Exercise after chemotherapy for breast cancer boosted the activity of infection-fighting T cells in women who worked out regularly, according to data from a study conducted at Penn State University under the direction of Andrea Mastro, professor of microbiology and cell biology. Mastro's findings indicate that exercise can help restore immune systems damaged by anti-cancer drugs, which destroy healthy as well as malignant cells.
Mastro will present the research at the "Era of Hope" meeting of the Department of Defense Breast Cancer Research Program in Philadelphia, Pennsylvania, on 10 June 2005. The meeting will include presentations by Mastro and other scientists who are developing a better understanding of the role of everyday choices people make about activities such as eating and fitness regimens in causing or preventing disease.
In Mastro's study, women between the ages of 29 and 71 were assigned to an exercise group of 28 women or a non-exercise group of 21 women. Women in the exercise group began the exercise routine within a month of completing post-surgical therapy. All exercisers followed a similar regimen--stretching to warm up, use of flex-bands for resistance training, and an aerobic activity of their choice: treadmill, exercise bike, or walking. In the exercise group, each woman was paired with a kinesiology intern who served as a personal trainer.
"For the first three months, the women worked out with the trainers at our clinical research center three times a week for about 60 to 90 minutes, at a level the trainers determined was appropriate," Mastro explains. "We designed an exercise program that could be done without a gym, and for the second three months, participants had the option of working out at home."
Most of the exercisers preferred to continue with the personal trainers at the research center. Women who chose to work out at home kept an exercise log, which they discussed with the trainer during telephone interviews or weekly visits to the Penn State University Park campus. During the first three months, compliance with the exercise regimen was about 82 percent, dropping to 76 percent during the second three-month period. According to feedback, distance from the campus was a factor in the dropout rate.
Testing was conducted before the intervention, at three months, and at six months. Measurements for some immune functions improved, with exercisers showing more activated lymphocytes than non-exercisers. Additionally, concentrations of an inflammatory substance (IFN-_) that indicates trauma such as that caused by cancer treatment decreased in the exercisers but increased in the non-exercisers during the first three months. Another assay suggested that lymphocytes damaged or killed by cancer therapy were replaced more quickly in the exercise group with new and responsive lymphocytes--those that can respond to foreign substances by dividing to create more invader-fighting cells.
"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," Mastro said. "That's why we're pleased to find evidence that appropriate exercise can help a breast-cancer survivor's immune system bounce back after therapy." She noted that, during the recruitment phase, some women said that their doctors had counseled them not to exercise after therapy.
Additional test results showed improvements in various physical functions, such as endurance, upper-body strength (grip strength, biceps, triceps), and volume of oxygen intake (VO2max). For women who exercised throughout the program, these measures of physical function were better at six months than at three months. On a standard questionnaire, exercisers also scored higher on overall quality of life, social well-being, and fatigue levels than the non-exercisers. There were no differences in results between women who exercised at home or at the research center.
There were no significant differences between the two groups in education, cancer treatment, or stage, age, overall health, body mass index, or diet. In both groups, equal numbers of women had lumpectomy or mastectomy, most of the women had the same chemotherapy followed by radiation therapy, and most reported doing little if any regular exercise before diagnosis. Among those who had exercised before their diagnosis, walking was generally the activity of choice. The study excluded women who had other serious health conditions or took drugs that could affect the immune system.
Another study, conducted in a similar population by Canadian researchers and published in the April issue of the Journal of Applied Physiology, also found that exercisers had a greater percentage of activated T cells. Although that research was conducted for three months rather than six and examined aerobic conditioning rather than resistance training, Mastro considers the two studies to be complementary.
As a follow up, Mastro hopes to conduct a retrospective study of breast-cancer survivors to determine whether their immune systems are still depressed five years after treatment.
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