Lifetime moderate-to-vigorous physical activity and ER/PR/HER-defined post-menopausal breast cancer risk

Abstract

Purpose

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.

Methods

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.

Results

Total lifetime leisure-time MVPA was associated with reduced risk of ER−/PR− breast cancer in a dose–response fashion (p _trend = 0.014). In contrast, total lifetime household MVPA was associated with reduced risk of ER+ and/or PR+ breast cancer (p _trend < 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.

Conclusions

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.

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