Cancer
Moderate exercise betters odds of beating breast cancer
By David Liu Ph.D.
May 25, 2005 - 10:22:00 PM

Women with breast cancer can drastically increase their odds of beating the disease if they do moderate physical exercise after diagnosis, which is equivalent to waking one more hour per week, according to a study published in the May 25 issue of JAMA.

Researchers explained that the reason physical exercise improves the odds of breast cancer survival rate is because physical exercise can reduce the female hormone (estrogen) levels.

Lower levels of ovarian hormones caused by physical exercise in the breast cancer patients could potentially improve the breast cancer survival rate.

The study, conducted by Dr. Michelle D. Holmes and colleagues at Brigham and Women’s Hospital and Harvard Medical School and colleagues, was to examine whether higher levels of physical activity after a breast cancer diagnosis would benefit breast cancer survival.

The study involved 2,987 female nurses with breast cancer at different stages diagnosed between 1984 and 1998. The breast cancer patients were participating in the Nurses’ Health Study. They were continually checked until their death or June 2002.

Physical activity was measured in metabolic equivalent task (MET) hours. Three MET-hours is equivalent to walking at an average pace of 2-2.9 mph for one hour, according to the study.

It was found that compared with women who engaged in less than 3 MET-hours per week of physical activity, those who did 3-8.9 MET-hours per week lowered their risk of death from breast cancer by 20 percent; those who did 9-14.9 MET-hours per week by 50 percent; those who did 15-23.9 MET-hours per week by 44 percent; and those who did 24 or more MET-hours per week by 40 percent.

Physical exercise is particularly beneficial to those with hormone-responsive breast cancer. Nine or more MET-hours per week of physical activity can lower the risk of breast cancer death by 50 percent in women with hormone-responsive breast cancer, compared with those who did 9 MET-hours per week of physical exercise.

The absolute unadjusted risk of breast cancer death at 10 years was lowered by 6 percent in women who engaged in 9 or more MET-hours per week of physical exercise.

According to the authors, women with breast cancer who follow the recommendations of the Centers for Disease Control and Prevention to exercise at moderate intensity for 30 or more minutes per day for five or more days per week may survive longer. However, only one-third of breast cancer survivors participate in levels of physical activity recommended by government agencies.

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