Los Angeles, Feb. 26, 2007 - Significant findings have emerged from the California Teachers Study (CTS) that suggest long-term recreational physical activity plays a protective role against invasive and in situ breast cancer.
"Previous studies have linked physical activity with a reduction in breast cancer, but few studies have examined risk separately for in situ and invasive breast cancers or have characterized risk by hormone receptor status," said Leslie Bernstein, professor of preventive medicine at the Keck School of Medicine of USC and primary investigator of the CTS. "This study is unique because it provides the first prospective study data documenting that a woman's long-term exercise habits are important in determining her future breast cancer risk."
In a study to be published in the February 26 issue of the Archives of Internal Medicine, researchers analyzed data collected from a cohort of 110,599 women who were current or former California teachers and public school professionals with no prior history of breast cancer, and who were between the ages of 22 and 79 years at the start of the study. The study was initiated in 1995 with detailed collection of information on women's exercise histories and current exercise habits.
The study focused on the impact of strenuous activities, as well as moderate activities, collecting information on the amount each woman exercised per week from high school through age 54 years (or the woman's current age if she was younger than 54). Women were followed through the end of 2002 using information from California's statewide comprehensive cancer registry to identify which women developed breast cancer. During the 6.5 year follow-up period, 2,649 women were diagnosed with invasive breast cancer and 593 were diagnosed with in situ breast cancer, meaning the cancer was confined to the ducts or lobules of the breast.