Impact of primary disease on outcome after allogeneic stem cell transplantation for transformed secondary acute leukaemia

Summary Myelodysplastic syndromes ( MDS ), myeloproliferative neoplasms ( MPN ) and chronic myelomonocytic leukaemia ( CMML ) can progress to secondary acute myeloid leukaemia ( sAML ). We compared the outcome of 4214 sAML patients who received allogeneic haematopoietic stem cell transplantation (allo‐ HSCT ) from an unrelated (62%) or human leucocyte antigen ( HLA )‐identical sibling donor (38%) according the underlying disease: MDS ( n  = 3541), CMML ( n  = 251) or MPN ( n  = 422). After a median follow up of 46·5 months, the estimated 3‐year progression‐free ( PFS ) and overall survival ( OS ) for the entire group was 36% (34–37%) and 41% (40–43%), respectively. The cumulative incidence of relapse and non‐relapse mortality ( NRM ) was 37% (35–39%) and 27% (26–29%), respectively. In a multivariable analysis for OS , besides age ( P  < 0·001), unrelated donor ( P  = 0·011), cytomegalovirus ± constellation ( P  = 0·007), Karnofsky index ≤ 80 ( P  < 0·001), remission status ( P  < 0·001), peripheral blood as stem cell source ( P  = 0·009), sAML from MPN ( P  = 0·003) remained a significant factor in comparison to sAML from MDS , while worse outcome of sAML from CMML did not reach statistical significance ( P  = 0·06). This large registry study demonstrates a major impact of the underlying disease on outcome of sAML after allo‐HSCT.