title: Providing more up-to-date estimates of patient survival: a comparison of standard survival analysis with period analysis using life-table methods and proportional hazards models.
abstract: OBJECTIVE
  Standard survival methods can yield out-of-date estimates of long-term survival. Period analysis, based on life-table methodology, provides more up-to-date survival estimates by exploring survival during a restricted recent period of interest. It excludes the short-term survival of patients recruited at the start of the study. We use statistical models to further develop the method of period analysis, providing more up-to-date estimates of survival and the ability to explore differences in survival by covariates and adjust for case mix.
  
  
  METHODS
  We use cancer registry data for colorectal cancer in Leicestershire, UK, to illustrate the use of Cox proportional hazards (CPH) models to estimate period and standard survival. We compare these estimates with those obtained using life-table methodology.
  
  
  RESULTS
  Period estimates were slightly higher than the standard estimates as they reflect recent improvements in short-term survival. The results for period analysis using the life-table approach and using CPH models were similar. However, CPH models allowed further investigation of other risk factors and the ability to control for potential confounding variables.
  
  
  CONCLUSIONS
  Using period survival estimates, more up-to-date information is available to clinicians and others with an interest in monitoring survival. Period CHP models offer all the advantages of statistical modeling, and are straightforward to fit in standard statistical packages.
authors.affiliation: Department of Health Sciences, University of Leicester, 22-28 Princess Road West, Leicester, LE1 6TP, UK. lks1@le.ac.uk
authors.forename: Lucy K
authors.initials: LK
authors.lastname: Smith
authors.forename: Paul C
authors.initials: PC
authors.lastname: Lambert
authors.forename: Johannes L
authors.initials: JL
authors.lastname: Botha
authors.forename: David R
authors.initials: DR
authors.lastname: Jones
mesh_terms: D015179:Colorectal Neoplasms / Q000401:mortality; D006801:Humans; D015993:Life Tables; D016016:Proportional Hazards Models; D012042:Registries; D016019:Survival Analysis; D015996:Survival Rate