Researchers from Brigham and Women's Hospital and Harvard University tested the hypothesis that physical activity increases survival rates among women with breast cancer. They reported their findings at the 95th Annual Meeting of the American Association for Cancer Research.
"We already knew that exercise improves the quality of life after a breast cancer diagnosis," said lead investigator Michelle D. Holmes, M.D., Dr.P.H., "but little is known about how physical activity affects survival."
Holmes and her team drew on participants in the Nurses' Health Study, reviewing data on women with stages I, II, and III breast cancer, diagnosed between 1984 and 1996. In that study, leisure-time physical activity is measured in metabolic equivalent task hours per week (met-hours/week - one met is the energy expenditure and caloric requirement at rest. One hour of walking represents three met-hours of physical activity.) The researchers looked specifically at exercise beginning two years after diagnosis, in order to avoid inclusion of women undergoing treatment. The cohort of 2,296 women were followed from 1986 until either their death from breast cancer or June 2002, whichever came first.
Taking into account the stage of disease, obesity and other factors, the relative risk of death from breast cancer was decreased with every level of physical activity compared with being sedentary. The risk of death from breast cancer was 19 percent less among women who undertook 3-8.9 met-hours/week of exercise; 54 percent less for 9-14.9 met-hours/week; 42 percent less for 15-23.9 met-hours/week; and 29 percent less for 24 or more met-hours/week of recreational exercise.
"We were able to show that even a moderate amount of physical activity improved the odds of surviving breast cancer," Holmes said. "It is especially heartening for women recovering from breast cancer to know that the benefit is as readily accessible as walking for 30 minutes on most days of the week."
SOURCE:
95th Annual Meeting of the American Association for Cancer Research, March 29, 2004, Orlando, Florida
