Natural Cancer Treatment - Can Exercise Really Prevent Cancer From Spreading?

Exercise is well recognized as being a factor which can reduce the risk of cancer by an average of about 30-40%, with some cancers being reduced by up to 70% in some studies. But what is the situation with people who already have cancer? Can exercise help to reduce the risk of recurrence or even death? There are studies which indicate this is the case in breast and colon cancers and possibly others as well.