Exercise and Breast Cancer Risk

Two studies came out this month about strenuous exercise lowering breast cancer risk for reoccurrance. Both studies hypothesized that reduction in weight gain, increased immune activity and/or changes in metabolism could be a contributing factor. With studies like these, there is very little risk in beginning to exercise if you don't already do so. There are other studies that link regular exercise to reduction in estrogen levels - specifically E1.

Here are the studies as reported in Reuters:

Strong exercise may cut breast cancer risk

Last Updated: 2007-02-27 9:48:51 -0400 (Reuters Health)

CHICAGO (Reuters) - Strenuous exercise -- such as lap swimming, aerobics and running -- appears to cut the risk of some breast cancers in women, a study said on Monday.

While it is still not clear how hard or long women need to exercise, the study adds to a growing body of evidence that rigorous activity lowers breast cancer risk.

The team at the University of Southern California in Los Angeles said exercise may reduce cancer risk through changes in metabolism and the immune system, and by reducing weight gain.

The study, appearing in the Archives of Internal Medicine, involved 110,599 women in California whose health histories were tracked from 1995 onward.

Women who said they engaged in strenuous activity for more than five hours a week had a 20 percent lower risk of invasive breast cancer and a 31 percent lower risk of early stage breast cancer, compared to women who participated in less than 30 minutes of such activity every week.

Through 2002, a total of 2,649 of the women were diagnosed with invasive breast cancer, and 593 with early-stage forms of the disease.

The study is the first to look at the cumulative effect of exercise over time, as opposed to women's reports of whether they had exercised shortly before being diagnosed with breast cancer.

"These results provide additional evidence supporting a protective role for long-term strenuous recreational physical activity on risk of invasive and (early stage) breast cancer, whereas the beneficial effects of moderate activity are less clear," the study concluded.

AND

Strenuous exercise lowers lifetime breast cancer risk

Last Updated: 2007-02-21 15:02:14 -0400 (Reuters Health)

By Anne Harding

NEW YORK (Reuters Health) - A new study confirms that for most women, 6 or more hours of strenuous recreational exercise each week can reduce the risk of invasive breast cancer , according to the findings of a new study.

While women with a family history of breast cancer didn't have a reduced risk with exercise, all of the other women did, regardless of how old they were when they started exercising, Dr. Brian L. Sprague of the University of Wisconsin-Madison and colleagues found.

"A lot of women are particularly concerned about breast cancer, and our study just adds more evidence that physical activity is indeed related to breast cancer risk," Sprague told Reuters Health.

His team interviewed 7,630 women who were free of breast cancer, 1,689 with very early-stage or in situ disease, and 6,391 with invasive breast cancer. All of the women ranged in age from 20 to 69.

While there was no link between physical activity and in-situ breast cancer risk, women who reported more than 6 hours of strenuous recreational exercise each week had a 23 percent reduced risk of developing invasive breast cancer compared to women who never exercised.

The reduction in risk was seen women who exercised early in life, after menopause , or in the recent past.

Sprague noted that there were relatively few women in the study with in situ disease, so it may be that the study was not powerful enough to identify a reduced risk with exercise, which other studies have reported. It's possible, he added, that exercise may prevent invasive breast cancer by stopping in situ disease from progressing.

The researchers found no link between physical activity on the job and reduced breast cancer risk. However, Sprague noted, he and his colleagues had to use a fairly crude measurement to gauge occupational activity, based on job titles, so the current study does not necessarily mean on-the-job activity is not protective.

SOURCE: Cancer Epidemiology Biomarkers & Prevention, February 2007.