Fludarabine and melphalan-based conditioning for patients with advanced hematological malignancies relapsing after a previous hematopoietic stem cell transplant.

Severe regimen-related toxicity often complicates second transplant procedures performed in patients with hematological malignancies that have relapsed after an initial hematopoietic stem cell (HSC) transplant. Therefore, we studied the safety and efficacy of a reduced-intensity fludarabine and melphalan based conditioning regimen in 11 patients who had relapsed following an autologous (n = 7) or allogeneic (n = 4) HSC transplant. All patients received allogeneic peripheral blood HSC from either an HLA-identical (n = 7) or an HLA-mismatched (n = 4) relative. Diagnoses included AML (n = 9), ALL (n = 1), or Hodgkin's disease (n = 1). Only one patient was in complete remission at the time of second transplant. The median interval between first transplant and relapse was 163 days (range 58-1885). Recipients of HLA-mismatched transplants received antithymocyte globulin in addition to fludarabine and melphalan as part of the conditioning regimen. All 11 patients received acute GVHD prophylaxis consisting of tacrolimus and methotrexate. Ten of 11 patients achieved hematopoietic engraftment with a median time to absolute neutrophil count >0.5 x 10(9)/l and to platelet count of >20 x 10(9)/l of 14 and 19 days, respectively. All engrafting patients achieved 100% donor chimerism on initial analysis, except for one with persistent leukemia at day +19. Two patients experienced grade 3 regimen-related toxicity, manifesting as acute renal failure. Acute GVHD grades 2-4 occurred in two recipients and chronic GVHD in four. The 100-day mortality from all causes was 36%. Ten of 11 patients (91%) died a median of 140 days (range 9-996) after the second transplant. The causes of death included relapse (n = 5), sepsis (n = 4), and idiopathic pneumonia syndrome (n = 1). One patient with AML survives in remission at 880 days post-transplant. We conclude that fludarabine- and melphalan-based conditioning promotes full donor chimerism, even following HLA-mismatched transplants. However, the regimen may be more beneficial when applied to patients undergoing allogeneic HSC transplantation earlier in their disease course.