Breast Cancer and Exercise

According to the American Cancer Society, one woman in seven gets breast cancer during her lifetime. Fortunately, earlier detection and improved treatment are improving the survival odds. Current treatment involves a variety of harsh remedies that often include lumpectomy or mastectomy, radiation treatment and chemotherapy. A new study, published in the Journal of the American Medical Association (v 293, p 2479, 2005), provides results from a study that could provide women with an additional weapon in their arsenal in surviving breast cancer - exercise!

The report summarizes a observational study involving almost 3000 female registered nurses who were diagnosed with stage I, II or III breast cancer between 1984 and 1998. Followup continued till June 2002, (or death, if that occured earlier). The study divided the patients into goups, based on their energy expenditure in exercise. The bottom line is that exercise decreases the risk of death by a Risk Ratio of 0.6 (40% reduction in mortality). The Margin of Error is approximately 0.5 to 0.7. The required amount of exercise is equivalent to taking a walk ( at 3 miles per hour) for one hour, three times a week. Additional exercise did not seem to improve the survival odds.

We note that observational studies can contain inherent biases - it was this general type of study that initially led to the erroneous conclusion that hormone replacement therapy was beneficial to menopausal women. However, given the relatively large reduction in mortality, its statistical significance, and the experience gained in such studies since the initial hormone studies, make it worth while to try exercising. Each increment in survivability contibutes to the ability of women to overcome this devastating disease.

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