title: Physical activity and survival after colorectal cancer diagnosis.
abstract: OBJECTIVE
  Physically active individuals have a lower risk of developing colorectal cancer but the influence of exercise on cancer survival is unknown.
  
  
  METHODS
  By a prospective, observational study of 573 women with stage I to III colorectal cancer, we studied colorectal cancer-specific and overall mortality according to predefined physical activity categories before and after diagnosis and by change in activity after diagnosis. To minimize bias by occult recurrences, we excluded women who died within 6 months of their postdiagnosis physical activity assessment.
  
  
  RESULTS
  Increasing levels of exercise after diagnosis of nonmetastatic colorectal cancer reduced cancer-specific mortality (P for trend = .008) and overall mortality (P for trend = .003). Compared with women who engaged in less than 3 metabolic equivalent task [MET] -hours per week of physical activity, those engaging in at least 18 MET-hours per week had an adjusted hazard ratio for colorectal cancer-specific mortality of 0.39 (95% CI, 0.18 to 0.82) and an adjusted hazard ratio for overall mortality of 0.43 (95% CI, 0.25 to 0.74). These results remained unchanged even after excluding women who died within 12 and 24 months of activity assessment. Prediagnosis physical activity was not predictive of mortality. Women who increased their activity (when comparing prediagnosis to postdiagnosis values) had a hazard ratio of 0.48 (95% CI, 0.24 to 0.97) for colorectal cancer deaths and a hazard ratio of 0.51 (95% CI, 0.30 to 0.85) for any-cause death, compared with those with no change in activity.
  
  
  CONCLUSIONS
  Recreational physical activity after the diagnosis of stages I to III colorectal cancer may reduce the risk of colorectal cancer-specific and overall mortality.
authors.affiliation: Division of Medical Oncology, Dana-Farber Cancer Institute, Boston, MA 02115, USA. jmeyerhardt@partners.org
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Meyerhardt
authors.forename: Edward L
authors.initials: EL
authors.lastname: Giovannucci
authors.forename: Michelle D
authors.initials: MD
authors.lastname: Holmes
authors.forename: Andrew T
authors.initials: AT
authors.lastname: Chan
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Chan
authors.forename: Graham A
authors.initials: GA
authors.lastname: Colditz
authors.forename: Charles S
authors.initials: CS
authors.lastname: Fuchs
mesh_terms: D000368:Aged; D015179:Colorectal Neoplasms / Q000175:diagnosis / Q000401:mortality* / Q000473:pathology / Q000628:therapy; D015444:Exercise; D005260:Female; D006801:Humans; D008019:Life Style; D008875:Middle Aged; D009043:Motor Activity; D015999:Multivariate Analysis; D009367:Neoplasm Staging; D009726:Nurses / Q000706:statistics & numerical data; D016017:Odds Ratio; D005082:Physical Exertion; D011446:Prospective Studies; D012307:Risk Factors; D011795:Surveys and Questionnaires; D015996:Survival Rate; D014481:United States / Q000453:epidemiology