Exercise Beneficial In Breast Cancer Radiation Therapy

FLINT, Mich., Oct. 9 -- Moderate aerobic exercise may make adjuvant radiation for breast cancer more tolerable, found researchers here.

Twenty to 45 minutes of aerobic exercise three to five times a week maintains red blood cell levels and reduces fatigue, anemia, and depression, reported Jacqueline Drouin, Ph.D., of the University of Michigan at Flint, and colleagues, online in Cancer in advance of the Nov. 15 issue.

A small randomized controlled trial showed that aerobic exercise may be a "safe, effective, and economical method for improving physical fitness and maintaining erythrocyte levels in females undergoing radiation treatment," the authors wrote.

The researchers enrolled 20 sedentary women with breast cancer and randomized them to either an individualized aerobic walking program or to a stretching program, which served as the placebo control.

Measurements of peak aerobic capacity and serum blood were taken a week before radiation treatment was to begin and again a week after it ended, Dr. Drouin and colleagues said.

The average training duration was between eight and nine weeks, the researchers said.

The study found:

• Average peak aerobic capacity in the exercise group increased by 6.3%, which was significant at P=0.001. In the placebo group, capacity fell 4.6% (not statistically significant).
• Red blood cell counts increased 2.68% (NS) in the exercise group but declined significantly (by 2.55%) in the placebo group. Both the placebo group change and the between-group differences were significant at P=0.014.
• Hemoglobin rose 0.81% (NS) in the exercise group but fell significantly (by 3.91%) in the placebo group, at P=0.009. The between-group difference also was significant at P=0.009.
• The same pattern was seen for hematocrit, which increased 2.10% (NS) in the exercise group and fell significantly (by 2.46%) in the placebo group. The placebo group change and the between-group change were significant at P=0.045 and P=0.046, respectively.

The implication, Dr. Drouin and colleagues said, is that moderate aerobic exercise can forestall the decline in red blood cells associated with radiation therapy for breast cancer.

The main limitation of the study is the small sample size, the researchers noted, which meant it did not have enough statistical power to determine whether the changes seen in the training group were significant.

Also, although the aerobic exercise was monitored, there was no control of what the patients ate, which might also have had an effect on red blood cells, they said.

Earlier studies of the effect of exercise on red blood cells measures in people with cancer had mixed results, the researchers said. One, involving six weeks of treadmill walking after high-dose chemotherapy and autologous stem cell transplantation, showed a clear benefit. Two others, however, found no benefit, possibly because training was not intense enough, the researchers said.