Journal of the National Cancer Institute Advance Access originally published online on April 28, 2009
JNCI Journal of the National Cancer Institute 2009 101(9):630-643; doi:10.1093/jnci/djp068
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Published by Oxford University Press 2009.
COMMENTARY |
Physical Activity, Weight Control, and Breast Cancer Risk and Survival: Clinical Trial Rationale and Design Considerations
Affiliations of authors: Applied Research Program, Division of Cancer Control and Population Sciences (RB-B), Biometric Research Branch, Division of Cancer Treatment (SH), and Nutrition Epidemiology Branch, Division of Cancer Epidemiology and Genetics (AS), National Cancer Institute, National Institutes of Health, Bethesda, MD; Scientific Operations, Susan G. Komen for the Cure, Dallas, TX (MHA); Department of Exercise Sciences, University of South Carolina, Columbia, SC (SNB); Department of Medicine, University of Toronto, Mount Sinai Hospital, Toronto, CA (PJG); Cancer Prevention Program, Fred Hutchinson Cancer Research Center, Seattle, WA (AMT); Centers for Behavioral and Preventive Medicine, The Miriam Hospital and Brown University, Providence, RI (RW)
Correspondence to: Rachel Ballard-Barbash, PhD, Applied Research Program, Division of Cancer Control and Population Sciences, National Cancer Institute, National Institutes of Health, EPN 4005, Executive Blvd, Bethesda, MD 20892-7344 (e-mail: barbashr{at}mail.nih.gov).
Substantial observational epidemiological evidence exists that physical activity and weight control are associated with decreased risk of postmenopausal breast cancer. Uncertainty remains regarding several aspects of these associations, including the effect of possible confounding factors on these associations. We present the rationale and design for two randomized controlled trials that can help resolve this uncertainty. In a 5-year prevention trial conducted among women at high risk of breast cancer, the primary endpoint would be breast cancer incidence. For a comparable survivorship trial, the primary endpoint would be the disease-free interval and secondary endpoints would be breast cancer recurrence–free interval, second primary breast cancer, and total invasive plus in situ breast cancer. A set of inclusion and exclusion criteria is proposed for both trials. Intervention goals are the same for both trials. Goals for the weight control intervention would be, for women whose body mass index (BMI) is greater than 25 kg/m2, to lose 10% of body weight and, for women whose BMI is less than or equal to 25 kg/m2, to avoid weight gain. The goal for the physical activity intervention would be to achieve and maintain regular participation in a moderate-intensity physical activity program for a total of 150–225 minutes over at least 5 days per week. Sample size calculations are based on alternative assumptions about hazard ratio, adherence, follow-up duration, and power and are presented for the primary prevention and survivorship trials. Although both studies could enhance our understanding of breast cancer etiology and benefit public health, practical considerations, including smaller sample size, ease of recruitment, and reduced likelihood of early termination, favor the survivorship trial at this time.
Manuscript received September 2, 2008; revised January 29, 2009; accepted February 27, 2009.
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