Outcome of Patients with Acute Myeloid Leukemia (AML) Undergoing Allogeneic Hematopoietic Stem Cell Transplantation (HSCT) Beyond First Complete Remission (CR1)
Authors: Evers Georg , Beelen Dietrich W. , Braess Jan , Sauerland Cristina , Kolb Hans-Jochem , Reichle Albrecht , Holler Ernst , Schwerdtfeger Rainer , Arnold Renate , Scheid Christoph , Krug Utz , Müller-Tidow Carsten , Schliemann Christoph , Mikesch Jan-Henrik , Lenz Georg , Wörmann Bernhard J. , Hiddemann Wolfgang , Berdel Wolfgang E. , Stelljes Matthias 
Published: October 2019

Abstract
Introduction
Despite substantial progress in the treatment of newly diagnosed AML, 20% to 40% of patients do not achieve remission with conventional induction chemotherapy. In addition, 50% to 70% of patients with CR1 are expected to relapse within 3 years. Currently, allogeneic HSCT is thought to be the most reliable curative option for patients with relapsed and/or refractory (r/r) disease. Compared to HSCT in CR1 allogeneic HSCT beyond CR1 is associated with lower survival rates. So far, different predictive factors influencing survival in r/r AML have been identified. However, pretransplantation variables delineating prognostic subgroups after allogeneic HSCT beyond CR1 are less well known and the total number of patients in trials addressing this issue has been limited.
Methods
We analyzed the outcome after allogeneic HSCT in non-APL-AML patients transplanted with either subsequent 2nd complete remission (CR2), r/r AML or with persisting cytopenia (PC, including patients with hematologic complete remission with incomplete hematologic recovery and patients with persisting bone marrow hypoplasia) after induction or salvage therapy. Of 3989 patients who enrolled into a multicenter clinical trial (AMLCG1999; NCT00266136) of the German Acute Myeloid leukemia Cooperative Group (AMLCG) we identified 498 subjects aged 17 to 74 years who underwent allogeneic HSCT beyond first CR. Before transplantation, all patients received first line treatment either with 6-Thioguanine, cyararabine, daunorubicin (TAD) and high-dose cytarabine, mitoxantrone (HAM) or HAM/HAM. After induction failure (n=97) or relapse (n=401) patients either received salvage chemotherapy (n=299) or directly underwent allogeneic HSCT (n=199). Overall survival (OS) and relapse free survival (RFS) after allogeneic HSCT were the main endpoints for this analysis. Kaplan-Meier analysis was performed to estimate survival probabilities in subgroups. Log-rank tests were used to compare survival groups. Relative hazard rates and differences in subgroups were calculated using cox regression analysis.
Results
At a median follow-up of 6.5 years for surviving patients, OS and RFS rates were 32% (95% CI 28-36%) and 30% (95% CI 26-34%), respectively. Subgroup analysis revealed an OS of 49% in 128 patients with allogeneic HSCT in CR2. In comparison, 73 patients who underwent allogeneic HSCT with PC after induction (n = 42) / salvage treatment (n = 31) and 297 patients with refractory disease (RD) exhibited an OS of 39% and 23%, respectively (Figure 1). The corresponding cumulative incidences (CI) at 1/6.5 years for death in remission after allogeneic HSCT were 25%/31% for patients transplanted in CR2, 29%/41% for patients transplanted with PC and 30%/46% for patients transplanted with RD, respectively. The cumulative incidence of relapse (CIR) after 6.5 years was 58% for patients transplanted with RD compared to 34% for patients transplanted in CR2 and 31% for patients with PC. Main prognostic factors for survival outcome were remission status prior to allogeneic HSCT and cytogenetic risk category at diagnosis. By contrast, patient age, donor, graft source, remission status after induction therapy and CMV status had no significant impact on survival outcome.
Conclusions
Long-term OS rates after allogeneic HSCT for patients with r/r AML are considered to range between 20 and 40%. Our analysis indicates that a substantial fraction of patients who received similar first line treatment within one prospective trial is able to achieve long term survival when transplanted beyond CR1. In addition, remission upon salvage therapy prior to allogeneic HSCT might be a relevant prognostic factor for patients with r/r AML. However, whether remission induction prior to HSCT can provide an overall survival benefit in patients with r/r disease is still elusive and is currently being evaluated in a prospective randomized clinical trial (ETAL3-ASAP; NCT02461537).

Disclosures
Beelen: Medac: Consultancy, Other: Travel Support. Scheid:Novartis: Honoraria, Research Funding; Janssen: Honoraria; Celgene: Honoraria; Takeda: Honoraria, Research Funding; BMS: Honoraria; Amgen: Honoraria. Lenz:Celgene Corp.: Consultancy, Honoraria, Other: Travel, Accomodations, Expenses, Research Funding, Speakers Bureau; Novartis: Research Funding; Roche: Consultancy, Honoraria, Other: Travel, Accomodations, Expenses, Research Funding; Bayer: Consultancy, Honoraria, Research Funding, Speakers Bureau; Janssen: Consultancy, Honoraria, Other: Travel, Accomodations, Expenses, Research Funding, Speakers Bureau; Gilead: Consultancy, Honoraria. Hiddemann:Bayer: Consultancy, Research Funding; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; F. Hoffman-La Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Stelljes:MSD: Consultancy; JAZZ: Honoraria; Amgen: Honoraria; Novartis: Honoraria; Pfizer: Consultancy, Honoraria, Research Funding.