Dana Farber Cancer Institute put together this fact sheet indicating that exercise can lower the risk of recurrence of different cancers. Most of the studies have been done on breast cancer and colon cancer.

Concerning breast cancer: “A review of the effect of lifestyle factors on breast cancer mortality found that physical activity is consistently linked to a lower risk of breast cancer recurrence. A large study showed that women who exercised moderately (the equivalent of walking three to five hours a week at an average pace) following a breast cancer diagnosis had 40 to 50 percent lower risks of breast cancer recurrence and death from breast cancer or any cause, compared with women who exercised less. The benefit of exercise was particularly apparent in women with hormone-responsive breast tumors.

“Another study found that women with breast cancer who exercised for the equivalent of walking at an average pace of 2 to 2.9 miles per hour for one hour per week had a 35 to 49 percent lower risk of death from breast cancer, compared with women who were less active.”

Another study, by Holmes et al, published in JAMA, the Journal of the American Medical Association, likewise indicated that physical activity after a breast cancer diagnosis may reduce the risk of death from this disease.