title: Risk of cancer after blood transfusion from donors with subclinical cancer: a retrospective cohort study.
abstract: BACKGROUND
  Although mechanisms for detection of short-term complications after blood transfusions are well developed, complications with delayed onset, notably transmission of chronic diseases such as cancer, have been difficult to assess. Our aim was to investigate the possible risk of cancer transmission from blood donors to recipients through blood transfusion.
  
  
  METHODS
  We did a register-based retrospective cohort study of cancer incidence among patients who received blood from donors deemed to have a subclinical cancer at the time of donation. These precancerous donors were diagnosed with a cancer within 5 years of the donation. Data from all computerised blood bank registers in Sweden and Denmark gathered between 1968 and 2002 were merged into a common database. Demographic and medical data, including mortality and cancer incidence, were ascertained through linkages with nationwide, and essentially complete, population and health-care registers. The risk of cancer in exposed recipients relative to that in recipients who received blood from non-cancerous donors was estimated with multivariate Poisson regression, adjusting for potential confounding factors.
  
  
  RESULTS
  Of the 354 094 transfusion recipients eligible for this analysis, 12,012 (3%) were exposed to blood products from precancerous donors. There was no excess risk of cancer overall (adjusted relative risk 1.00, 95% CI 0.94-1.07) or in crude anatomical subsites among recipients of blood from precancerous donors compared with recipients of blood from non-cancerous donors.
  
  
  CONCLUSIONS
  Our data provide no evidence that blood transfusions from precancerous blood donors are associated with increased risk of cancer among recipients compared with transfusions from non-cancerous donors.
authors.affiliation: Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Gustaf
authors.initials: G
authors.lastname: Edgren
authors.forename: Henrik
authors.initials: H
authors.lastname: Hjalgrim
authors.forename: Marie
authors.initials: M
authors.lastname: Reilly
authors.forename: Trung Nam
authors.initials: TN
authors.lastname: Tran
authors.forename: Klaus
authors.initials: K
authors.lastname: Rostgaard
authors.forename: Agneta
authors.initials: A
authors.lastname: Shanwell
authors.forename: Kjell
authors.initials: K
authors.lastname: Titlestad
authors.forename: Johanna
authors.initials: J
authors.lastname: Adami
authors.forename: Agneta
authors.initials: A
authors.lastname: Wikman
authors.forename: Casper
authors.initials: C
authors.lastname: Jersild
authors.forename: Gloria
authors.initials: G
authors.lastname: Gridley
authors.forename: Louise
authors.initials: L
authors.lastname: Wideroff
authors.forename: Olof
authors.initials: O
authors.lastname: Nyrén
authors.forename: Mads
authors.initials: M
authors.lastname: Melbye
mesh_terms: D015331:Cohort Studies; D003718:Denmark; D005260:Female; D006801:Humans; D008297:Male; D009369:Neoplasms / Q000209:etiology*; D012042:Registries; D012189:Retrospective Studies; D012307:Risk Factors; D013548:Sweden; D065227:Transfusion Reaction