Since exercise and health are passions of mine I am delighted to share this article:
"One of the most important benefits of exercise is in how it reduces our risk of developing a number of types of cancer — especially colorectal cancer, which according to some estimates is the malignancy most influenced by physical activity. But how workouts guard against colon cancer remains largely unknown. Physical activity speeds the movement of waste through the intestines, as anyone who has had to hunt for a bathroom during a workout knows. But this does not seem to fully account for the protective effects of exercise."
A small study that tested blood after exercise gives us some indications how how exercise might affect our health because of its affect on inflammation.
"They found a large increase in molecules involved in inflammation immediately after exercise. Inflammation can slow cell growth and reproduction." So the cancer cell growth might be slowed down because of the exercise.
Unfortunately, the benefit seems to b transitory so it looks like we need to keep exercising regularly to gain any benefits.