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1997/05/02 -As of this week, people who are waiting to begin an
exercise program until there is further evidence that exercise is
beneficial have fewer and fewer excuses. That's because two new scientific
studies show that exercise not only reduces the risk of breast cancer, but
that it can help people who have undergone chemotherapy reduce some
of its most debilitating side effects.
The concept that exercise can protect against cancer
is not new: research has previously shown the risk of cancer of the colon
and rectum, prostate, endometrium, breast and kidney are all
reduced in people who exercise. One of the new studies confirms the
protective effect on breast cancer. The other study shows that exercise
can help reduce the fatigue and loss of strength and endurance that
are common side effects of high dose chemotherapy.
In the first article, researchers at the University of Tromso,
Norway, found that physical activity during leisure time and
at work was associated with a reduced risk of breast cancer. This was a
retrospective study: the researchers studied the records of
25,624 pre- and postmenopausal women enrolled in health surveys during
certain years.
The researchers then identified 351 cases of invasive breast
cancer among the women being studied. They found that women who
exercised regularly during leisure time had a 37% lower risk of
developing breast cancer than did sedentary women. Women whose jobs involved
walking, lifting, or heavy manual labor also had reduced risks of
breast cancer as compared with sedentary women, with the greatest risk
reduction among women with the most strenuous work. The effect was greater in
premenopausal women than in postmenopausal women. Researchers
speculate that exercise exerts its protective effect on breast tissue
by altering levels of natural hormones. This study was published in the
May 1, 1997 issue of the New England Journal of Medicine and confirms
several earlier epidemiologic studies on the benefits of moderate
exercise in preventing breast cancer.
The finding that exercise can reduce side effects from high dose chemotherapy was reported in the second study. This result is
especially intriguing because cancer patients recovering from this
regimen are often advised to rest and limit their daily activities.
According to the new study, that well-meaning recommendation
may inadvertently create a long-lasting spiral effect: diminished
activity leading to easy fatigability which causes further diminished
activity, and so on. This study compared 16 patients in a control (no
exercise) group with 16 patients who participated in a medically
supervised program of gradually increasing aerobic exercise over a
period of six weeks. By exercising to keep their muscles in shape,
patients regained their strength and energy levels better, which, in turn, made
everyday tasks, from climbing stairs to grocery shopping, easier.
Since the study was small, the authors recommend a larger randomized study to
further evaluate the effects exercise on the quality of life of
cancer patients after high dose chemotherapy. This study took place at
Freiburg University Medical Center in Freiburg, Germany and was
published in the May 1, 1997 issue of the journal CANCER.
Taken together, these studies add to the substantial
evidence on the benefits of exercise. The American Cancer Society recognizes the
importance of exercise to overall good health and recommends that
healthy individuals be at least moderately active for 30
minutes or more on most days of the week and stay within a healthy weight
range. Patients should ask their physicians about an exercise program
appropriate to their individual medical condition.
"Medical scientists are learning much more about the
value of exercise and the maintenance of health in prevention as well
as treatment," says Harmon Eyre, MD, Executive Vice President of
Research and Cancer Control for the American Cancer Society. "We
anticipate that more studies along this line will be done with positive outcomes."
References:
- Demeo FC, Tilmann MHM, Bertz H, et al. Aerobic exercise in
the rehabilitation of cancer patients after high dose chemotherapy and
autologous peripheral stem cell transplantation. CANCER, 1997;
79(9):1717-1722
- Thune I, Brenn T, Lund E, Gaard M. Physical activity and
the risk of breast cancer. New England Journal of Medicine, 1997; 336
(18):1269-1275
- American Cancer Society 1996 Advisory Committee on Diet,
Nutrition, and Cancer Prevention. Guidelines on Diet, Nutrition, and
Cancer Prevention. Guidelines on Diet, Nutrition, and Cancer
Prevention: Reducing the Risk of Cancer with Healthy Food Choices and
Physical Activity. CA Cancer J Clin, 1996; 46 (6): 325-341.
Joann Schellenbach
National Director Media Relations
American Cancer Society
212-382-2169
jschelle@cancer.org
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