Open AccessReduced risk of breast cancer associated with recreational physical activity varies by HER 2 status
Author(s) -
Ma Huiyan,
Xu Xinxin,
Ursin Giske,
Simon Michael S.,
Marchbanks Polly A.,
Malone Kathleen E.,
Lu Yani,
McDonald Jill A.,
Folger Suzanne G.,
Weiss Linda K.,
SullivanHalley Jane,
Deapen Dennis M.,
Press Michael F.,
Bernstein Leslie
Publication year - 2015
Publication title -
cancer medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.403
H-Index - 53
ISSN - 2045-7634
DOI - 10.1002/cam4.465
Subject(s) - breast cancer , medicine , oncology , menarche , biomarker , estrogen receptor , population , logistic regression , cancer , demography , metabolic equivalent , physical activity , physiology , gynecology , environmental health , biology , physical therapy , biochemistry , sociology
Convincing epidemiologic evidence indicates that physical activity is inversely associated with breast cancer risk. Whether this association varies by the tumor protein expression status of the estrogen receptor ( ER ), progesterone receptor ( PR ), human epidermal growth factor receptor 2 ( HER 2), or p53 is unclear. We evaluated the effects of recreational physical activity on risk of invasive breast cancer classified by the four biomarkers, fitting multivariable unconditional logistic regression models to data from 1195 case and 2012 control participants in the population‐based Women's Contraceptive and Reproductive Experiences Study. Self‐reported recreational physical activity at different life periods was measured as average annual metabolic equivalents of energy expenditure [ MET ]‐hours per week. Our biomarker‐specific analyses showed that lifetime recreational physical activity was negatively associated with the risks of ER ‐positive ( ER +) and of HER 2‐negative ( HER 2−) subtypes (both P trend ≤ 0.04), but not with other subtypes (all P trend > 0.10). Analyses using combinations of biomarkers indicated that risk of invasive breast cancer varied only by HER 2 status. Risk of HER 2–breast cancer decreased with increasing number of MET ‐hours of recreational physical activity in each specific life period examined, although some trend tests were only marginally statistically significant (all P trend ≤ 0.06). The test for homogeneity of trends ( HER 2– vs. HER 2+ ) reached statistical significance only when evaluating physical activity during the first 10 years after menarche ( P homogeneity = 0.03). Our data suggest that physical activity reduces risk of invasive breast cancers that lack HER 2 overexpression, increasing our understanding of the biological mechanisms by which physical activity acts.