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Effects of exercise dose on endogenous estrogens in postmenopausal women: a randomized trial.

Department of Cancer Epidemiology and Prevention ResearchCancerControl Alberta, Alberta Health Services, 2210 2nd Street Southwest, Calgary, Alberta, Canada T2S 3C3Departments of Oncology and Community Health SciencesCumming School of Medicine, University of Calgary, Calgary, Alberta, CanadaKeck School of MedicineUniversity of Southern California, Los Angeles, California, USASchool of Public HealthUniversity of Alberta, Edmonton, Alberta, CanadaCross Cancer InstituteCancerControl Alberta, Alberta Health Services, Edmonton, Alberta, CanadaFaculty of Physical Education and RecreationUniversity of Alberta, Edmonton, Alberta, Canada Department of Cancer Epidemiology and Prevention ResearchCancerControl Alberta, Alberta Health Services, 2210 2nd Street Southwest, Calgary, Alberta, Canada T2S 3C3Departments of Oncology and Community Health SciencesCumming School of Medicine, University of Calgary, Calgary, Alberta, CanadaKeck School of MedicineUniversity of Southern California, Los Angeles, California, USASchool of Public HealthUniversity of Alberta, Edmonton, Alberta, CanadaCross Cancer InstituteCancerControl Alberta, Alberta Health Services, Edmonton, Alberta, CanadaFaculty of Physical Education and RecreationUniversity of Alberta, Edmonton, Alberta, Canada christine.friedenreich@albertahealthservices.ca. Department of Cancer Epidemiology and Prevention ResearchCancerControl Alberta, Alberta Health Services, 2210 2nd Street Southwest, Calgary, Alberta, Canada T2S 3C3Departments of Oncology and Community Health SciencesCumming School of Medicine, University of Calgary, Calgary, Alberta, CanadaKeck School of MedicineUniversity of Southern California, Los Angeles, California, USASchool of Public HealthUniversity of Alberta, Edmonton, Alberta, CanadaCross Cancer InstituteCancerControl Alberta, Alberta Health Services, Edmonton, Alberta, CanadaFaculty of Physical Education and RecreationUniversity of Alberta, Edmonton, Alberta, Canada.

Endocrine-related cancer. 2015;(5):863-76
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Abstract

Exercise dose comparison trials with biomarker outcomes can identify the amount of exercise required to reduce breast cancer risk and also strengthen the causal inference between physical activity and breast cancer. The Breast Cancer and Exercise Trial in Alberta (BETA) tested whether or not greater changes in estradiol (E2), estrone, and sex hormone-binding globulin (SHBG) concentrations can be achieved in postmenopausal women randomized to 12 months of HIGH (300 min/week) vs MODERATE (150 min/week) volumes of aerobic exercise. BETA included 400 inactive postmenopausal women aged 50-74 years with BMI of 22-40 kg/m(2). Blood was drawn at baseline and 6 and 12 months. Adiposity, physical fitness, diet, and total physical activity were assessed at baseline and 12 months. Intention-to-treat analyses were performed using linear mixed models. At full prescription, women exercised more in the HIGH vs MODERATE group (median min/week (quartiles 1,3): 253 (157 289) vs 137 (111 150); P<0.0001). Twelve-month changes in estrogens and SHBG were <10% on average for both groups. No group differences were found for E2, estrone, SHBG or free E2 changes (treatment effect ratios (95% CI) from linear mixed models: 1.00 (0.96-1.06), 1.02 (0.98-1.05), 0.99 (0.96-1.02), 1.01 (0.95, 1.06), respectively, representing the HIGHMODERATE ratio of geometric mean biomarker levels over 12 months; n=382). In per-protocol analyses, borderline significantly greater decreases in total and free E2 occurred in the HIGH group. Overall, no dose effect was observed for women randomized to 300 vs 150 min/week of moderate to vigorous intensity exercise who actually performed a median of 253 vs 137 min/week. For total and free E2, the lack of differential effect may be due to modest adherence in the higher dose group.

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