Abstract
BackgroundEvidence has accumulated showing that recreational physical activity reduces breast cancer risk. However, it is unclear whether risk reduction pertains to specific receptor-defined subtypes. Moreover, few studies have examined whether changes in the amount of recreational physical activity during adulthood influence breast cancer risk.MethodsA total of 108,907 women, ages 22 to 79 years with no history of breast cancer when joining the California Teachers Study in 1995–1996, completed a baseline questionnaire and were eligible for the study. Through 2012, 5882 women were diagnosed with invasive breast cancer. Breast cancer subtypes were defined by the expression status of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2). Multivariable Cox proportional hazards models provided adjusted hazard ratios (HRs) and 95 % confidence intervals (CIs) for breast cancer overall and ER/PR/HER2-defined subtypes associated with long-term (from high school through age 54 or age at cohort entry, whichever was younger) and baseline (during 3 years prior to baseline) recreational physical activity. Among women who also completed a follow-up questionnaire at 10 years after baseline in 2005–2008 (54,686 women, 1406 with invasive breast cancer), risk associated with changes in the amount of recreational physical activity from baseline to the 10-year follow-up (during 3 years prior to the 10-year follow-up) was determined.ResultsBoth long-term and baseline strenuous recreational physical activity were inversely associated with risk of invasive breast cancer (Ptrend ≤0.03). The observed associations were mainly confined to women with triple negative breast cancer (TNBC, ER–/PR–/HER2–, Ptrend ≤0.02) or luminal A-like subtype (ER+ or PR+ plus HER2–) who were former users of menopausal hormone therapy at baseline (Ptrend = 0.02, Phomogeneity of trends ≤0.03). Moreover, women who consistently engaged in the highest level (≥3.51 h/wk/y) of strenuous recreational physical activity between baseline and 10-year follow-up had the lowest risk of breast cancer (HR = 0.71, 95 % CI = 0.52–0.98) when compared to those who were consistently low (≤0.50 h/wk/y).ConclusionsStrenuous recreational physical activity is associated with lower breast cancer risk, especially TNBC. The benefit may be maximized by consistently engaging in high-intensity recreational physical activity during adulthood.Electronic supplementary materialThe online version of this article (doi:10.1186/s13058-016-0723-3) contains supplementary material, which is available to authorized users.
Highlights
Evidence has accumulated showing that recreational physical activity reduces breast cancer risk
In the California Teachers Study (CTS), which has actively followed female California public school professionals for incidence of cancer and other outcomes since 1995, we previously reported that increased strenuous recreational physical activity, but not moderate intensity recreational physical activity, was associated with reduced risk of invasive breast cancer; the association was confined to estrogen receptor (ER)-negative (ER–) as well as ER–/progesterone receptor (PR)– invasive breast cancer in the analyses for ERdefined or ER/PR-defined subtypes [3]
We assess risk of invasive breast cancer overall and by ER/PR/human epidermal growth factor receptor 2 (HER2)-defined subtypes associated with long-term and baseline total, strenuous intensity, and moderate intensity recreational physical activity using CTS data from baseline through December, 2012
Summary
Evidence has accumulated showing that recreational physical activity reduces breast cancer risk. Previous epidemiologic studies showed that the most active women had, on average, a 25–30 % lower breast cancer risk than women in the lowest category of recreational physical activity [2]. It is unclear whether increased recreational physical activity protects against the development of all breast cancers or only certain breast cancer subtypes as defined by the expression status of the estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2). Only the Women’s Health Initiative Cohort Study [4] and two case-control studies [5, 6] have investigated the association between recreational physical activity and TNBC risk
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
