Lifetime moderate-to-vigorous physical activity and ER/PR/HER-defined post-menopausal breast cancer risk
To assess the relationship of moderate-to-vigorous physical activity (MVPA) in leisure-time, household, and occupational domains across the total lifetime and in four age periods with breast cancer risk, as defined by estrogen receptor (ER)/progesterone receptor (PR) status and ER/PR/human epidermal growth factor-2 (HER2) status, among post-menopausal women.
Data were from 692 women with incident breast cancer and 644 controls in the Canadian Breast Cancer Study, a case–control study of women aged 40–80 years in British Columbia and Ontario. Mean metabolic equivalent (MET)-hours/week for questionnaire-assessed leisure-time, household, and occupational MVPA were calculated for the total lifetime and four age periods (12–17, 18–34, 45–49, and ≥50 years). Odds ratios (ORs) for the relationships between domain-specific MVPA at each lifetime period and risks of ER/PR-defined and ER/PR/HER2-defined breast cancers were estimated using polytomous logistic regression. Trend tests for dose–response relationships were calculated for the ORs across increasing tertiles of mean MET-hours/week of MVPA.
Total lifetime leisure-time MVPA was associated with reduced risk of ER−/PR− breast cancer in a dose–response fashion (ptrend = 0.014). In contrast, total lifetime household MVPA was associated with reduced risk of ER+ and/or PR+ breast cancer (ptrend < 0.001). When further stratified by HER2 status, the effect of leisure-time MVPA appeared confined to HER2− breast cancers, and the effect of household MVPA did not differ according to HER2 status. Similar trends were observed when stratified by age period.
Lifetime leisure-time MVPA appeared to be associated with reduced risk of ER−/PR−/HER2− breast cancers and lifetime household MVPA was associated with reduced risk of ER+ and/or PR+ breast cancer, regardless of HER2 status.
KeywordsPhysical activity Breast cancer Estrogen Progesterone HER2
The authors thank all study participants and several co-investigators, collaborators, and staff, particularly Agnes Lai. This research was originally part of Dr. Lindsay Kobayashi’s MSc thesis, which was supported by an Ontario Graduate Scholarship from the Ontario Ministry of Training, Colleges, and Universities and a studentship from the Queen’s University Terry Fox Foundation Training Program in Transdisciplinary Cancer Research in Partnership with CIHR.
This research was funded by an operating grant from the Canadian Institutes of Health Research (Grant #69036).
Compliance with ethical standards
Conflict of interest
All authors declare no conflict of interest.
All procedures performed in the study were in accordance with the ethical standards of the University of British Columbia/BC Cancer Agency Research Ethics Board, the Queen’s University Health Sciences Research Ethics Board, and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
Informed consent was obtained from all individual participants included in the study.
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