title: Accuracy of cause of death data routinely recorded in a population-based cancer registry: impact on cause-specific survival and validation using the Geneva Cancer Registry.
abstract: BACKGROUND
  Information on the underlying cause of death of cancer patients is of interest because it can be used to estimate net survival. The population-based Geneva Cancer Registry is unique because registrars are able to review the official cause of death. This study aims to describe the difference between the official and revised cause-of-death variables and the impact on cancer survival estimates.
  
  
  METHODS
  The recording process for each cause of death variable is summarised. We describe the differences between the two cause-of-death variables for the 5,065 deceased patients out of the 10,534 women diagnosed with breast cancer between 1970 and 2009. The Kappa statistic and logistic regression are applied to evaluate the degree of concordance. The impact of discordance on cause-specific survival is examined using the Kaplan Meier method.
  
  
  RESULTS
  The overall agreement between the two variables was high. However, several subgroups presented a lower concordance, suggesting differences in calendar time and less attention given to older patients and more advanced diseases. Similarly, the impact of discordance on cause-specific survival was small on overall survival but larger for several subgroups.
  
  
  CONCLUSIONS
  Estimation of cancer-specific survival could therefore be prone to bias when using the official cause of death. Breast cancer is not the more lethal cancer and our results can certainly not be generalised to more lethal tumours.
authors.affiliation: Geneva Cancer Registry, Institute for Social and Preventive Medicine, University of Geneva, 55 Boulevard de la Cluse, Geneva, 1205, Switzerland. robin.schaffar@lshtm.ac.uk.
authors.forename: Robin
authors.initials: R
authors.lastname: Schaffar
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Rapiti
authors.forename: Bernard
authors.initials: B
authors.lastname: Rachet
authors.forename: Laura
authors.initials: L
authors.lastname: Woods
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001943:Breast Neoplasms / Q000453:epidemiology* / Q000401:mortality / Q000473:pathology / Q000628:therapy; D002423:Cause of Death; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008875:Middle Aged; D009367:Neoplasm Staging; D011159:Population Surveillance; D012042:Registries; D012307:Risk Factors; D055815:Young Adult