes will be screened for colorectal cancer, and the results will be compared to the historical averages. As a reference point, for adults ages 45 to 50, the rate of finding precancerous polyps is about 3%.

And if we discover cancer, of course we will offer treatment.

What We Can Learn From the Study

We believe this study will be the first of its kind. And while I am inclined to believe that there’s an association between extreme endurance sports and increased cancer risk, this study — with just 100 subjects — may not deliver definitive proof.

Even without such proof, the study could save the lives of endurance runners. And as someone who enjoys long distance running themselves, this even feels personal. It could elucidate a principle behind the development of cancer that was previously unknown, leading to additional discoveries and cancer prevention.

That’s important. And since I have treated endurance athletes who developed this cancer, two of whom died from the disease, it’s personal for me, as well. I’m grateful that the Saville Center makes a study like this possible.

Understanding the larger issue — what is causing the increased incidence of colorectal cancer in young adults — will take much more study. And at Saville Center, we plan on contributing to that body of knowledge, as well.

Learn more about the Inova Saville Cancer Screening and Prevention Center or schedule a consultation.