SUMMARY: The American Cancer Society estimates that for 2023, about 20,380 new cases of Acute Myeloid Leukemia (AML) will be diagnosed in the United States and 11,310 patients will die of the disease. AML can be considered as a group of heterogeneous diseases with different clinical behavior and outcomes. Cytogenetic analysis has been part of routine evaluation when caring for patients with AML. By predicting resistance to therapy, tumor cytogenetics will stratify patients, based on risk, and help manage them accordingly. Even though cytotoxic chemotherapy may lead to long term remission and cure in a minority of patients with favorable cytogenetics, patients with high-risk features such as unfavorable cytogenetics, molecular abnormalities, prior Myelodysplasia and advanced age, have poor outcomes with conventional chemotherapy alone.
Cytotoxic chemotherapy for AML often consists of induction therapy to achieve remission, followed by consolidation therapy. However, standard induction chemotherapy achieves Complete Remission in only 40-60% of AML patients older than 60 years of age, and majority of these patients will eventually relapse. This had been attributed to clonal evolution and epigenetic reprogramming, leading to aberrant DNA methylation, and persistence of leukemia-initiating cells. Patients with AML who are under age 55 with high-risk cytogenetics in first clinical remission, are considered for allogeneic Hematopoietic Cell Transplantation, as this has shown to offer survival advantage over conventional chemotherapy. Patients receive salvage chemotherapy, targeted therapy for FLT3-mutant and susceptible IDH mutant AML, or treatment with a BCL2 inhibitor and hypomethylating agent, if a donor is not readily available and a prolonged donor search is needed.
ASAP is a randomized Phase III trial, conducted in patients with an unfavorable risk AML who either had a poor response to first induction therapy or had a relapse after first induction therapy. This study enrolled AML patients with poor response after first induction therapy or relapsed AML, who were eligible for intensive chemotherapy and allogeneic Hematopoietic Cell Transplantation with either a matched sibling donor, an HLA-compatible (9 or more/10) unrelated donor, or ongoing donor search with two potential unrelated donors with 90% or more HLA-matching probability. This analysis included 276 patients, of whom 272 patients were treated per protocol. Patients were randomized 1:1 to a Remission Induction arm in which patients received Cytarabine 3 g/m2 IV (1 g/m2 for patients more than 60 years) twice daily on days 1-3 plus Mitoxantrone 10 mg/m2 IV on days 3-5 and subsequent allogeneic Hematopoietic Cell Transplantation (Remission Induction Strategy arm-N=134) or to Disease Control arm (DISC arm-N=138) prior to sequential conditioning and allogeneic Hematopoietic Cell Transplantation. Disease Control Strategy consisted primarily of watchful waiting, but low-dose Cytarabine and single doses of mitoxantrone were permitted for disease-control. The median age was 61 years and at randomization, 39 patients had matched sibling donor, 133 patients had an HLA-compatible unrelated donor with confirmed HLA-typing, and 104 patients had ongoing unrelated donor searches. The Primary endpoint was Disease Free Survival (DFS), defined as Complete Remission at day 56 after allogeneic Hematopoietic Cell Transplantation, although the statistical goal of the study was to show non-inferiority of the Disease Control arm. Major secondary endpoints included Overall Survival (OS) from randomization and Leukemia-Free Survival from Complete Remission at day 56. The median time to allogeneic Hematopoietic Cell Transplantation was 8 weeks in the Remission Induction Strategy arm and 4 weeks in the Disease Control arm. At 24 weeks from randomization 96% and 94% of patients had been transplanted in the Remission Induction Strategy arm and Disease Control arm, respectively.
The Primary endpoint was met with the Disease Control arm, which is the less intensive treatment strategy, meeting the Primary endpoint of DFS/Complete Remission at day 56 after allogeneic Hematopoietic Cell Transplantation. The Disease-Free Survival at day 56 was 81.3% in the Remission Induction Strategy arm and 84.1% in the Disease Control arm (P for noninferiority=0.047). Among patients who met the Primary endpoint, after a median follow-up from randomization of 37 months, there was no significant difference in the Leukemia-Free Survival or Overall Survival from day 56, in the Remission Induction Strategy arm and Disease Control arm. The Disease Control Strategy was also associated with significantly fewer Grade 3 or more adverse events, compared to the Remission Induction Strategy (23% versus 64%, P<0.001), and fewer mean number of days in hospital prior to transplant (19 versus 42 days, P<0.001).
The researchers concluded from this first randomized controlled trial that intensive remission induction chemotherapy prior to allogeneic Hematopoietic Cell Transplantation for patients with Relapsed/Refractory AML DID NOT result in a higher overall success rate and did not confer a survival advantage. It was noted that watchful waiting followed by sequential conditioning and allogeneic Hematopoietic Cell Transplantation resulted in comparable overall Complete Remission rates and survival. The researchers added that the data from this study support sequential conditioning and Hematopoietic Cell Transplantation, without prior remission-induction chemotherapy, whenever a donor is readily available. Further, the results of this study emphasize the importance of allogeneic Hematopoietic Cell Transplantation in patients with Relapsed/Refractory AML and stress the need for starting donor search at diagnosis.
In Patients with Relapsed/Refractory AML Sequential Conditioning and Immediate Allogeneic Stem Cell Transplantation (allo-HCT) Results in Similar Overall and Leukemia-Free Survival Compared to Intensive Remission Induction Chemotherapy Followed By Allo-HCT: Results from the Randomized Phase III ASAP Trial. Stelljes M, Middeke JM, Bug G, et al. 64th ASH Annual Meeting and Exposition December 10th-13,2022. Abstract#4.
