The benefits of exercise for cancer patients are well known: in both younger and older patients, physical activity has been shown to improve quality of life, reduce symptoms such as fatigue and shortness of breath, and speed recovery after surgery. That comes as no surprise—increasing physical fitness makes almost everyone feel better, whether they have cancer or not.

But exercise is more than just a feel-good remedy: observational studies have demonstrated that moderate physical activity, such as walking 3 to 5 hours per week, reduces the risk of cancer recurrence and significantly improves survival after cancer treatment. How exercise might help prevent cancer recurrence is poorly understood, but a preliminary study presented at the American Physiological Society’s Integrative Biology of Exercise VI meeting earlier this month suggests that its immune system effects may be key.

In the study, lead investigator Laura Bilek, PhD, and colleagues investigated the effects of exercise on T cells, a majority of which become senescent after chemotherapy and therefore less able to attack cancer cells. The researchers recruited 16 cancer survivors, all but one of whom had completed treatment, and supervised them in a 12-week whole-body exercise training program. “The subjects performed aerobic exercise and resistance exercise at moderate intensity relative to that individual at his or her stage of recovery,” Dr. Bilek said. Blood samples were drawn before and after the training program and the proportions of senescent and naïve T cells were determined. In a majority of subjects, the ratio of senescent to naïve T cells changed favorably due to an increase in naïve T cells.

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“What we’re suggesting is that with exercise, you might be getting rid of T cells that aren’t helpful and making room for T cells that might be helpful,” Dr. Bilek said. She proposed that both individuals with cancer and cancer survivors would benefit from the heightened “cancer surveillance”—the ability of the immune system to recognize cancer cells—that exercise may bring. “This is a preliminary study to guide the design of a larger clinical trial to more definitively answer questions about how exercise may positively impact the immune system in cancer patients,” Dr. Bilek added.

Other recent research has pointed to additional avenues by which exercise may reduce cancer occurrence or recurrence. Tai chi may have beneficial effects on the immune system, according to a study conducted in China that recruited 32 subjects with non-small cell lung cancer. In control subjects, T1/T2 and Tc1/Tc2 ratios declined after surgery, indicating a reduction in immune system function, whereas no such decline occurred in subjects who participated in a 16-week tai chi program.

A preliminary study conducted at the University of Colorado among 64 healthy adults found that increasing physical activity over a 12-month period was associated with a reduction in DNA methylation of breast cancer genes, a process key to the development of malignancy.

Unfortunately, many cancer patients reduce their physical activity level just when they need exercise the most, as shown in a German study of breast cancer patients, whose median activity level declined significantly during and 1 year after treatment. One key reason that cancer patients don’t exercise: no one recommends it to them. None of 20 patients with non-small cell lung cancer who were interviewed by researchers reported that their oncologist discussed exercise with them or said more than that they should “stay active.”

Readers, we want to hear from you: Are your cancer patients aware of the benefits of exercise? Do you recommend exercise for your patients with cancer? Tell us in the comments section below.