Abstract
BackgroundThe main aim of this study was to investigate pre- and post-diagnostic physical activity (PA) levels, as well as changes in pre- and post-diagnostic PA levels, and their association with all-cause and breast cancer-specific mortality in women with breast cancer. Our study will add to the knowledge on whether a modifiable behavior such as PA can improve survival.MethodsWe included 1,327 women with breast cancer from the population-based Norwegian Women and Cancer study, which enrolled women from 1991 to 2003. Breast cancer cases were identified through linkage to the Cancer Registry of Norway; date and cause of death were obtained from the National Register for Causes of Death through 31 December 2012. Self-reported pre- and post-diagnostic PA levels were assessed, and Cox proportional hazard regression and spline regression were used to evaluate the associations.ResultsPre-diagnostic PA levels were not associated with all-cause or breast cancer-specific mortality. Post-diagnostic PA levels were associated with a significant trend (P < 0.001) of decreased all-cause and breast cancer-specific mortality, which was stronger among older women (aged 50–74 years) and did not differ across categories of body mass index. All-cause mortality (hazard ratio [HR] = 1.76, 95 % confidence interval [CI] 1.21–2.56) and breast cancer-specific mortality (HR = 2.05, 95 % CI 1.35–3.10) increased among women who reduced their post-diagnostic PA level. These values were similar among women whose maintained an inactive PA level pre- and post-diagnosis.ConclusionOverall, we observed a dose–response trend, with an inverse association between increased post-diagnostic PA level and all-cause and breast cancer-specific mortality, as well as a higher mortality risk among women who reduced their post-diagnostic PA levels. Our results are very promising for women with breast cancer, and indicate that health care professionals should consider adding PA as a part of primary cancer treatment.Electronic supplementary materialThe online version of this article (doi:10.1186/s12885-015-1971-9) contains supplementary material, which is available to authorized users.
Highlights
The main aim of this study was to investigate pre- and post-diagnostic physical activity (PA) levels, as well as changes in pre- and post-diagnostic PA levels, and their association with all-cause and breast cancer-specific mortality in women with breast cancer
Data from the Breast Cancer Pooling Project indicated that engagement in at least 10 metabolic equivalent (MET)-h/week of PA was associated with a 27 % reduction in all-cause mortality and a 25 % reduction in breast cancer-specific mortality among breast cancer survivors [10]
It is import to understand whether increasing PA after cancer diagnosis is beneficial for breast cancer survivors, and if increased post-diagnostic PA can improve survival
Summary
The main aim of this study was to investigate pre- and post-diagnostic physical activity (PA) levels, as well as changes in pre- and post-diagnostic PA levels, and their association with all-cause and breast cancer-specific mortality in women with breast cancer. PA may decrease breast cancer recurrence and extend overall breast cancer survival and disease-free breast cancer survival [5,6,7,8] In their recently released report, the Continuous Update Project of the World Cancer Research Fund concluded. Borch et al BMC Cancer (2015) 15:967 that there is limited evidence for an association between pre-diagnostic and post-diagnostic PA levels and all-cause and breast cancer-specific mortality among women with breast cancer [9]. A recent meta-analysis included 49,095 breast cancer survivors and reported a 23 % decreased relative risk of all-cause and breast cancer-specific mortality with increased PA levels [6]. It is import to understand whether increasing PA after cancer diagnosis is beneficial for breast cancer survivors, and if increased post-diagnostic PA can improve survival
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