Regular physical activity reduces risk for invasive breast cancer, possibly by reducing levels of female hormones.
Researchers recently tracked breast cancer survival among more than 1,200 women diagnosed with breast cancer between 1990 and 1992.
The women were 20-54 years old at the time of their diagnosis (average age: 42). They recalled their physical activity level at age 13, 20, and the year before breast cancer diagnosis.
The association was particularly strong for women with a body mass index (BMI) of more than 25 -- the statistical threshold for overweight -- who also reported the highest levels of physical activity in the one year before their diagnosis. (For reference, a woman 5 feet 5 inches tall who weighs 150 pounds has a BMI of 25.)
Overall, women with rated in the highest 25 percent, in terms of their level of activity, were 21 percent more likely to survive than those rated in the bottom quarter. The benefits for women with BMI's above 25 who had high levels of activity rose; they were 30 percent less likely to die than those with BMI's above 25 who engaged in low levels of activity.
Most were diagnosed with breast cancer in the disease's early stage, when it hadn't spread beyond the breast or nearby area.
Most women were still alive eight to 10 years after diagnosis. But 290 died during that time.
Those who were overweight or obese at the time of breast cancer diagnosis -- and were also highly physically active in the year before -- had a survival rate 30% better than their inactive peers.
No such benefit was seen for women who weren't overweight or obese. But there was no downside to exercise for any of the women, in terms of breast cancer survival.
According to Page Abrahamson, PhD, was among the researchers who worked on the study, published in Cancer's Oct. 15 edition, "A beneficial effect was found on survival for exercise undertaken in the year before diagnosis, particularly among women who were overweight or obese near the time they were diagnosed with breast cancer." (Abrahamson worked on the study while at the University of North Carolina, Chapel Hill. She is now on staff at Seattle's Fred Hutchinson Cancer Research Centre.)
According to Page "While we were able to look for a more general association between exercise and survival, future studies may be able to assess more thoroughly the impact of specific types of fitness and exercise patterns. "
She further added, "Because few studies have investigated the impact of physical activity on breast cancer survival, more research in this area is warranted."
In particular, it is important to study the effects of exercise at different periods across the lifespan as well as the effect of specific types of activity. For breast cancer patients, this includes studying the effects of exercise undertaken following their diagnosis.
While physical activity is no substitute for medical treatment -- and often difficult for exhausted cancer patients -- the findings indicate breast cancer patients should try to exercise regularly after undergoing standard care to maximize their chances of surviving. If future research confirms that physical activity improves survival among women with breast cancer, programs and policies to promote such activity for this purpose may be adopted.