title: Physical activity before and after breast cancer diagnosis and survival - the Norwegian women and cancer cohort study.
abstract: BACKGROUND
  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. Our study will add to the knowledge on whether a modifiable behavior such as PA can improve survival.
  
  
  METHODS
  We 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.
  
  
  RESULTS
  Pre-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.
  
  
  CONCLUSIONS
  Overall, 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.
authors.affiliation: Department of Community Medicine, Faculty of Health Sciences, University of Tromsø, The Arctic University of Norway, 9037, Tromsø, Norway. kristin.benjaminsen.borch@uit.no.
authors.forename: Kristin Benjaminsen
authors.initials: KB
authors.lastname: Borch
authors.affiliation: Department of Community Medicine, Faculty of Health Sciences, University of Tromsø, The Arctic University of Norway, 9037, Tromsø, Norway. Tonje.braaten@uit.no.
authors.forename: Tonje
authors.initials: T
authors.lastname: Braaten
authors.affiliation: Department of Community Medicine, Faculty of Health Sciences, University of Tromsø, The Arctic University of Norway, 9037, Tromsø, Norway. Eiliv.lund@uit.no.
authors.forename: Eiliv
authors.initials: E
authors.lastname: Lund
authors.affiliation: Department of Community Medicine, Faculty of Health Sciences, University of Tromsø, The Arctic University of Norway, 9037, Tromsø, Norway. Elisabete.Weiderpass.Vainio@ki.se.|Department of Research. Cancer Registry of Norway, Institute of Population-Based Cancer Research, 5313 Majorstuen, 0304, Oslo, Norway. Elisabete.Weiderpass.Vainio@ki.se.|Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, 171 77, Stockholm, Sweden. Elisabete.Weiderpass.Vainio@ki.se.|Genetic Epidemiology Group, Folkhälsan Research Center, University of Helsinki, Biomedicum 1, Haartmansgatan 8, PB 63, FI-00014, Helsinki, Finland. Elisabete.Weiderpass.Vainio@ki.se.
authors.forename: Elisabete
authors.initials: E
authors.lastname: Weiderpass
mesh_terms: D000328:Adult; D000368:Aged; D001943:Breast Neoplasms / Q000401:mortality*; D015331:Cohort Studies; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D008875:Middle Aged; D009043:Motor Activity / Q000502:physiology; D009664:Norway / Q000453:epidemiology; D011795:Surveys and Questionnaires