No standard regimen exists for the treatment of patients with relapsed acute myeloid leukemia (AML), particularly in patients with a first remission duration of less than 1 year.
A number of agents have activity in recurrent AML.[2,3] A combination of mitoxantrone and cytarabine was successful in 50% to 60% of patients who experienced relapse after initially obtaining a complete remission (CR). Other studies using idarubicin and cytarabine or high-dose etoposide and cyclophosphamide reported similar results.[3,5,6,7] Mitoxantrone, etoposide, and cytarabine (MEC) demonstrated a CR induction rate of 55% in a population including 30 patients with relapsed AML, 28 patients with primary refractory AML, and 16 patients with secondary AML.[Level of evidence: 3iiiDiv] However, in a phase III Eastern Cooperative Oncology Group (ECOG) (E-2995) trial of MEC with or without PSC388, a multidrug resistance modulator, complete response (CR) was only 17% to 25% in a population including relapse at less than 6 months after first complete remission (CR), relapse after allogeneic or autologous bone marrow transplantation (BMT), second or greater relapse, primary induction failures, secondary AML, and high-risk myelodysplastic syndromes.[Level of evidence: 1iiDiv] Thus, treatments with new agents under clinical evaluation remain appropriate in eligible patients with recurrent AML.
Major pharmaceutical companies continually research and develop new cancer drugs and treatments, which must be shown to be safe and effective before doctors can prescribe them to patients. Through lymphomaclinical trials, researchers test the effects of new medications on a group of volunteers with lymphoma. Following a strict protocol and using carefully controlled conditions, researchers evaluate the drugs under development and measure the ability of the new drug to treat lymphoma, its safety,...
The immunotoxin gemtuzumab ozogamicin has been reported to have a 30% response rate in patients with relapsed AML expressing CD33. This included 16% of patients who achieved CRs and 13% of patients who achieved a CRp, a new response criteria defined for this trial. CRp refers to clearance of leukemic blasts from the marrow, with adequate myeloid and erythroid recovery but with incomplete platelet recovery (although platelet transfusion independence for at least 1 week was required). Unclear is whether the inadequate platelet recovery is the result of megakaryocyte toxic effects of gemtuzumab or subclinical residual leukemia. The long-term outcomes of patients who achieve CRp following gemtuzumab are not yet known. Gemtuzumab induces profound bone marrow aplasia similar to leukemia induction chemotherapy and also has substantial hepatic toxic effects, including hepatic venoocclusive disease.[11,12] The farnesyltransferase inhibitor tipifarnib (R115777) demonstrated a 32% response rate in a phase I study in patients with relapsed and refractory acute leukemia (two CRs and six partial responses in 24 patients treated) and has entered phase II trials. Clofarabine, a novel purine nucleoside analogue, induced CR in 8 out of 19 patients in first relapse as a single agent  and in seven out of 29 patients when administered in combination with intermediate-dose cytarabine.[Level of evidence: 3iiiDiv]