title: Perioperative allogeneic blood transfusion does not cause adverse sequelae in patients with cancer: a meta-analysis of unconfounded studies.
abstract: BACKGROUND
  There is controversy over whether perioperative allogeneic red blood cell transfusions are associated with an increased risk of cancer recurrence, postoperative infection or death in patients with cancer undergoing surgery.
  
  
  METHODS
  A systematic meta-analysis was performed to answer this question. Studies were identified from electronic databases (Medline 1966-1997, Cancerlit 1983-1997, Current Contents, Cinahl 1982-1996, Healthstar 1990-1997, Bioabstracts 1990-1996 and Embase), by hand search of the bibliographies of identified studies and relevant journals, and by contact with experts in the field. All randomized controlled trials or prospective cohort studies with active comparator controls (autologous or leucocyte-depleted allogeneic blood) were eligible for inclusion if they reported on mortality, infection or recurrence rate in patients with cancer undergoing potentially curative surgical resection. The validity of the identified studies was assessed by means of a standardized scale, and data abstraction was carried out by two investigators independently. A random effects model was used for data synthesis.
  
  
  RESULTS
  Of the 2172 references identified, only 17 studies fulfilled the inclusion criteria. After exclusion of duplicate publications, six randomized controlled trials and two prospective cohort studies with appropriate concurrent controls were included in the analysis. The summary risk ratios were 0.95 (95 per cent confidence interval (c.i.) 0.79-1.15) for all-cause mortality and 1.06 (95 per cent c.i. 0.88-1.28) for cancer recurrence, the two endpoints that were appropriate to combine statistically. There was significant heterogeneity (explainable by differences in study design and patient characteristics) in the postoperative infection data and the summary risk ratio was 1.00 (95 per cent c.i. 0.76-1.32) for the four studies that were appropriate to subject to meta-analysis. Given the sample sizes of these eight studies, this meta-analysis had insufficient power to detect a relative difference of less than 20 per cent in the frequency of death, cancer recurrence or infection between the allogeneic and control transfusion arms.
  
  
  CONCLUSIONS
  Although more studies are required before a definitive statement can be made, at this time there is no evidence that allogeneic blood transfusion increases the risk of clinically important adverse sequelae in patients with cancer undergoing surgery.
authors.affiliation: Division of General Internal Medicine, Loeb Medical Research Center, Ottawa Civic Hospital, Ontario, Canada.
authors.forename: F A
authors.initials: FA
authors.lastname: McAlister
authors.forename: H D
authors.initials: HD
authors.lastname: Clark
authors.forename: P S
authors.initials: PS
authors.lastname: Wells
authors.forename: A
authors.initials: A
authors.lastname: Laupacis
mesh_terms: D015331:Cohort Studies; D006801:Humans; D007239:Infections / Q000209:etiology*; D007430:Intraoperative Care; D009364:Neoplasm Recurrence, Local / Q000209:etiology*; D009369:Neoplasms / Q000601:surgery*; D011183:Postoperative Complications / Q000209:etiology*; D011446:Prospective Studies; D016032:Randomized Controlled Trials as Topic; D012307:Risk Factors; D012680:Sensitivity and Specificity; D065227:Transfusion Reaction; D014184:Transplantation, Homologous