Keep physically active to avoid breast cancer

Reported by Susan Aldridge, PhD, medical journalist

A new study shows that long-term exercise can protect women against breast cancer.
Previous studies have suggested that exercise can protect against breast cancer. Now a new report from the California Teachers Study looks at the impact of long-term exercise on the risk of various types of breast cancer. The report collected data from over 110,000 female teaching professionals in California and began in 1995, with a detailed study of the women's exercise histories and current exercise habits.

During six and a half years of follow up, 2,649 women were diagnosed with invasive breast cancer and 593 with in situ cancer - disease confined to the ducts or lobules of the breast. Invasive breast cancer risk was reduced among women participating in strenuous activity, such as swimming, jogging or aerobics, for more than five hours a week, compared to the least active women. A similar link was found for in situ breast cancer. One surprising finding was that the benefit of long-term exercise was seen only among those with estrogen-negative tumors. Previous research has not uncovered differences in the benefit of exercise with hormone status of a breast cancer. Drugs like tamoxifen and raloxifene protect against hormone positive breast cancer, but not hormone negative cancers. It seems, from these findings, that exercise might fulfil this protective role.

Source
Archives of Internal Medicine 26th February 2007 Volume 167 Number 4

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