Relapse risk after FLAMSA RIC based allogeneic hematopoietic stem cell transplantation in heavily pretreated AML patients

Despite recent advances in the treatment of acute myeloid leukemia (AML), allogeneic hematopoietic stem cell transplantation (allo-HSCT) remains the only potentially curative treatment for many patients with high-risk AML [ 1 ]. Unfortunately, up to 30% of AML patients are primary refractory, and up to 46% of AML patients experience early relapse within 6 months after treatment completion [ 2 ]. For these patients, Schmid et al. explored an approach to improve outcomes by combining chemotherapy with fludarabine, amsacrine and cytarabine (FLAMSA) with a consecutive reduced intensity conditioning (RIC) allo-HSCT shortly after the end of cytoreductive chemotherapy followed by rapid tapering of immunosuppression and prophylactic donor lymphocyte infusions (DLI) in patients who did not develop a Graft-versus-Host Disease (GvHD) [ 3 ]. With 2-year overall survival (OS) rates of 42% and event-free survival (EFS) of 40%, this regimen is an established approach in high-risk AML patients [ 1 ]. However, the term high-risk AML is not well defined and changed with new disease classifications. The initial study as well as follow up trials included significant numbers of high-risk AML patients (defined by cytogenetics or delayed treatment-response) who were in morphological remission at the time of allo-HSCT [ 4 , 5 , 6 ]. Studies including mainly patients with active AML undergoing FLAMSA RIC do not solely focus on highly treatment-refractory patients [ 7 , 8 ].