Originally published as JCO Early Release 10.1200/JCO.2009.24.9557 on February 16 2010

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Alberta Physical Activity and Breast Cancer Prevention Trial: Sex Hormone Changes in a Year-Long Exercise Intervention Among Postmenopausal Women

From Alberta Health Services; Department of Medicine, University of Calgary, Calgary; Cross Cancer Institute, Alberta Health Services; Departments of Public Health Sciences, Physical Therapy, and Oncology and Faculty of Physical Education and Recreation, University of Alberta, Edmonton, Alberta; Departments of Statistics and Physical Therapy, University of British Columbia, Vancouver, British Columbia; Campbell Family Institute for Breast Cancer Research, Ontario Cancer Institute; Sunnybrook Research Institute, Toronto, Ontario, Canada; Cancer Research Center of Hawai'i, University of Hawai'i, Honolulu, HI; Fred Hutchinson Cancer Research Center, Seattle, WA; Division of Cancer Control and Population Sciences, National Cancer Institute, Bethesda, MD; School of Medicine, University of Southern California, Los Angeles, CA; Department of Epidemiology and Public Health, Yale University, New Haven, CT; and Department of Exercise and Sports Science, East Carolina University, Greenville, NC.

Corresponding author: Christine M. Friedenreich, PhD, Alberta Health Services, Calgary, Alberta, Canada, T2N 4N2; e-mail: christine.friedenreich{at}albertahealthservices.ca.

Purpose We examined how an aerobic exercise intervention influenced circulating estradiol, estrone, sex hormone–binding globulin (SHBG), androstenedione, and testosterone levels, which may be involved in the association between physical activity and breast cancer risk.

Methods A two-center, two-arm randomized controlled trial of exercise was conducted in 320 postmenopausal, sedentary women age 50 to 74 years. Participants were randomly assigned to a 1-year aerobic exercise intervention of 225 min/wk (n = 160) or to a control group who maintained their usual level of activity (n = 160). Baseline, 6-month, and 12-month assessments of estrone, estradiol, androstenedione, and testosterone were quantified by radioimmunoassay after extraction, and SHBG was quantified by an immunometric assay. Intent-to-treat analyses were performed using linear mixed models.

Results Blood data were available on 309 women (96.6%) at 12 months. Women in the intervention group exercised an average of 3.6 d/wk for 178 min/wk. At 12 months, statistically significant reductions in estradiol (treatment effect ratio [TER] = 0.93; 95% CI, 0.88 to 0.98) and free estradiol (TER = 0.91; 95% CI, 0.87 to 0.96) and increases in SHBG (TER = 1.04; 95% CI, 1.02 to 1.07) were observed in the exercise group compared with the control group. No significant differences in estrone, androstenedione, and testosterone levels were observed between exercisers and controls at 12 months.

Conclusion This trial found that previously sedentary postmenopausal women can adhere to a moderate- to vigorous-intensity exercise program that results in changes in estradiol and SHBG concentrations that are consistent with a lower risk for postmenopausal breast cancer.

See accompanying editorial on page 1445

Supported by Research Grant No. 017468 from the Canadian Breast Cancer Research Alliance. C.M.F. is supported by career awards from the Canadian Institutes of Health Research and the Alberta Heritage Foundation for Medical Research. K.S.C. is supported by the Canada Research Chairs Program.

Authors' disclosures of potential conflicts of interest and author contributions are found at the end of this article.

Clinical trial information can be found for the following: NCT00522262 [ClinicalTrials.gov] .

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