Hematopoietic stem cell transplantation for paroxysmal nocturnal hemoglobinuria: long-term results of a retrospective study on behalf of the Gruppo Italiano Trapianto Midollo Osseo (GITMO).

BACKGROUND Paroxysmal nocturnal hemoglobinuria is an acquired clonal disorder of the hemopoietic stem cells for which the only curative treatment is allogeneic hematopoietic stem cell transplantation. DESIGN AND METHODS The aim of this retrospective study was to assess the long-term clinical and hematologic results in 26 paroxysmal nocturnal hemoglobinuria patients who received hematopoietic stem cell transplantation in Italy between 1988 and 2006. The patients were aged 22 to 60 years (median 32 years). Twenty-three donors were HLA-identical (22 siblings and one unrelated) and 3 were HLA-mismatched (2 related and one unrelated). RESULTS Fifteen patients received a myeloablative conditioning consisting of busulfan and cyclophosphamide (in all cases from identical donor) and 11 were given a reduced intensity conditioning (8 from identical donor and 3 from mismatched donor). The cumulative incidence of graft failure was 8% (4% primary and 4% secondary graft failure). Transplant-related mortality for all patients was 42% (26% and 63% for patients transplanted following myeloablative or reduced intensity conditioning, respectively). As of October 31, 2009, 15 patients (11 in the myeloablative conditioning group and 4 in the reduced intensity conditioning group) are alive with complete hematologic recovery and no evidence of paroxysmal nocturnal hemoglobinuria following a median follow-up of 131 months (range 30-240). The 10-year Kaplan-Meier probability of disease-free survival was 57% for all patients: 65% for 23 patients transplanted from identical donor and 73% for 15 patients transplanted with myeloablative conditioning. No thromboembolic event nor recurrence of the disease were reported following transplant. CONCLUSIONS The findings of this study confirm that most patients with paroxysmal nocturnal hemoglobinuria may be definitively cured with hematopoietic stem cell transplantation.