Efficacy of Low Dose Clofarabine Plus Intermediate Dose Cytarabine In An Unselected AML Refractory/Relapsed Adult Population

Abstract 4349

Advanced AML in adult patients is a difficult challenge for hematologists with several unsuccessful approaches attempted during the last years. We tested the combination of the new nucleoside analogue Clofarabine in association with Cytarabine in a consecutive series of adult patients with advanced acute myeloid leukemia. From April 2007 to April 2010, 29 unselected advanced disease (not M3) acute myeloid leukemia (AML) patients were included in this multicenter study. There were 14 female and 15 male. Median age was 44 years (range 22–65). Twenty patients were in second or more advanced relapse and 9 had refractory disease to one or more chemotherapy regimens. Patients were treated with one cycle of five days clofarabine 22,5 mg/m²/day together with five days cytarabine 1 g/m²/day. The low dose (22,5 mg/m²) clofarabine was selected because of the burden of therapy that our patients had already received. In 19 patients gemtuzumab ozogamicin 6 mg/m² was added by Centre physician decision. Toxicity and remission status were defined according with WHO criteria. Partial remission was considered as improvement of peripheral blood count and reduction of bone marrow blasts > 50%). Toxicity: Grade IV haematology toxicity was recorded in all patients. Extra haematological toxicity was as follows: four patients presented ≥ grade III cutaneous toxicity, ten hepatic toxicity; three patients mucositis. Eight patients experienced a life threatening infection while in aplasia (six systemic septicemia and two pneumonia) which were ultimately fatal in four. Disease response: overall, 16 over 29 patients (55%) entered in complete remission (CR) and 4 in partial remission. Overall response rate was 69%. Outcome: over the sixteen patients who entered complete remission: 1 was lost at follow up, 1 relapsed, 1 was treated with azacitidine and 2 with another cycle of clofarabine. These three patients who received a not transplant intensification therapy are, so far, alive in complete remission. In eleven patients an allogeneic transplantation (with an unrelated or sibling donor) was performed as intensification therapy: to date, 8 of these 11 patients are alive in continuous complete remission after a median follow up of 6,5 months (2-36) while three died (two while in CR). Overall 11 (68%) of the 16 patients who entered into complete remission are alive and well. The new nucleoside analogue Clofarabine showed efficacy and synergism with cytarabine in treating AML. Even if 29/29 patients experienced grade IV haematological toxicity, infection rate was low and suitable considering the status of the disease. Extra haematological toxicity was acceptable and easily manageable. Considering the dismal outcome of these patients, we believe that intensification should be performed to allow a continuous complete remission. Indeed we were able to transplant 11/16 patients, eight of which maintained the complete remission after transplantation. Notably, 3 patients remained alive in complete remission out of a transplantation approach. It is not possible to draw any conclusion about the role, if any, of gemtuzumab ozogamicin. In summary, we showed that low dose clofarabine plus cytarabine because of efficacy and low extra-hematology toxicity could be a real bridge to allogeneic transplantation in these very poor risk pre-treated acute leukaemia patients. A longer follow up is awaited.