IntroductionAllogeneic stem cell transplantation (HSCT) is effective treatment for patients with various hematologic disorders. It is, however, a complex, resource-intense and costly procedure. [1][2][3][4] The cost of HSCT has been previously evaluated, mainly in the setting of HLA identical sibling 5 and matched unrelated donor transplants.The first studies on the cost-efficacy of HSCT compared allogeneic HSCT to chemotherapy in patients with acute leukemia. 7,8 Despite the high cost of HSCT, the results demonstrated the advantages of the procedure due to the impact on long-term survival adjusted to the quality of life. In the first published studies, the estimated costs for HSCT varied greatly (Online Supplementary Table S1) depending on the country in which they were performed, type of donor, transplant center procedures and year of transplantation. 5,7,[9][10][11] A more recent comparative study of autologous and allogeneic HSCT for patients transplanted for hematologic malignancies in the USA estimated a 100-day total cost of US$ 203,026 for allogeneic HSCT. 12 Unrelated donor cord blood transplantation (UCBT) has become a widely accepted transplant modality in the absence of an HLA-matched donor. [13][14][15][16] However, the delay of engraftment and the increased risk of graft failure remain problems in adults transplanted with a single cord blood unit. The possibility of using two cord blood units has extended the use of UCBT to patients for whom a single unit containing a minimum of 2.5x10 7 /kg total nucleated cells is not available. [17][18][19] Studies have been performed comparing outcomes after single (s) UCBT and double (d) UCBT,20 but, none focused on a homo- open-access paper. doi:10.3324/haematol.2013.092254 The online version of this article has a Supplementary Appendix. Manuscript received on May 27, 2013. Manuscript accepted on October 14, 2013 Double cord blood transplantation extends the use of cord blood to adults for whom a single unit is not available, but the procedure is limited by its cost. To evaluate outcomes and cost-effectiveness of double compared to single cord blood transplantation, we analyzed 134 transplants in adults with acute leukemia in first remission. Transplants were performed in France with reduced intensity or myeloablative conditioning regimens. Costs were estimated from donor search to 1 year after transplantation. A Markov decision analysis model was used to calculate qualityadjusted life-years and cost-effectiveness ratio within 4 years. The overall survival at 2 years after single and double cord blood transplants was 42% versus 62%, respectively (P=0.03), while the leukemia-free-survival was 33% versus 53%, respectively (P=0.03). The relapse rate was 21% after double transplants and 42% after a single transplant (P=0.006). No difference was observed for non-relapse mortality or chronic graft-versus-host-disease. The estimated costs up to 1 year after reduced intensity conditioning for single and double cord blood transplantation were € 165,253 and €191,...