New research shows that exercise may help women's immune systems recover after chemotherapy for breast cancer.

The finding comes from a study of 49 women with breast cancer, 28 of whom were assigned to a six-month exercise program. Blood tests showed better immune response and less inflammation in the exercise group.

"We're pleased to find evidence that appropriate exercise can help a breast cancer survivor's immune system bounce back after therapy," says Andrea Mastro, PhD, in a news release. She is a Pennsylvania State University professor of microbiology and cell biology.

The results were reported in Philadelphia at the Era of Hope meeting of the U.S. Department of Defense's Breast Cancer Research Program.

In May, a much larger study of 3,000 women showed that getting just a little exercise can improve a woman's chances of surviving breast cancer. That report appeared in The Journal of the American Medical Association's May 25 issue.

Read Web MD's "Some Breast Cancers May Not Need Chemo."

Chemo's Immune System Effects

Chemotherapy is widely used in breast cancer treatment. It's highly effective, but it affects healthy cells as well as cancerous ones. For instance, levels of infection-fighting "T cells" often fall as a result of chemotherapy.

"We know that chemotherapy-induced decreases in T cells can persist for many years, and data from the literature suggest that, in the period immediately following chemotherapy, the surviving T cells may be weakened as well," says Mastro.

Mastro and colleagues say they had learned of another study in which AIDS patients on a six-month mixed-exercise program had an increase in T cells. With that in mind, they hypothesized that breast cancer patients might also get an increase in lymphocytes, which include T cells.

Read Web MD's "New Breast Cancer Chemo Drug May Aid Survival."

Exercise Test

The two groups of women in Mastro's study were similar in age, education, cancer treatment, cancer stage, overall health, body mass index (BMI), and diet, says the news release.

Women in the exercise group usually started working out within a month after completing chemotherapy. They all followed a similar plan: stretching to warm up, use of flex bands for resistance training, and an aerobic activity of their choice (treadmill, stationary bike, or walking). They also got personal training from a kinesiology intern.

The workouts were designed to allow the women to work out at the research center or at home during the second half of the study, says Mastro. Most women stuck with their trainers at the center; the rest kept exercise diaries and checked in with their trainer by phone or in weekly visits to the center.

Many women said they had rarely if ever exercised before their breast cancer diagnosis. Those who said they had previously exercised favored walking. More than three quarters of the exercise group finished the program, says the news release.

Read Web MD's "The Latest Treatments for Breast Cancer."

Better Immune Results Seen

The exercise group reaped aerobic and muscular benefits, as you might expect. But those weren't the only benefits.

Compared with the other women in the study, the women in the exercise group also boosted their number of activated T cells, made more lymphocytes, and lowered their levels of an inflammatory marker. That data came from blood tests done after chemotherapy and at the study's midpoint and end.

It's always a good idea to check in with your doctor before starting a new exercise program, even if your body hasn't been through anything as grueling as chemo. However, Mastro says that when she and her colleagues were recruiting women for the study, some said their doctors had told them not to exercise after therapy.

Read Web MD's "You Survived Breast Cancer: Now What?"

Similar Findings

Improvements in T cells with post-chemo exercise were also recently reported by Canadian researchers. They say they saw the benefit in a small group of postmenopausal breast cancer survivors who worked out on stationary bikes three times per week for 15 weeks.

Those findings were reported in April's Journal of Applied Physiology. The same experiment was also the basis for a report in May's Journal of Clinical Oncology. In that paper, the researchers highlighted better quality of life and cardiopulmonary function for the breast cancer survivors who exercised.

Mastro says that although her study's program included resistance training, she considers the two studies to be complementary.

Visit WebMD's Breast Cancer Health Center

By Miranda Hitti, reviewed by Charlotte E. Grayson, MD

SOURCES: "Era of Hope" Department of Defense Breast Cancer Research Program Meeting, Philadelphia, June 8-11, 2005. News release, Department of Defense. WebMD Medical News: "Exercise Raises Odds of Beating Breast Cancer." Fairey, A. Journal of Applied Physiology, April 2005; vol 98: pp 1534-1540. WebMD Medical News: "Breast Cancer Survivors: Get Moving."