Abstract
Advances in chemotherapy have improved the prognosis of patients with acute myeloid leukemia (AML), however, high-risk patients still have a poor outcome. In this category of patients, the only therapeutic strategy with curative potential remains allogeneic hematopoietic stem cell transplantation (allo-HSCT). With the aim to improve the effect of allo-HSCT by sequential use of chemotherapy followed by reduced intensity conditioning (RIC), we conducted a prospective pilot study in high-risk AML patients in first complete remission (CR1). The high-risk population included intermediate II [t(9;11)(p22;q23); MLLT3-MLL, cytogenetic abnormalities not classified as favorable or adverse] and unfavourable patients [inv(3)(q21q26.2) or t(3;3)(q21;q26.2); t(6;9)(p23;q34); t(v;11)(v;q23); MLL rearranged, -5 or del(5q); -7; abnl(17p); complex karyotype] (Dohner et al. Blood 2010), secondary AML, and patients requiring 2 induction courses to obtain CR. The chemotherapy sequential regimen consisted in fludarabine 30 mg/m2, high-dose cytarabine 2 g/m2, and amsacrine 100 mg/m2 from days -12 to -9 (FLAMSA). After 3 days of rest, RIC consisted of 4 Gy total-body irradiation (TBI) on day -5, cyclophosphamide (40 mg/kg with HLA-identical sibling, 60 mg/kg for unrelated or mismatched donors) on days -4 and -3, and rabbit antithymocyte globulin (ATG, Genzyme) (5 mg/kg total dose) from day -3 to day -1. As a new experimental approach, we replaced TBI by iv. busulfan (BU) (Busilvex, Pierre Fabre) 3.2 mg/kg/d during either 4 or 2 days according to patient age (>55 years) (from day -7 to -4 or from day -5 to -4). Peripheral-blood stem cells (PBSC) were preferred; bone marrow (BM) and cord blood (CB) were also accepted. Graft-versus-host disease (GvHD) prophylaxis consisted in ciclosporine from day -1, and mycophenolate mofetil (15 mg/kg bid), starting from day 0. In the absence of GvHD, MMF was discontinued by day+50 and ciclosporine was tapered from day +60 to +90. Except for cord blood transplantation, patients received 3 prophylactic increased doses of donor lymphocyte infusions (DLI) if they were in CR and GvHD-free at day +120 or 30 days after discontinuation of immunosuppressive agents starting at 1x106 CD3+ cells/kg. Between August 2010 and March 2013, 26 consecutive AML patients in CR1 were included; 11 males and 15 females with a median age at allo-HSCT of 55 years (range: 24-67), 19 (73%) were de novo AML and 7 (27%) secondary AML. According to cytogenetics and molecular markers, 22 (85%) were unfavourable and 4 (15%) were in intermediate II category. Before allo-HSCT, to reach CR1, 20 (77%) patients received one induction chemotherapy and 6 (23%) needed 2 inductions. Cell source was PBSC for 23 (88%) patients, CB for 2 and BM for 1 patient. Donors were 10/10 HLA matched siblings in 9 (35%) patients, 10/10 HLA matched unrelated in 8 (31%) patients and HLA mismatched for the rest of patients [unrelated 9/10 (n=7), CB 4/6 (n=2)]. For ABO compatibility, 13 (50%) were compatible, 5 (19%) had minor incompatibility and 8 (31%) had major incompatibility. For conditioning, 6 (23%) patients received TBI, 13 (50%) received 4 days BU and 7 (27%) received 2 days BU. After transplantation, 23 (88%) patients engrafted, 3 patients died early (1 at day 1 and 1 at day 2 both from septic shock; 1 at day 8 from pneumonia and pericardial effusion). At day 90 post-allo-HSCT, 18 (78%) showed total donor chimerism and 5 (22%) had mixed chimerism and all patients were in CR. There were 6/23 (26%) patients with acute GvHD [2 gr I, 2 gr II and 2 gr III] and 5/23 (22%) chronic GvHD [4 limited and 1 extensive], all before DLI. After a median follow-up of 9 months (range: 0.03-35), the 2-years probability of overall survival (OS) for the whole population was 58% (confidence interval: 47-69) (Figure 1a) and the 2 years cumulative incidence of relapse was 18% (confidence interval: 17-19). At the latest follow-up, 16/23 (70%) engrafted patients were alive, 4/23 (17%) patients relapsed and died later and 3/23 (13%) patients died from transplant related infectious complications. No statistical difference in terms of OS and relapse incidence was found between the 3 types of conditioning, (Figure 1b).
FLAMSA-RIC regimen followed by allo-HSCT showed promising results in high-risk CR1 AML patients. Because of some early severe infections, an efficient prophylactic anti-infectious strategy is recommended. The use of BU instead of TBI does not impact on transplant outcomes.
Disclosures:
No relevant conflicts of interest to declare.
PB2331 IMPACT OF PRETRANSPLANT CHEMOTHERAPY, GRAFT VERSUS HOST DISEASE PROPHYLAXIS, GENDER AND RISK GROUP ON ALLOGENEIC REDUCED INTENSITY CONDITIONING TRANSPLANTS FOR ELDERLY ACUTE MYELOID LEUKEMIA PATIENTS
